Technician using microscope for lab testing potential health threats

Lab Testing

Lab Testing

Last Section Update: 04/2023

1 Introduction

Summary and Quick Facts for Lab Testing

  • Having annual lab tests can alert you and your doctor to potential health threats and indicate age-related changes taking place in your body.
  • This protocol provides useful information about several common laboratory tests. Also, discover the downside of relying on so-called normal reference ranges, which may vary greatly from optimal levels.
  • When combined with routine doctor visits, the information provided in this protocol can help achieve a long and healthy life.

Lab Tests for Healthy Aging

Since 1983, Life Extension has suggested that aging people undergo yearly medical testing as part of a general health and longevity program. Having annual lab tests can alert you and your doctor to potential health threats and inform you about age-related changes taking place in your body.

Comprehensive lab testing can be obtained directly and inexpensively, without the need to go to a doctor’s office. This is fortunate because taking personal responsibility for monitoring and maintaining one’s health is crucial for anyone planning on pursuing a long and healthy life. Basic blood chemistry panels performed during routine yearly physicals may be insensitive to subtle age-related physiological changes that more robust blood testing can detect. For instance, the influence of sex hormones on wellbeing and general health is considerable, but basic conventional blood testing does not assess hormones.

Another problem with relying on conventional blood testing is that so-called “normal” reference ranges might not highlight subtle health issues (Lim 2015; Grote Beverborg 2015; Arslan 2016). Blood test reference ranges are established based on the normal distribution (ie, a bell curve) of results observed within a relatively small sample of “healthy” individuals from the population (Smellie 2006; Cox 1990; Hoermann 2012; Brooks 2012; Whitley 2002). However, a significant portion of the “healthy” population of modernized countries suffers suboptimal health related to poor diet and lifestyle. Thus, ranges normal for the population may not necessarily reflect truly healthy ranges. Standard reference ranges are useful for detecting overt pathologies, but may not be sensitive to mild deviations from ideal values among individuals interested in pursuing optimal health.

It is also critical to keep in mind that results from a single lab test are generally not definitive. This is especially true for lab values marginally outside normal ranges. By chance alone, about 5% of healthy people will have “abnormal” lab values (about 2.5% will be “low” and about 2.5% will be “high”). In fact, if a person does a comprehensive blood test yearly for several years, the likelihood that he or she will never have a single abnormal result is extremely low even if he or she does not have an actual health problem. Lab tests become much more informative when repeated over time so trends can be observed.

In this protocol, you will read about many important laboratory tests that can be undertaken regularly to inform your health outlook. For many of these tests, you will also learn that so-called “normal” reference ranges for results may be somewhat misleading, and discover ranges that Life Extension considers optimal.

This protocol does not contain an exhaustive list of laboratory tests; it only covers those deemed by Life Extension to be of importance to general healthy aging for most people. There are many more lab tests available, any number of which may be appropriate for specific medical concerns; an alphabetical list of all lab tests available through Life Extension is available on our website. Also, additional lab tests relevant to given health concerns are included in protocols on specific topics.

Note: Ranges and measurements discussed in this protocol apply to tests conducted by LabCorp. Tests conducted by other labs, such as Quest Diagnostics, may use different methods and thus have different reference values. Reference ranges based on testing at one lab should not be applied to results obtained via a different lab.

2 Limitations of "Normal" Lab Test References Ranges

Many studies over the years have found correlations between low-normal or high-normal lab results and health problems. In other words, test results at the low end or high end of the “normal” range have been associated with health risks. A few examples are outlined below, but many more abound.

For instance, high-normal glucose levels have been strongly and independently associated with cardio-metabolic disease risk (Shaye 2012; Nichols 2008; Shin 2011; Mortby 2013; Cherbuin 2012). Although fasting blood glucose under 99 mg/dL is considered normal by conventional medicine, levels above 86 mg/dL have been linked with health problems.

Thyroid hormone tests are another example where normal reference ranges may include levels that are suboptimal. While the normal range for TSH spans from 0.45 to 4.5 µIU/mL, levels higher than 2.5 µIU/mL have been linked to metabolic syndrome and high triglycerides (Ruhla 2010).

High-normal serum homocysteine levels have been associated with increased risk of atherosclerotic lesions in the carotid artery of healthy individuals (Willinek 2000). Yet another study, which followed 1,284 Korean men, concluded that high-normal urinary albumin to creatinine ratios predict the development of hypertension (Park 2014). However, these studies are typically ignored by conventional doctors who just rely on normal reference ranges.

A 2016 expert review concluded that the normal reference range for serum magnesium actually includes levels that indicate subclinical magnesium deficiency. These authors cited many trials that showed that magnesium levels that are in fact too low, but are usually considered acceptable, are associated with elevated risk of diabetes and metabolic disorders, high blood pressure, and cardiovascular disease, conditions that affect millions of Americans and shorten lifespan considerably (Costello 2016). Unfortunately, despite this recent expert review on serum magnesium, most health professionals still view a magnesium at the low end of the reference range as “normal” and take no corrective action.

Should You Eat Before a Blood Test?

Standard blood tests are usually done in the fasting state. However, a number of studies show that elevated after-meal blood levels of triglycerides and glucose are dangerous (DECODE Study Group 2001; Bansal 2007). The same is true for homocysteine, which may test normal after an overnight fast but elevate during a day of high meat ingestion.

Fasting glucose levels alone do not identify individuals with an increased risk of glucose-related disease because they do not detect dangerous after-meal glucose spikes (Group 1999; Nakagami 2004).

The current method of drawing blood only when “fasting” may not adequately reflect an individual’s glucose, triglyceride, homocysteine, and postprandial lipoprotein status over the course of a typical day.

By definition, fasting blood tests are conducted eight or more hours after your last meal. This method of only testing blood when in an artificial “fasting” state may not account for vital risk markers specific to you as an individual. In other words, after each meal, your blood sugar and triglycerides will rise, but should return to normal several hours afterwards.

Depending on the consistency and frequency of meals consumed, an individual may silently sustain tissue injuries throughout a typical day that are not detected when blood is drawn after an 8‒12 hour fast.

Conventional dogma is difficult to change, even when common sense and compelling science indicates a better approach.

Based on an accumulating volume of data, consider having your next blood draw 2‒4 hours after a meal, as close as possible to what you typically eat and drink on most days (including physical exercise) (Farukhi 2016; Eberly 2003; Bansal 2007; Nordestgaard 2007; Nordestgaard 2017; Avignon 1997).

More information about how fasting can impact blood test results is available in the May 2017 Life Extension Magazine article titled “Should You Eat Before a Blood Test?

3 Recommended Annual Testing

For otherwise healthy adults interested in annual preventive blood testing, Life Extension recommends the following tests. If any abnormalities are discovered on these tests, or if there is reason to suspect any other health issues, then additional tests should be undertaken as appropriate.


  • Chemistry Panel (metabolic panel with lipids)
  • Complete Blood Count
  • Testosterone (Total)
  • Free Testosterone
  • Dehydroepiandrosterone sulfate (DHEA-S)
  • Prostate Specific Antigen (PSA)
  • Estradiol (E2)
  • Homocysteine
  • C-reactive protein (High sensitivity)
  • TSH (Thyroid stimulating hormone)
  • Vitamin D, 25-Hydroxy
  • Hemoglobin A1C (HbA1C)
  • Apolipoprotein B (ApoB)


  • Chemistry Panel (metabolic panel with lipids)
  • Complete Blood Count
  • Testosterone (Total)
  • Free Testosterone
  • Dehydroepiandrosterone sulfate (DHEA-S)
  • Progesterone
  • Estradiol (E2)
  • Homocysteine
  • C-reactive protein (High sensitivity)
  • TSH (Thyroid stimulating hormone)
  • Vitamin D, 25-Hydroxy
  • Hemoglobin A1C (HbA1C)
  • Apolipoprotein B (ApoB)

4 Chemistry Panel and Complete Blood Count: The Most Common Blood Test

Hematocrit (whole blood)

Hematocrit measures the percentage of whole blood that is made up of red blood cells. Hematocrit decreases with age (Kubota 1991) and in anemia and increases in dehydration, and high values were also associated with the possibility of an increased risk for venous thrombosis (Schreijer 2010). Low or high hematocrit levels are associated with increased morbidity and mortality (Boffetta 2013; Paller 2012).

  • Reference Range:
    • Women 36.9-44.6%
    • Men 41.5-50.4%
  • LE’s Optimal Range: Upper end of the reference range

Hemoglobin (whole blood)

Hemoglobin is the iron-containing oxygen-transport protein in red blood cells. Its measurement aids in the diagnosis of various forms of anemia.

  • Reference Range:
    • Women 12.3-15.3 g/dL
    • Men 14-17.5 g/dL
  • LE’s Optimal Range: Upper end of the reference range

Sodium (serum)

Sodium is an essential electrolyte that is vital to normal cell function and to fluid, acid-base, and electrolyte balance. It also plays an important role in nerve and muscle function as well as nutrient transport (Strazzullo 2014). Serum sodium levels can reflect hydration status, kidney function, and other important medical information (BMJ Best Practice 2021; Wojszel 2020). A study published in early 2023 reported an association between serum sodium levels above 142 mmol/L in individuals aged 45-66 and an increased risk of chronic diseases. This study also reported an increased mortality risk associated with serum sodium levels above 144 mmol/L. The investigators remarked that their results suggest a serum sodium range of 138-142 mmol/L is associated with the lowest risk of chronic disease and death (Dmitrieva 2023).

    • Reference Range: 134-144 mmol/L
    • LE’s Optimal Range: 138-142 mmol/L

Calcium (serum)

This test is used to evaluate parathyroid function and calcium metabolism. Serum calcium is increased in hyperparathyroidism, hyperthyroidism, metabolic diseases of the bone, immobilization after trauma or osteoporosis, leukemia, lymphoma, and the use of certain diuretics (Goldstein 1990).

  • Reference Range: 8.6-10.3 mg/dL
  • LE’s Optimal Range: 9-10 mg/dL

Albumin (serum or plasma)

Increased albumin is found in cases of dehydration. Low albumin is found in patients receiving intravenous fluids, excessive hydration, liver disease, chronic alcoholism, certain chronic diseases such as cancer, Crohn’s disease, ulcerative colitis, chronic inflammatory diseases, infections, heart failure, skin diseases, burns, pregnancy, and oral contraceptive use.

  • Reference Range: 3.5-5.5 g/dL

Glucose (serum)

High blood glucose levels are associated with diabetes, neuropathy, eye problems, heart disease, and stroke. Glucose is the primary blood sugar used by cells to make energy. Glucose level is included in most chemistry panels. It is useful to have glucose tested with other measures such as insulin and hemoglobin A1C (HbA1C). This test may be done fasting or 2‒4 hours after eating. Both types of tests provide valuable information, though 2‒4 hours after a meal provides a more realistic assessment of the state of your blood in everyday life.

  • Reference Range: 65-99 mg/dL
  • LE’s Optimal Range: 80-86 mg/dL

Uric Acid (serum or plasma)

Uric acid is made from purines, which are made naturally in the body and also come from the diet (Schlesinger 2005). If uric acid is overproduced or the kidneys are unable to get rid of it, the elevated levels can result in joint pain, leading to a condition known as gout (George 2017). Uric acid is included in most chemistry panels.

  • Reference Range:
    • Women: 2.5-7.1 mg/dL
    • Men: 3.7-8.6 mg/dL
  • LE’s Optimal Range: <6.0 mg/dL (Desideri 2014)

Creatinine (serum or plasma)

Creatinine is a commonly used test to evaluate kidney function by measuring the rate of filtered fluid through the kidneys (Gowda 2010). It is included in most chemistry panels along with the BUN/creatinine ratio (which has a reference range of 9-20).

  • Reference Range:
    • Women: 0.57-1.0 mg/dL
    • Men: 0.76-1.27 mg/dL

Blood Urea Nitrogen (BUN) (serum or plasma)

Blood urea nitrogen (BUN) is an indicator of how well the liver and kidneys are functioning. BUN is included in most chemistry panels along with the BUN/creatinine ratio.

  • Reference Range:
    • 6-20 mg/dL (adults)
    • 8-23 mg/dL (>60 years)

Total Cholesterol/HDL Cholesterol Ratio (serum or plasma)

The total cholesterol to HDL cholesterol ratio is helpful in predicting an individual’s risk of developing atherosclerosis. The number is obtained by dividing the total cholesterol value by the value of the HDL cholesterol. (High ratios indicate higher risks of heart attacks; low ratios indicate lower risk.)

  • Reference Range: 0.0-5.0
  Men Women
½ average risk 3.4 3.3
Average risk 5.0 4.4
2x average risk 9.6 7.1
  • LE’s Optimal Range: <3.4

Triglycerides (serum or plasma)

Triglyceride levels are used to identify risk for developing coronary heart disease and if fat metabolism disorders are suspected.

  • Reference Range: 0-149 mg/dL
  • LE’s Optimal Range:
    • Fasting: <100 mg/dL (<80 mg/dL if any risk factors; <60 mg/dL if pre-existing cardiovascular disease);
    • Non-fasting: <116 mg/dL

Total Cholesterol (serum or plasma)

Total cholesterol is used to assess risk of coronary heart disease and stroke (Kinosian 1994; Ansell 2000; Foroughi 2013).

  • Reference Range: 100-199 mg/dL (over age 19)
  • LE’s Optimal Range: 160-180 mg/dL

HDL (serum or plasma)

High-density lipoprotein (HDL) is known as the “good” cholesterol because it helps transport cholesterol from cells to the liver for removal. Low HDL levels are used as a predictor of heart disease risk.

  • Reference Range: >39 mg/dL
  • LE’s Optimal Range: ≥50 mg/dL

LDL (serum or plasma)

Low-density lipoprotein (LDL) is known as the “bad” cholesterol because it carries cholesterol and fats from the liver to the rest of the body. Elevated LDL levels are used as a predictor of heart disease risk.

  • Reference Range: 0-99 mg/dL (over age 19)
  • LE’s Optimal Range:
    • Good: 80-100 mg/dL
    • Ideal: 40 – 79 mg/dL (Individuals with pre-existing CVD may need to target the lower end of the range, but that should be discussed with their physician)

Iron (serum, preferred)

Low levels of iron are associated with iron deficiency anemia. Anemia is associated with fatigue, low energy, and in some cases, can manifest as muscle aches and headaches. High levels of iron are associated with liver disease, kidney disease, and vitamin B6 deficiency (Prothro 1981; Gkamprela 2017; Mydlik 1997).

  • Reference Range:
    • Women:
      • 27-159 µg/dL (age 18-60)
      • 27-139 µg/dL (over age 60)
    • Men: 38-169 µg/dL (over age 17)
  • LE’s Optimal Range: 40-100 µg/dL

5 General Lab Tests

Gamma-globulin (serum)

Increased gamma-globulin is found in certain chronic inflammatory or autoimmune conditions, certain cancers, acute infections, chronic liver disease, and an overactive immune system.

  • Reference Range: 0.4-1.8 g/dL

Magnesium (serum)

Magnesium is one of the body’s most important minerals. It is required as a co-factor in hundreds of enzymatic processes within cells. It helps maintain normal muscle and nerve function, keeps heart rhythm steady, is necessary for healthy cardiovascular function, supports a healthy immune system, and keeps bones strong (Galland 1988; Jahnen-Dechent 2012; Castiglioni 2013). Magnesium also helps maintain healthy blood sugar and blood pressure levels and is involved in energy metabolism and protein synthesis (Cinar 2008; Veronese 2016; Guerrero-Romero 2009).

  • Reference Range: 1.6-2.3 mg/dL
  • LE’s Optimal Range: 2.07-2.31 mg/dL

Magnesium (RBC)

Red blood cell (RBC) magnesium is the most precise way to assess intracellular magnesium status, and free RBC magnesium has been shown to be inversely related with hypertension (Resnick 1984; Geiger 2012; Rosanoff 2005; Volpe 2013).

  • Reference Range: 4.2-6.8 mg/dL
  • LE’s Optimal Range: >6.0 mg/dL

Selenium (serum or plasma)

Selenium is a trace mineral and one of the body’s critical defenses against oxidative stress (Tinggi 2008; Rayman 2000). Selenium is incorporated into proteins to make selenoproteins, which are important free-radical quenching enzymes (Genc 2017). Selenium has also been shown to help regulate thyroid function and play a role in the immune system, DNA repair, and detoxification of heavy metals (Hoffmann 2008; Bera 2013; Whanger 1992; Ventura 2017).

  • Reference Range: 91-198 µg/L

Vitamin C (serum)

Vitamin C (ascorbic acid) is one of the body’s most important defenses against oxidative stress (Sorice 2014). Vitamin C is critical for protection against damaging free radicals, and is essential for tissue healing, immune function, fertility, cardiovascular health, and prevention of the common cold (Hemila 1992; Padh 1991; Bendich 1995; Chambial 2013). Low values occur in scurvy (Burhop 2018), malabsorption syndromes (Lykkesfeldt 2014), inflammatory bowel disease (Imes 1986), alcoholism (Majumdar 1981), pregnancy (IOM 1990), certain thyroid conditions (Moncayo 2008), and kidney failure (Granata 2015). Smokers have also been shown to have lower levels than non-smokers (Schectman 1989; Smith 1987).

  • Reference Range: 0.2-2.0 mg/dL
  • LE’s Optimal Range: >1.2 mg/dL

Vitamin D, 25-Hydroxy (serum)

Vitamin D is essential for human life, so much so that our bodies manufacture this critical nutrient in the skin upon sun exposure (Nair 2012). However, most people do not get enough sun exposure to maintain optimal levels of vitamin D in their bodies; risks of skin cancer and sun damage dissuade many of us from spending much time in the sun (Norman 2008).

But sun exposure is not the only way to increase vitamin D levels. Supplemental vitamin D efficiently boosts blood levels of vitamin D, which are typically measured as 25-hydroxyvitamin D. This is fortunate because research over many years has firmly established vitamin D as a key mediator of health throughout the body. Classically, vitamin D was thought to primarily support calcium homeostasis, but it is now known that vitamin D has many other crucial functions, including helping to balance the immune system (Bscheider 2016), suppress abnormal cell growth (Ness 2015; Watanabe 2015), and support brain health (Groves 2014).

Vitamin D deficiency has been associated with a host of diseases ranging from cancer (Kurylowicz 2007; Nabi 2015) and cardiovascular disease (Mozos 2015) to osteoporosis (Sahota 2000) and cognitive impairment (Etgen 2012). Thus, maintaining an optimal blood level of 25-hydroxyvitamin D is of paramount importance.

  • Reference Range: 30-100 ng/mL
  • LE’s Optimal Range: 50-80 ng/mL

Zinc (serum or plasma)

This test is used to evaluate zinc deficiencies since the body does not store this important mineral (Jurowski 2014). Levels may be low in malnutrition, malabsorption, alcoholism, extensive burns, some chronic and genetic conditions, and after the use of certain drugs (Prasad 1985), estrogen therapy (Herzberg 1996), and in anxiety, depression and stress (Gronli 2013; Russo 2011), and heart disease (Hashemian 2015). Zinc deficiencies may result in abnormal development (Black 1998), poor immune function (Prasad 2008), and hormone imbalances (Favier 1992). Additionally, people with low levels of zinc often report altered taste and smell (Tomita 1996), impaired night vision (Miao 2013), and emotional instability (Russo 2011).

  • Reference Range: 56-134 µg/dL
  • LE’s Optimal Range: >85 µg/dL

6 Anemia and Iron-Related Concerns

Ferritin (serum)

Iron is stored mostly in the liver bound to the protein ferritin. The amount of ferritin found in the blood shows how much iron is stored in the body (Knovich 2009).

  • Reference Range:
    • Women 15-150 ng/mL
    • Men 30-400 ng/mL
  • LE’s Optimal Range:
    • Women 50-100 ng/mL
    • Men 50-125 ng/mL

Vitamin B12 (serum)

Vitamin B12 plays an important role in producing cellular energy, for the formation of red blood cells, the functioning of the nervous system, including learning and memory (Kobe 2016; Grober 2013; Leishear 2012; O'Leary 2010). Vitamin B12 testing helps diagnose central nervous system disorders, anemia, and malabsorption syndromes.

  • Reference Range: 232-1245 pg/mL
  • LE’s Optimal Range: > 400 pg/mL

7 Blood Sugar

Fasting Glucose (serum)

High blood glucose levels are associated with diabetes, neuropathy, eye problems, heart disease, and stroke. Glucose is the primary blood sugar used by cells to make energy. Glucose level is included in most chemistry panels. It is useful to have glucose tested with other measures such as insulin and hemoglobin A1C (HbA1C). This test may be done fasting or 2‒4 hours after eating. Both types of tests provide valuable information, though 2‒4 hours after a meal provides a more realistic assessment of the state of your blood in everyday life.

  • Reference Range: 65-99 mg/dL
  • LE’s Optimal Range: 80-86 mg/dL

Glucose (2-Hour Postprandial) (serum or plasma)

Normally, blood glucose levels increase slightly after you eat. This increase causes the pancreas to release insulin so blood glucose levels do not get too high. Blood glucose levels that remain high over time can damage your eyes, kidneys, nerves, and blood vessels. This test measures blood glucose exactly two hours after eating.

  • Reference Range: 65-139 mg/dL
  • LE’s Optimal Range:
    • Good: 120-140 mg/dL
    • Ideal: 110-125 mg/dL (or an increase of no more than 40 mg/dL over fasting baseline)

Hemoglobin A1C (whole blood)

Hemoglobin A1C (HbA1C) evaluates long-term blood sugar control and correlates well with the risk of complications from diabetes (Sherwani 2016). Serum glucose reacts with important proteins in the body rendering them nonfunctional in a process called glycation. HbA1C is a reflection of this detrimental reaction (Florkowski 2013). Doctors often follow this blood test in diabetics to monitor disease progression and the effects of treatment.

  • Reference Range: 4.8-5.6 %
  • LE’s Optimal: < 5-5.4 %

Fasting Insulin (serum)

Insulin is a hormone secreted by the pancreas in response to eating carbohydrates. Insulin facilitates the transport of carbohydrates and sugars from the bloodstream into the cells. Insulin resistance, the hallmark of type II diabetes, occurs with excessive carbohydrate intake. In this case, insulin does not work optimally to drive glucose into the cells and tissues and results in high blood glucose. This test may be done fasting or 2‒6 hours after eating. Both ways provide valuable information, though 2‒6 hours after a meal provides a more realistic assessment of the state of your blood in everyday life.

  • Reference Range: 2.6-24.9 µIU/mL
  • LE’s Optimal Range: < 5.0-7.0 µIU/mL

Additional information about the importance of maintaining healthy blood sugar levels can be found in the Diabetes and Glucose Control protocol.

8 Adrenal Health

Cortisol (serum)

Cortisol is the major adrenal steroid hormone and is controlled by the pituitary gland and the hypothalamus. The body’s stress response increases cortisol in order to mobilize energy to manage and resolve the stressor.

Chronic stress can fatigue the adrenal gland which can disrupt its normal diurnal control over cortisol. This disruption can lead to symptoms like fatigue, weight gain, insomnia, depression, and anxiety.

Typically, cortisol is highest in the morning and drops during the day for most people (Chan 2010). Some people have a “reverse” cortisol rhythm or curve, where the levels are higher at night instead of being highest in the morning. Obtaining a morning and late afternoon cortisol value provides more information regarding an individual’s daily fluctuation in cortisol. 

Cortisol can be measured at a single point during the day, or in the morning and again in the afternoon to get a better idea of its fluctuations.

  • Reference range:
    • AM: 6.2-19.4 μg/dL
    • PM: 2.3-11.9 μg/dL

Dehydroepiandrosterone Sulfate (serum)

Dehydroepiandrosterone sulfate (DHEA-S) is a precursor for the sex steroids including estrogen and testosterone (Dimitrakakis 2009). DHEA-S and DHEA are primarily produced in the adrenal gland, and DHEA is produced by the ovary and testis (Crawford 2009; Maninger 2009). DHEA-S plays an important role in immune function and stress response (do Vale 2014; Buford 2008). Low DHEA-S levels are associated with a shorter lifespan, while higher levels are a predictor of longevity (Leowattana 2001; Rutkowski 2014).

  • Men’s Reference Ranges:
    • 20-24 yrs.: 164.3-530.5 µg/dL
    • 25-34 yrs.: 138.5-475.2 µg/dL
    • 35-44 yrs.: 102.6-416.3 µg/dL
    • 45-54 yrs.: 71.6-375.4 µg/dL
    • 55-64 yrs.: 48.9-344.2 µg/dL
    • 65-74 yrs.: 30.9-295.6 µg/dL
    • >74 yrs.: 20.8-226.4 µg/dL
  • LE’s Optimal Range for Men: 350-500 µg/dL
  • Women’s Reference Ranges:
    • 20-24 yrs.: 110.0-431.7 µg/dL
    • 25-34 yrs.: 84.8-378.0 µg/dL
    • 35-44 yrs.: 57.3-279.2 µg/dL
    • 45-54 yrs.: 41.2-243.7 µg/dL
    • 55-64 yrs.: 29.4-220.5 µg/dL
    • 65-74 yrs.: 20.4-186.6 µg/dL
    • >74 yrs.: 13.9-142.8 µg/dL
  • LE’s Optimal Range for Women: 275-400 µg/dL

9 Cardiovascular Health

Oxidized LDL

Oxidized LDL, the “bad” cholesterol that has been modified by oxidation, triggers inflammation leading to the formation of plaque in the arteries. High levels of oxidized LDL are associated with an increased risk of metabolic syndrome and coronary artery disease. Oxidized LDL is often measured with myeloperoxidase and/or F2-isoprostanes.


Myeloperoxidase (MPO) is an enzyme released by white blood cells when they attack. It causes death to microbes and amplifies inflammation and immune cell recruitment. This is great if there is a foreign invader, but terrible if it is happening in the arteries in response to oxidized LDL. It amplifies inflammation there and causes problems that increase plaque and often the worse kind of plaque, the soft vulnerable plaque that is prone to rupture. To make matters worse, MPO also oxidizes LDL, making it more plaque-promoting, and even oxidizes HDL (ie, good cholesterol) rendering it dysfunctional so it can no longer be helpful. These effects result in inflammation linked to plaque buildup inside the artery wall. Thus, MPO is a very interesting cardiovascular marker that is worth checking, especially in those with family history of cardiovascular disease or who make poor lifestyle choices.

F2-Isoprostanes (Urinary Test)

F2-Isoprostanes (F2-IsoPs) are a biomarker for oxidative stress. Oxidative stress occurs when free radicals react with neighboring molecules causing a cascade of damage in cells, which initiates destructive pathways that can lead to heart disease. F2-IsoPs may be elevated at the earliest stages of plaque development. F2-IsoPs are often measured along with oxidized LDL and/or MPO.

Lipoprotein (a) (serum or plasma)

The lipoprotein (a) test is used to measure excess small dense lipoprotein. Elevated lipoprotein (a) is a strong indicator of premature coronary disease and atherosclerotic vascular disease and is associated with increased risk of cardiac death in patients with coronary heart disease and stroke (Erqou 2009).

  • Reference Range: <75 nmol/L

Apolipoprotein B (ApoB)

The apolipoprotein B (apo B) blood test measures the number of potentially dangerous lipoprotein particles that can lead to the atherosclerotic process.

  • Reference Ranges:
    • Desirable: <90 mg/dL
    • Borderline High: 90-99 mg/dL
    • High: 100-130 mg/dL
    • Very High: >130 mg/dL
  • LE’s Optimal Range:
    • <80 mg/dL
    • <60 mg/dL (for those with high risk of arterial occlusion)

Coenzyme Q10 (plasma, frozen and protected from light)

Coenzyme Q10 (CoQ10) is produced by the human body and is necessary for the basic functioning of all cells. It is known to be highly concentrated in heart muscle cells due to the high energy requirements of this cell type (Fotino 2013).

CoQ10 blood levels are reported to decrease with age and to be low in patients with chronic diseases such as heart conditions, neuromuscular diseases, Parkinson disease, cancer, diabetes, and HIV/AIDS. Some prescriptions like statin medications can also lower CoQ10 levels (DiNicolantonio 2015; Artuch 2009; Mischley 2012; Cobanoglu 2011; Chai 2010; Folkers 1988; Shen 2015).

  • Reference Range: 0.37-2.20 µg/mL
  • LE’s Optimal Range: 3-7 µg/mL (those with cardiovascular disease or neurodegenerative disease likely need to be at the upper end of the optimal range)

Fibrinogen Activity (whole blood or plasma)

Fibrinogen is a key clotting protein that is an independent risk factor for cardiovascular disease and ischemic stroke (Franchini 2012; Montalescot 1998; Fukujima 1997).

  • Reference Range: 193-507 mg/dL (age 17 and above)
  • LE’s Optimal Range: 295-369 mg/dL

Homocysteine (plasma; serum is acceptable)

Homocysteine is an independent risk factor for coronary heart disease. High blood levels may directly damage the delicate endothelial cells that line the inside of arteries and result in vascular inflammation, blood clot formation, and arterial plaque rupture. Studies have shown that even moderate levels of homocysteine pose an increased risk for arterial plaque formation when compared with the lowest 20th percentile (<7.2 µmol/L) of population controls.

  • Reference Range: 0.0-15.0 µmol/L
  • LE’s Optimal Range:
    • Good: <12 µmol/L
    • Ideal: <8 µmol/L

Additional information about methods for maintaining cardiovascular health can be found in the Atherosclerosis and Cardiovascular Disease protocol.

10 Digestive Health

Small Intestinal Bacterial Overgrowth (SIBO) Breath Test – Lactulose

At-home breath tests can help determine some of the causes of digestive distress. Small intestinal bacterial overgrowth (SIBO) occurs when intestinal bacteria overgrow in the small intestine (Bures 2010; Dukowicz 2007; Bayeli 1999). This overgrowth can lead to excess production of gas and bacterial metabolites, causing bloating, flatulence, diarrhea, constipation, and cramping (Sachdev 2013). Lactulose has the advantage of detecting bacterial overgrowth throughout the small intestine, including the lower end where it more commonly occurs. Humans cannot digest or absorb lactulose, and only bacteria have the proper enzymes to break it down (Chen 2012). Lactulose passes unabsorbed through the normal small intestine, and when it reaches the colon, it is metabolized by bacteria to gases, including hydrogen, which can be detected (Simren 2006; Saad 2014).

Small Intestinal Bacterial Overgrowth (SIBO) Breath Test – Glucose

Although glucose is highly fermentable by bacteria, it is typically absorbed in the upper portion of the small intestine and thus, SIBO existing in the lower portion of the small intestines may be missed (Mattsson 2017; Chen 2016; Kiela 2016). The glucose breath test is more accurate than the lactulose breath test, and is considered more acceptable for diagnosing SIBO (Enko 2016; Rana 2014; Ghoshal 2011; Saad 2014). The test can also give false-positive results if the oral bacteria flora produces hydrogen (Mattsson 2017).

11 Kidney/Liver Health

Cystatin C (serum or plasma)

Cystatin-C is an indicator of kidney function (Murty 2013). It has been suggested that cystatin-C might predict patients with “preclinical” kidney dysfunction and patients with chronic kidney disease who are at a higher risk of complications (Shlipak 2006; Peralta 2011). Moreover, it can predict the risk of death and cardiovascular complications in patients with chronic kidney disease (Vigil 2014).

  • Reference Range: 0.62-1.16 mg/L
  • LE’s Optimal Range: <0.91 mg/L

Liver Enzymes: Alanine Transaminase (ALT/SGPT), Alkaline Phosphatase, Aspartate Aminotransferase (AST/SGOT), Lactate Dehydrogenase (LDH)

These liver enzymes are used to evaluate liver function. Both ALT and AST are abundant in the liver, and their levels increase with liver disease and sometimes with intense exercise (Giannini 2005). Personalized reference ranges are listed on laboratory results as they vary according to age and sex.

  • Reference Range:
    • ALT/SGPT: 0-44 IU/L
    • AST/SGOT: 0-40 IU/L
    • LDH:
      • Women: 119-226 IU/L (over 17 years)
      • Men: 121-224 IU/L (over 17 years)

Total Serum Protein

Total proteins are decreased in people with abnormal loss from the digestive tract, malnutrition, certain kidney diseases, or poor liver function.

  • Reference range: 6.0-8.5 g/dL

12 Thyroid Health

Thyroid-Stimulating Hormone (TSH) (serum)

Thyroid stimulating hormone (TSH) is produced and secreted by the pituitary gland and stimulates the thyroid to make T3 and T4. Increased TSH levels may indicate low thyroid function (Chakera 2012). When TSH is low, it may indicate high thyroid function (Girgis 2011). TSH is used as a first-line screening tool to assess thyroid disease; however, by itself it is insufficient, and needs to be evaluated in conjunction with other thyroid markers such as T3, T4, thyroid antibodies, and other tests (Iddah 2013; Ross 1989; Toft 2003).

  • Reference Range: 0.450-4.50 µIU/mL
  • LE’s Optimal Range: 1-2 µIU/mL

Free Tri-Iodothyronine (T3) (serum)

This test measures the amount of T3 available to the tissues, or free T3 (Sapin 2003). Many doctors believe that evaluating levels of free T3 is the best indicator of thyroid function (DeGroot 2016). Hypothyroidism is a condition where T3 blood levels are often (but not always) low (Koulouri 2013). This causes cellular dysfunction and metabolic disturbances (Sanyal 2016; Harper 2008; Brent 2012). Symptoms may include weight gain, constipation, dry skin, and hair loss. Hypothyroidism can lead to the development of chronic diseases, such as heart disease, and increases the risk of diabetes (Gronich 2015; Rodondi 2010; Chaker 2016).

  • Reference Range: 2.0-4.4 pg/mL (over 19 years)
  • LE’s Optimal Range: 3.4-4.2 pg/mL

Total Thyroxine (T4) (serum)

T4 is a hormone produced and secreted by the thyroid gland. At the tissue level, T4 is converted into the more active form of T3. For this reason, T4 is considered a measurement of total production of thyroid hormone. T4 blood levels are low in hypothyroidism, but may also be in the normal range (Chakera 2012). This causes cellular dysfunction and metabolic breakdown. Symptoms of hypothyroidism may include weight gain, constipation, dry skin, and hair loss. Low T4 levels may even lead to the development of chronic diseases such as heart disease and diabetes. T4 blood levels are elevated in hyperthyroidism, but may also be in the normal range or even low (Obuobie 2003; Santos Palacios 2012; Nygaard 2008). Symptoms of hyperthyroidism may include anxiety, insomnia, an increased heart rate, and bowel discomfort.

  • Reference Range: 4.5-12.0 µg/dL
  • LE’s Optimal Range:
    • Women (<60 yrs.) 9-11 µg/dL            
    • Women (>60 yrs.) 8.5-10.7 µg/dL
    • Men 8.5-10.5 µg/dL             

Free T4 (serum)

Proteins bind to T4 and carry it throughout the bloodstream. Once in the tissues, T4 is released from the proteins and free to convert into the more active form called T3. For this reason, many doctors believe that measuring free T4 is a good test for thyroid hormone production (Li 2014).

  • Reference Range: 0.82-1.77 ng/dL (over 19 years)
  • LE’s Optimal Range: 1.46-1.77 ng/dL

13 Inflammation

C-Reactive Protein, high sensitivity (serum or plasma)

The C-reactive protein (CRP) blood test measures the level of systemic inflammation. Uncontrolled systemic inflammation places you at risk for many degenerative diseases such as heart disease, stroke, and even increased cancer risk.

  • Reference Ranges:
    • Low risk <1.0 mg/L
    • Avg. risk 1.0-3.0 mg/L
    • High risk >3.0 mg/L
  • LE’s Optimal Range:
    • Women <1.0 mg/L
    • Men <0.55 mg/L

Interleukin-6 (IL-6) (serum)

This test is used to identify elevated levels of interleukin-6 (IL-6). Elevated IL-6 serum or plasma levels may occur in sepsis, autoimmune diseases, lymphomas, HIV/AIDS, alcoholic liver disease, cancer progression, Alzheimer disease, and in concert with infections or transplant rejection. Elevated levels of IL-6 may be associated with an increased risk of heart attack or stroke (Kanda 2004; Cojocaru 2009). It is a good idea to test values of IL-6 with other cytokines such as IL-1 beta, IL-8, and TNF-alpha.

  • Reference Range: 0-15.5 pg/mL

Interleukin-8 (IL-8) (serum)

This test is used to identify elevated levels of IL-8. Elevated IL-8 levels are observed in psoriasis, rheumatoid arthritis, chronic polyarthritis, cancer progression, and hepatitis C. It is a good idea to test measures of IL-8 with other cytokines such as IL-6, IL-1 beta, and TNF-alpha.

  • Reference Range: 0.0-66.1 pg/mL

Tumor Necrosis Factor-alpha (TNF-alpha) (serum)

This test is used to identify elevated levels of tumor necrosis factor-alpha. TNF-alpha levels may be elevated in sepsis, cachexia, HIV/AIDS, hepatitis C, transplant rejection, and various infectious and autoimmune diseases. It is a good idea to test measures of TNF-alpha with other cytokines such as IL-6, IL-8, and IL-1 beta.

  • Reference Range: 0.0-2.2 pg/mL

14 Men’s Health Concerns

Testosterone (Total) (serum)

Testosterone is a steroid hormone from the androgen group primarily secreted in the testes of males and the ovaries of females with small amounts also secreted by the adrenal glands (Burger 2002; Wood 2012).

Testosterone is a key anabolic steroid responsible for directing metabolism and tissue repair and regeneration (Demling 2005; Wu 2014; Yu 2014). In men, testosterone also plays a key role in the development of male reproductive tissues as well as promoting secondary sexual characteristics such as increased muscle and bone mass and hair growth.

In addition, testosterone is essential for overall health and wellness. Recent research has revealed the association between low testosterone and many age-related diseases. Conditions such as heart disease, osteoporosis, diabetes, and low libido are now thought to be attributed to what doctors call “low T” (Stanworth 2008; Rivas 2014; Huo 2016).

On average, an adult male has about 10 times more testosterone in the circulation than an adult female (Gentil 2016). However, women are far more sensitive to testosterone than men. Women with low testosterone may be more at risk for bone disease, dysfunction of the blood vessels, heart disease, muscle wasting, tiredness, and loss of libido (Lorenz 2017; Bolour 2005; Kaczmarek 2003; Rohr 2002; Rech 2016; Burger 2006; Bachmann 2006).

  • Reference Range for Men: 264-916 ng/dL (over age 18)
  • LE’s Optimal Range for Men: 600-900 ng/dL

Free Testosterone (serum)

Free testosterone is the biologically active form of this hormone measured in the blood. 

  • Reference Range for Men:
    • 20-29 yrs: 9.3-26.5 pg/mL
    • 30-39 yrs: 8.7-25.1 pg/mL
    • 40-49 yrs: 6.8-21.5 pg/mL
    • 50-59 yrs: 7.2-24.0 pg/mL
    • >59 yrs: 6.6-18.1 pg/mL
  • LE’s Optimal Range for Men: 15-25 pg/mL

Dihydrotestosterone (DHT) (serum or plasma, frozen)

Dihydrotestosterone (DHT) is a potent form of testosterone required for male sexual development (Roth 2011; Hiort 2013). In adults, DHT is the primary androgen in the prostate and in hair follicles (Anitha 2009). DHT levels are higher in men with male-pattern baldness and prostate dysfunction (Dhingra 2011; Wright 2010). Remember, women with higher levels of DHT can also lose their hair (Urysiak-Czubatka 2014).

Additionally, men and women on testosterone therapy should always check their testosterone blood level to make sure that it stays within an optimal range.

  • Reference Range for Men: 30-85 ng/dL
  • LE’s Optimal Range for Men: 30-50 ng/dL

Pregnenolone (serum or plasma, frozen)

Pregnenolone is sometimes called “the mother of all hormones.” All other steroids including testosterone and estrogens are derived from this important hormone (Velarde 2014). For this reason, optimal blood levels of pregnenolone are critical for a healthy hormone balance. Pregnenolone is also important for proper brain development, cognition, memory, and mood (Ducharme 2010; Mellon 2007; Brown 2014; Ritsner 2010). These dramatic effects on the brain explain why pregnenolone is known as a neuro-active steroid.

  • Reference Range for Men: <151 ng/dL
  • LE’s Optimal Range for Men: 125-175 ng/dL

Sex Hormone-Binding Globulin (SHBG) (serum)

Testosterone and estradiol circulate in the bloodstream, bound mostly to sex hormone-binding globulin (SHBG) and to some degree other proteins. Only a small fraction of the sex hormones are unbound, or "free," and thus biologically active and able to activate their receptors (Holst 2004; Rosner 1991; Hammond 2016).

SHBG levels should not be too low or too high. SHBG helps protect androgens like testosterone from being metabolized rapidly by the liver or excreted in the urine by the kidneys. If SHBG levels are too low, then testosterone will be metabolized and/or excreted too quickly and essentially wasted. If SHBG is too high, it decreases the active form of the hormone available to the tissues by binding too much of it up. Thus, bioavailability of sex hormones is influenced by the level of SHBG (Laurent 2016). High levels of insulin decrease SHBG level (Strain 1994). On the other hand, thyroid hormone and estrogen increase it (Serin 2001; Kalme 1999; Selva 2009).

  • Reference Ranges for Men:
    • 20-49 yrs.: 16.5-55.9 nmol/L
    • >49 yrs.: 19.3-76.4 nmol/L
  • LE’s Optimal Range for Men: ~30-40 nmol/L

Estradiol (E2) (serum)

Estradiol (E2) is the predominant sex hormone present in females and is also found at lower levels in men (Wise 2009; Schulster 2016). In men, high levels of estradiol are associated with abdominal fat, enlargement of the prostate, and cardiovascular risk. Also, low levels below 18 are associated with increased risk of fracture (Amin 2006).

  • Reference Range for Adult Men: 7.6-42.6 pg/mL
  • LE’s Optimal Range for Adult Men: 20-40 pg/mL

Total Estrogens (serum or plasma)

Total estrogen is a measurement of overall estrogen status. Estrogens are important regulators of reproductive and non-reproductive organs in men (Cooke 2017). They are involved in sexual development, lipid metabolism (Kula 2005), bone health (Vandenput 2009), and regulate body weight and adiposity (Rubinow 2017), immunity (Ercan 2017) and cardiovascular health (Sudhir 1999). The total estrogen test does not break down the individual estrogens but looks at the total body burden of estrogens and can even include exogenous estrogens such as phytoestrogens and xenoestrogens from the environment.

  • Reference Range for Men: 56-213 pg/mL

Prostate-Specific Antigen (PSA) (serum)

Prostate specific antigen (PSA) is produced exclusively by cells of the prostate gland (Lilja 1988; Sp 2013). Used in conjunction with the digital rectal examination, PSA is a useful screening test for benign prostatic hyperplasia (BPH) and prostate cancer. The real value of the PSA test is looking at trends over time versus a single PSA reading.

  • Reference Range: 0.0-4.0 ng/mL
  • LE’s Optimal Range: < 1.0 ng/mL

Alpha-fetoprotein (AFP) (serum)

Alpha-fetoprotein (a-FP, AFP) has several applications, the most important being in the management of testicular cancer.

  • Normal range: 0.0-8.3 ng/mL

Refer to Life Extension’s Male Hormone Restoration protocol for additional information about the benefits of these and other tests to overall health.

15 Women’s Health Concerns

Pregnenolone (serum or plasma, frozen)

Pregnenolone is sometimes called “the mother of all hormones.” All other steroids including testosterone and estrogens are derived from this important hormone (Velarde 2014).

  • Reference Range for Women: <151 ng/dL
  • LE’s Optimal Range for Women: 130-180 ng/dL

Estradiol (E2) (serum)

Estradiol (E2) is the predominant sex hormone present in women and is also found at lower levels in men (Wise 2009; Schulster 2016). It represents the most important estrogen, functionally, in humans (Chai 2014; Vermeulen 2002). E2 not only impacts reproductive and sexual functioning, but also affects other systems including bone health, heart health, the nervous system, and metabolism (Cui 2013; Bunt 1990).

E2 is the most active of all three estrogens commonly measured in a clinical setting (Wise 2009; Yang 2017). For women, it is important to compare the relationship between E2 and progesterone in evaluating menopausal symptoms such as hot flashes, mood disorders, and aging skin.

In both men and women, low levels of E2 are associated with osteoporosis (Vermeulen 2002; Shi 2017; Klaiber 1982; Carlsen 2000; Ettinger 1993; Quigley 1987).

  • Reference Range for Pre-Menopausal Women:
    • Follicular: 12.5-166.0 pg/mL
    • Ovulation: 85.8-498 pg/mL
    • Luteal: 43.8-211.0 pg/mL
  • LE’s Optimal Range: Varies with time in cycle, but maximum of 498 pg/mL
  • Reference Range for Postmenopausal Women: <6.0-54.7 pg/mL
  • LE’s Optimal Range for Menopausal Women:
    • Lowest levels shown to ameliorate symptoms: 30-50 pg/mL
    • With typical Bi-est: 80-100 pg/mL
    • Restoration of menstrual cycle (around day 21): 90-211 pg/mL

Total Estrogens (serum or plasma)

Total estrogen is a measure of overall estrogen status. In addition to their role in reproduction, estrogens affect several organs in the body. They are critical for the functioning of the nervous system, cardiovascular health (Navarro-Pardo 2017), and are involved in cognitive functioning (Sherwin 2003), metabolic pathways, muscle strength, the responses to injury and inflammation (Horstman 2012), and in maintaining the health of the urinary tract (Robinson 2003). Clinically estrogens are important in evaluating symptoms of menopause, cardiovascular risk, and bone health in aging women (Baker 2003; Wharton 2012; Riggs 2000). The total estrogen test does not break down the individual estrogens but looks at the total body burden of estrogens and can even include exogenous estrogens such as phytoestrogens and xenoestrogens from the environment.

  • Reference Range for Pre-Menopausal Women:
    • Day 1-10: 61-394 pg/mL
    • Day 11-20: 122-437 pg/mL
    • Day 21-30: 156-350 pg/mL
  • Optimal Ranges vary with time in cycle
  • Reference Range for Postmenopausal Women: <40 pg/mL
  • LE’s Optimal Range for Postmenopausal Women: 75-200 pg/mL (with hormone replacement therapy)

Progesterone (serum)

In both men and women, progesterone balances and offsets the powerful effects of estrogens. Some of the most common concerns of aging that women have include weight gain, insomnia, anxiety, depression, and migraines. For other women, even more debilitating conditions such as cancer, uterine fibroids, ovarian cysts, and osteoporosis may affect them at various stages of their lives.

As men age, complaints of weight gain, loss of libido, and prostate enlargement top their list of health concerns. Many physicians and scientists are becoming more aware of a common link between these conditions and an imbalance between two sex hormones: progesterone and estrogen.

  • Reference Ranges for Pre-Menopausal Women:
    • Follicular: 0.1-0.9 ng/mL
    • Luteal: 1.8-23.9 ng/mL
    • Ovulatory: 0.1-12.0 ng/mL
  • LE’s Optimal Range for Pre-Menopausal Women: 15-23 ng/mL at ~day 21
  • Reference Range for Postmenopausal Women: 0.0-0.1 ng/mL
  • LE’s Optimal Range for Postmenopausal Women: 2-6 ng/mL

Testosterone (Total) (serum)

Testosterone is a steroid hormone from the androgen group primarily secreted in the testes of males and the ovaries of females with small amounts also secreted by the adrenal glands (Burger 2002; Wood 2012). On average, an adult male has about 10 times more testosterone in the circulation than an adult female (Gentil 2016). However, women are far more sensitive to testosterone than men. Women with low testosterone may be more at risk for bone disease, dysfunction of the blood vessels, heart disease, muscle wasting, tiredness, and loss of libido (Lorenz 2017; Bolour 2005; Kaczmarek 2003; Rohr 2002; Rech 2016; Burger 2006; Bachmann 2006).

  • Reference Range for Women:
    • 13 – 71 ng/dL (20 – 30 years)
    • 8 – 60 ng/dL (31 – 40 years)
    • 4 – 50 ng/dL (41 – 60 years)
    • 3 – 67 ng/dL (61 – 80 years)
    • 2 – 45 ng/dL (>80 years)
  • LE’s Optimal Range for Women: 35 – 60 ng/dL (LabCorp ECLIA methodology)

Free Testosterone (serum)

Free testosterone is the biologically active form of this hormone measured in the blood. 

  • Reference Range for Women: 0.0-4.2 pg/mL (over age 19)
  • LE’s Optimal Range for Women: 2.1-4.2 pg/mL

Sex Hormone-Binding Globulin (SHBG) (serum)

Testosterone and estradiol circulate in the bloodstream, bound mostly to sex hormone-binding globulin (SHBG) and to some degree other proteins. Only a small fraction of the sex hormones is unbound, or "free," and thus biologically active and able to activate their receptors (Holst 2004; Rosner 1991; Hammond 2016).

SHBG levels should not be too low or too high. SHBG helps protect androgens like testosterone from being metabolized rapidly by the liver or excreted in the urine by the kidneys. If SHBG levels are too low, then testosterone will be metabolized and/or excreted too quickly and essentially wasted. If SHBG is too high, it decreases the active form of the hormone available to the tissues by binding too much of it up. Thus, bioavailability of sex hormones is influenced by the level of SHBG (Laurent 2016). High levels of insulin decrease SHBG level (Strain 1994). On the other hand, thyroid hormone and estrogen increase it (Serin 2001; Kalme 1999; Selva 2009).

  • Reference Ranges for Women:
    • 24.6-122.0 nmol/L (20-49 years)
    • 17.3-125.0 nmol/L (over age 49)
  • LE’s Optimal Range for Women: ~60-80 nmol/L

Refer to Life Extension’s Female Hormone Restoration protocol for additional information about the benefits of these and other tests to overall health.


  • Apr: Updated Life Extension’s optimal range for fasting insulin in Blood Sugar
  • Jan: Added section on sodium to Chemistry Panel and Complete Blood Count: The Most Common Blood Test


  • Jul: Updated section on total testosterone in Women's Health Concerns


  • Mar: Comprehensive update & review

Disclaimer and Safety Information

This information (and any accompanying material) is not intended to replace the attention or advice of a physician or other qualified health care professional. Anyone who wishes to embark on any dietary, drug, exercise, or other lifestyle change intended to prevent or treat a specific disease or condition should first consult with and seek clearance from a physician or other qualified health care professional. Pregnant women in particular should seek the advice of a physician before using any protocol listed on this website. The protocols described on this website are for adults only, unless otherwise specified. Product labels may contain important safety information and the most recent product information provided by the product manufacturers should be carefully reviewed prior to use to verify the dose, administration, and contraindications. National, state, and local laws may vary regarding the use and application of many of the therapies discussed. The reader assumes the risk of any injuries. The authors and publishers, their affiliates and assigns are not liable for any injury and/or damage to persons arising from this protocol and expressly disclaim responsibility for any adverse effects resulting from the use of the information contained herein.

The protocols raise many issues that are subject to change as new data emerge. None of our suggested protocol regimens can guarantee health benefits. Life Extension has not performed independent verification of the data contained in the referenced materials, and expressly disclaims responsibility for any error in the literature.

Amin S, Zhang Y, Felson DT, et al. Estradiol, testosterone, and the risk for hip fractures in elderly men from the Framingham Study. Am J Med. 2006;119(5):426-33.

Anitha B, Inamadar AC, Ragunatha S. Finasteride-its impact on sexual function and prostate cancer. Journal of cutaneous and aesthetic surgery.Jan 2009;2(1):12-16.

Ansell BJ. Cholesterol, stroke risk, and stroke prevention. Curr Atheroscler Rep.Mar 2000;2(2):92-96.

Arslan FD, Serdar M, Merve Ari E, Onur Oztan M, Hikmet Kozcu S, Tarhan H, . . . Yasar Ellidag H. Determination of Age-Dependent Reference Ranges for Coagulation Tests Performed Using Destiny Plus. Iranian journal of pediatrics. Jun 2016;26(3):e6177.

Artuch R, Salviati L, Jackson S, Hirano M, Navas P. Coenzyme Q10 deficiencies in neuromuscular diseases. Advances in experimental medicine and biology.2009;652:117-128.

Avignon A, Radauceanu A, Monnier L. Nonfasting plasma glucose is a better marker of diabetic control than fasting plasma glucose in type 2 diabetes. Diabetes care.Dec 1997;20(12):1822-1826.

Bachmann G, Oza D. Female androgen insufficiency. Obstetrics and gynecology clinics of North America.Dec 2006;33(4):589-598.

Baker L, Meldrum KK, Wang M, Sankula R, Vanam R, Raiesdana A, . . . Meldrum DR. The role of estrogen in cardiovascular disease. The Journal of surgical research.Dec 2003;115(2):325-344.

Bansal S, Buring JE, Rifai N, Mora S, Sacks FM, Ridker PM. Fasting compared with nonfasting triglycerides and risk of cardiovascular events in women. JAMA.Jul 18 2007;298(3):309-316.

Bayeli PF, Mariottini M, Lisi L, Ferrari P, Tedone F. [Guidelines on intestinal dysmicrobism (SIBO Small Intestine Bacterial Overgrowth)]. Minerva gastroenterologica e dietologica.Dec 1999;45(4):297-308.

Bendich A, Langseth L. The health effects of vitamin C supplementation: a review. Journal of the American College of Nutrition.Apr 1995;14(2):124-136.

Bera S, De Rosa V, Rachidi W, Diamond AM. Does a role for selenium in DNA damage repair explain apparent controversies in its use in chemoprevention? Mutagenesis. Mar 2013;28(2):127-134.

Black MM. Zinc deficiency and child development. The American journal of clinical nutrition.Aug 1998;68(2 Suppl):464s-469s.

BMJ Best Practice. Overview of acid-base and electrolyte disorders. Updated 9/7/2021. Accessed 1/19/2023.

offetta P, Islami F, Vedanthan R, Pourshams A, Kamangar F, Khademi H, . . . Malekzadeh R. A U-shaped relationship between haematocrit and mortality in a large prospective cohort study. International journal of epidemiology.Apr 2013;42(2):601-615.

Bolour S, Braunstein G. Testosterone therapy in women: a review. Int J Impot Res.Sep-Oct 2005;17(5):399-408.

Brent GA. Mechanisms of thyroid hormone action. The Journal of clinical investigation.Sep 2012;122(9):3035-3043.

Brooks JD. Translational genomics: the challenge of developing cancer biomarkers. Genome Res.Feb 2012;22(2):183-187.

Brown ES, Park J, Marx CE, Hynan LS, Gardner C, Davila D, . . . Holmes T. A randomized, double-blind, placebo-controlled trial of pregnenolone for bipolar depression. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology.Nov 2014;39(12):2867-2873.

Bscheider M, Butcher EC. Vitamin D immunoregulation through Dendritic Cells. Immunology. 2016;148(3):227-36.

Buford TW, Willoughby DS. Impact of DHEA(S) and cortisol on immune function in aging: a brief review. Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme.Jun 2008;33(3):429-433.

Bunt JC. Metabolic actions of estradiol: significance for acute and chronic exercise responses. Medicine and science in sports and exercise.Jun 1990;22(3):286-290.

Bures J, Cyrany J, Kohoutova D, Forstl M, Rejchrt S, Kvetina J, . . . Kopacova M. Small intestinal bacterial overgrowth syndrome. World journal of gastroenterology.Jun 28 2010;16(24):2978-2990.

Burger HG. Androgen production in women. Fertility and sterility. Apr 2002;77 Suppl 4:S3-5.

Burger HG, Papalia MA. A clinical update on female androgen insufficiency--testosterone testing and treatment in women presenting with low sexual desire. Sexual health.May 2006;3(2):73-78.

Burhop J, Gibson J, de Boer J, Heydarian C. Do You C What I C: Emergency Department Evaluation and Diagnosis of Pediatric Scurvy in an Autistic Child With a Restricted Diet. Pediatric emergency care.Jan 23 2018.

Carlsen CG, Soerensen TH, Eriksen EF. Prevalence of low serum estradiol levels in male osteoporosis. Osteoporosis international: a journal established as result of cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA.2000;11(8):697-701.

Castiglioni S, Cazzaniga A, Albisetti W, Maier JA. Magnesium and osteoporosis: current state of knowledge and future research directions. Nutrients.Jul 31 2013;5(8):3022-3033.

Chai NC, Peterlin BL, Calhoun AH. Migraine and estrogen. Current opinion in neurology.Jun 2014;27(3):315-324.

Chai W, Cooney RV, Franke AA, Shvetsov YB, Caberto CP, Wilkens LR, . . . Goodman MT. Plasma coenzyme Q10 levels and postmenopausal breast cancer risk: the multiethnic cohort study. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology.Sep 2010;19(9):2351-2356.

Chaker L, Ligthart S, Korevaar TI, Hofman A, Franco OH, Peeters RP, Dehghan A. Thyroid function and risk of type 2 diabetes: a population-based prospective cohort study. BMC medicine.Sep 30 2016;14(1):150.

Chakera AJ, Pearce SH, Vaidya B. Treatment for primary hypothyroidism: current approaches and future possibilities. Drug design, development and therapy.2012;6:1-11.

Chambial S, Dwivedi S, Shukla KK, John PJ, Sharma P. Vitamin C in disease prevention and cure: an overview. Indian J Clin Biochem.Oct 2013;28(4):314-328.

Chan S, Debono M. Replication of cortisol circadian rhythm: new advances in hydrocortisone replacement therapy. Ther Adv Endocrinol Metab.Jun 2010;1(3):129-138.

Chen L, Tuo B, Dong H. Regulation of Intestinal Glucose Absorption by Ion Channels and Transporters. Nutrients.Jan 14 2016;8(1).

Chen X, Zhai X, Kang Z, Sun X. Lactulose: an effective preventive and therapeutic option for ischemic stroke by production of hydrogen. Med Gas Res.Feb 6 2012;2:3.

Cherbuin N, Sachdev P, Anstey KJ. Higher normal fasting plasma glucose is associated with hippocampal atrophy: The PATH Study. Neurology.Sep 4 2012;79(10):1019-1026.

Cinar V, Polat Y, Mogulkoc R, Nizamlioglu M, Baltaci AK. The effect of magnesium supplementation on glucose and insulin levels of tae-kwan-do sportsmen and sedentary subjects. Pakistan journal of pharmaceutical sciences.Jul 2008;21(3):237-240.

Cobanoglu U, Demir H, Cebi A, Sayir F, Alp HH, Akan Z, . . . Bakan E. Lipid peroxidation, DNA damage and coenzyme Q10 in lung cancer patients--markers for risk assessment? Asian Pacific journal of cancer prevention: APJCP.2011;12(6):1399-1403.

Cojocaru IM, Cojocaru M, Tanasescu R, Iliescu I, Dumitrescu L, Silosi I. Expression of IL-6 activity in patients with acute ischemic stroke. Romanian journal of internal medicine = Revue roumaine de medecine interne.2009;47(4):393-396.

Cooke PS, Nanjappa MK, Ko C, Prins GS, Hess RA. Estrogens in Male Physiology. Physiological reviews.Jul 1 2017;97(3):995-1043.

Costello RB, Elin RJ, Rosanoff A, Wallace TC, Guerrero-Romero F, Hruby A, . . . Van Horn LV. Perspective: The Case for an Evidence-Based Reference Interval for Serum Magnesium: The Time Has Come. Advances in Nutrition: An International Review Journal.November 1, 2016 2016;7(6):977-993.

Cox RA, García-Palmieri, M.R. . Cholesterol, Triglycerides, and Associated Lipoproteins. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths; 1990. Chapter 31. Accessed 1/22/2018.

Crawford S, Santoro N, Laughlin GA, Sowers MF, McConnell D, Sutton-Tyrrell K, . . . Lasley B. Circulating dehydroepiandrosterone sulfate concentrations during the menopausal transition. The Journal of clinical endocrinology and metabolism. Aug 2009;94(8):2945-2951.

Cui J, Shen Y, Li R. Estrogen synthesis and signaling pathways during aging: from periphery to brain. Trends in molecular medicine.Mar 2013;19(3):197-209.

DECODE Study Group. Glucose tolerance and cardiovascular mortality: comparison of fasting and 2-hour diagnostic criteria. Archives of internal medicine.Feb 12 2001;161(3):397-405.

DeGroot LJ. Diagnosis and Treatment of Graves’ Disease. In: Endotext [Internet]. De Groot LJ, Chrousos G, Dungan K, et al., eds. South Dartmouth (MA):, Inc. Last updated 11/2/2016.Accessed 2/2/2018.

Demling RH. The role of anabolic hormones for wound healing in catabolic states. Journal of burns and wounds. Jan 17 2005;4:e2.

Desideri G, Castaldo G, Lombardi A, Mussap M, Testa A, Pontremoli R, . . . Borghi C. Is it time to revise the normal range of serum uric acid levels? European review for medical and pharmacological sciences.2014;18(9):1295-1306.

Dhingra N, Bhagwat D. Benign prostatic hyperplasia: An overview of existing treatment. Indian journal of pharmacology.Feb 2011;43(1):6-12.

Dimitrakakis C, Bondy C. Androgens and the breast. Breast cancer research: BCR.2009;11(5):212.

DiNicolantonio JJ, Bhutani J, McCarty MF, O'Keefe JH. Coenzyme Q10 for the treatment of heart failure: a review of the literature. Open heart.2015;2(1):e000326.

Dmitrieva NI, Gagarin A, Liu D, Wu CO, Boehm M. Middle-age high normal serum sodium as a risk factor for accelerated biological aging, chronic diseases, and premature mortality. eBioMedicine. 2023;87doi:10.1016/j.ebiom.2022.104404.

do Vale S, Selinger L, Martins JM, Gomes AC, Bicho M, do Carmo I, Escera C. The relationship between dehydroepiandrosterone (DHEA), working memory and distraction--a behavioral and electrophysiological approach. PloS one.2014;9(8):e104869.

Ducharme N, Banks WA, Morley JE, Robinson SM, Niehoff ML, Mattern C, Farr SA. Brain distribution and behavioral effects of progesterone and pregnenolone after intranasal or intravenous administration. European journal of pharmacology.Sep 1 2010;641(2-3):128-134.

Dukowicz AC, Lacy BE, Levine GM. Small intestinal bacterial overgrowth: a comprehensive review. Gastroenterology & hepatology.Feb 2007;3(2):112-122.

Eberly LE, Stamler J, Neaton JD. Relation of triglyceride levels, fasting and nonfasting, to fatal and nonfatal coronary heart disease. Archives of internal medicine.May 12 2003;163(9):1077-1083.

Enko D, Halwachs-Baumann G, Stolba R, Mangge H, Kriegshauser G. Refining small intestinal bacterial overgrowth diagnosis by means of carbohydrate specificity: a proof-of-concept study. Therapeutic advances in gastroenterology.May 2016;9(3):265-272.

Ercan A, Kohrt WM, Cui J, Deane KD, Pezer M, Yu EW, . . . Nigrovic PA. Estrogens regulate glycosylation of IgG in women and men. JCI insight.Feb 23 2017;2(4):e89703.

Erqou S, Kaptoge S, Perry PL, Di Angelantonio E, Thompson A, White IR, . . . Danesh J. Lipoprotein(a) concentration and the risk of coronary heart disease, stroke, and nonvascular mortality. JAMA.Jul 22 2009;302(4):412-423.

Etgen T, Sander D, Bickel H, Sander K, Forstl H. Vitamin D deficiency, cognitive impairment and dementia: a systematic review and meta-analysis. Dementia and geriatric cognitive disorders. 2012;33(5):297-305.

Ettinger B. Use of low-dosage 17 beta-estradiol for the prevention of osteoporosis. Clinical therapeutics.Nov-Dec 1993;15(6):950-962; discussion 949.

Farukhi Z, Mora S. Re-assessing the role of non-fasting lipids; a change in perspective. Annals of translational medicine.Nov 2016;4(21):431.

Favier AE. The role of zinc in reproduction. Hormonal mechanisms. Biological trace element research.Jan-Mar 1992;32:363-382.

Florkowski C. HbA1c as a Diagnostic Test for Diabetes Mellitus - Reviewing the Evidence. The Clinical biochemist. Reviews / Australian Association of Clinical Biochemists.Aug 2013;34(2):75-83.

Folkers K, Langsjoen P, Nara Y, Muratsu K, Komorowski J, Richardson PC, Smith TH. Biochemical deficiencies of coenzyme Q10 in HIV-infection and exploratory treatment. Biochemical and biophysical research communications.Jun 16 1988;153(2):888-896.

Foroughi M, Akhavanzanjani M, Maghsoudi Z, Ghiasvand R, Khorvash F, Askari G. Stroke and nutrition: a review of studies. International journal of preventive medicine.May 2013;4(Suppl 2):S165-179.

Fotino AD, Thompson-Paul AM, Bazzano LA. Effect of coenzyme Q(1)(0) supplementation on heart failure: a meta-analysis. The American journal of clinical nutrition.Feb 2013;97(2):268-275.

Franchini M, Lippi G. Fibrinogen replacement therapy: a critical review of the literature. Blood transfusion = Trasfusione del sangue.Jan 2012;10(1):23-27.

Fukujima MM, Martinez TL, Pinto LE, Auriemo Cdo R, de Andrade LA. [Fibrinogen as independent risk factor for ischemic stroke]. Arquivos de neuro-psiquiatria.Dec 1997;55(4):737-740.

Galland L. Magnesium and immune function: an overview. Magnesium.1988;7(5-6):290-299.

Geiger H, Wanner C. Magnesium in disease. Clin Kidney J.Feb 2012;5(Suppl 1):i25-i38.

Genc GE, Ozturk Z, Gumuslu S. Selenoproteins are involved in antioxidant defense systems in thalassemia. Metallomics. Sep 20 2017;9(9):1241-1250.

Gentil P, Steele J, Pereira MC, Castanheira RP, Paoli A, Bottaro M. Comparison of upper body strength gains between men and women after 10 weeks of resistance training. PeerJ.2016;4:e1627.

George C, Minter DA. Hyperuricemia. StatPearls. Treasure Island (FL): StatPearls Publishing LLC; 2017.

Ghoshal UC. How to interpret hydrogen breath tests. Journal of neurogastroenterology and motility.Jul 2011;17(3):312-317.

Giannini EG, Testa R, Savarino V. Liver enzyme alteration: a guide for clinicians. CMAJ: Canadian Medical Association journal = journal de l'Association medicale canadienne.Feb 1 2005;172(3):367-379.

Girgis CM, Champion BL, Wall JR. Current concepts in graves' disease. Ther Adv Endocrinol Metab.Jun 2011;2(3):135-144.

Gkamprela E, Deutsch M, Pectasides D. Iron deficiency anemia in chronic liver disease: etiopathogenesis, diagnosis and treatment. Annals of Gastroenterology: Quarterly Publication of the Hellenic Society of Gastroenterology.2017;30(4):405-413.

Goldstein DA. Chapter 143. Serum Calcium. In: Clinical Methods: The History, Physical, and Laboratory Examinations, 3rd edition. Walker HK, Hall WD, Hurst JW, eds. Boston: Butterworths; 1990.

Gowda S, Desai PB, Kulkarni SS, Hull VV, Math AA, Vernekar SN. Markers of renal function tests. North American journal of medical sciences.Apr 2010;2(4):170-173.

Granata S, Dalla Gassa A, Tomei P, Lupo A, Zaza G. Mitochondria: a new therapeutic target in chronic kidney disease. Nutrition & metabolism.2015;12:49.

Grober U, Kisters K, Schmidt J. Neuroenhancement with vitamin B12-underestimated neurological significance. Nutrients.Dec 12 2013;5(12):5031-5045.

Gronich N, Deftereos SN, Lavi I, Persidis AS, Abernethy DR, Rennert G. Hypothyroidism is a Risk Factor for New-Onset Diabetes: A Cohort Study. Diabetes care.Sep 2015;38(9):1657-1664.

Gronli O, Kvamme JM, Friborg O, Wynn R. Zinc deficiency is common in several psychiatric disorders. PloS one.2013;8(12):e82793.

Grote Beverborg N, Verweij N, Klip IT, van der Wal HH, Voors AA, van Veldhuisen DJ, . . . van der Meer P. Erythropoietin in the general population: reference ranges and clinical, biochemical and genetic correlates. PloS one.2015;10(4):e0125215.

Group DS. Glucose tolerance and mortality: comparison of WHO and American Diabetes Association diagnostic criteria. The DECODE study group. European Diabetes Epidemiology Group. Diabetes Epidemiology: Collaborative analysis Of Diagnostic criteria in Europe. Lancet.Aug 21 1999;354(9179):617-621.

Groves NJ, McGrath JJ, Burne TH. Vitamin D as a neurosteroid affecting the developing and adult brain. Annual review of nutrition. 2014;34:117-141.

Guerrero-Romero F, Rodriguez-Moran M. The effect of lowering blood pressure by magnesium supplementation in diabetic hypertensive adults with low serum magnesium levels: a randomized, double-blind, placebo-controlled clinical trial. Journal of human hypertension.Apr 2009;23(4):245-251.

Hammond GL. Plasma steroid-binding proteins: primary gatekeepers of steroid hormone action. The Journal of endocrinology.Jul 2016;230(1):R13-25.

Harper ME, Seifert EL. Thyroid hormone effects on mitochondrial energetics. Thyroid.Feb 2008;18(2):145-156.

Hashemian M, Poustchi H, Mohammadi-Nasrabadi F, Hekmatdoost A. Systematic review of zinc biochemical indicators and risk of coronary heart disease. ARYA atherosclerosis.Nov 2015;11(6):357-365.

Hemila H. Vitamin C and the common cold. The British journal of nutrition.Jan 1992;67(1):3-16.

Herzberg M, Lusky A, Blonder J, Frenkel Y. The effect of estrogen replacement therapy on zinc in serum and urine. Obstetrics and gynecology.Jun 1996;87(6):1035-1040.

Hiort O. The differential role of androgens in early human sex development. BMC medicine.Jun 24 2013;11:152.

Hoermann R, Midgley JE. TSH Measurement and Its Implications for Personalised Clinical Decision-Making. J Thyroid Res.2012;2012:438037.

Hoffmann PR, Berry MJ. The influence of selenium on immune responses. Molecular nutrition & food research.Nov 2008;52(11):1273-1280.

Holst JP, Soldin OP, Guo T, Soldin SJ. Steroid hormones: relevance and measurement in the clinical laboratory. Clinics in laboratory medicine. Mar 2004;24(1):105-118.

Horstman AM, Dillon EL, Urban RJ, Sheffield-Moore M. The role of androgens and estrogens on healthy aging and longevity. The journals of gerontology. Series A, Biological sciences and medical sciences. Nov 2012;67(11):1140-1152.

Huo S, Scialli AR, McGarvey S, Hill E, Tugertimur B, Hogenmiller A, . . . Fugh-Berman A. Treatment of Men for "Low Testosterone": A Systematic Review. PloS one.2016;11(9):e0162480.

Iddah MA, Macharia BN. Autoimmune thyroid disorders. ISRN Endocrinol.2013;2013:509764.

Imes S, Dinwoodie A, Walker K, Pinchbeck B, Thomson AB. Vitamin C status in 137 outpatients with Crohn's disease. Effect of diet counseling. Journal of clinical gastroenterology.Aug 1986;8(4):443-446.

IOM. Institute of Medicine; Committee on Nutritional Status During Pregnancy and Lactation. Chapter 18: Water-Soluble Vitamins. In: Nutrition During Pregnancy: Part I Weight Gain: Part II Nutrient Supplements. Washington (DC): National Academies Press (US); 1990. Accessed 1/28/2018.

Jahnen-Dechent W, Ketteler M. Magnesium basics. Clinical kidney journal.Feb 2012;5(Suppl 1):i3-i14.

Jurowski K, Szewczyk B, Nowak G, Piekoszewski W. Biological consequences of zinc deficiency in the pathomechanisms of selected diseases. Journal of biological inorganic chemistry: JBIC: a publication of the Society of Biological Inorganic Chemistry.Oct 2014;19(7):1069-1079.

Kaczmarek A, Reczuch K, Majda J, Banasiak W, Ponikowski P. The association of lower testosterone level with coronary artery disease in postmenopausal women. International journal of cardiology.Jan 2003;87(1):53-57.

Kalme T, Loukovaara M, Koistinen R, Koistinen H, Angervo M, Leinonen P, Seppala M. Estradiol increases the production of sex hormone-binding globulin but not insulin-like growth factor binding protein-1 in cultured human hepatoma cells. Fertility and sterility.Aug 1999;72(2):325-329.

Kanda T, Takahashi T. Interleukin-6 and cardiovascular diseases. Japanese heart journal.Mar 2004;45(2):183-193.

Kiela PR, Ghishan FK. Physiology of Intestinal Absorption and Secretion. Best Pract Res Clin Gastroenterol.Apr 2016;30(2):145-159.

Kinosian B, Glick H, Garland G. Cholesterol and coronary heart disease: predicting risks by levels and ratios. Annals of internal medicine.Nov 1 1994;121(9):641-647.

Klaiber EL, Broverman DM, Haffajee CI, Hochman JS, Sacks GM, Dalen JE. Serum estrogen levels in men with acute myocardial infarction. The American journal of medicine.Dec 1982;73(6):872-881.

Knovich MA, Storey JA, Coffman LG, Torti SV, Torti FM. Ferritin for the clinician. Blood reviews.May 2009;23(3):95-104.

Kobe T, Witte AV, Schnelle A, Grittner U, Tesky VA, Pantel J, . . . Floel A. Vitamin B-12 concentration, memory performance, and hippocampal structure in patients with mild cognitive impairment. The American journal of clinical nutrition.Apr 2016;103(4):1045-1054.

Koulouri O, Moran C, Halsall D, Chatterjee K, Gurnell M. Pitfalls in the measurement and interpretation of thyroid function tests. Best practice & research. Clinical endocrinology & metabolism.Dec 2013;27(6):745-762.

Kubota K, Shirakura T, Orui T, Muratani M, Maki T, Tamura J, Morita T. [Changes in the blood cell counts with aging]. Nihon Ronen Igakkai zasshi. Japanese journal of geriatrics.Jul 1991;28(4):509-514.

Kula K, Walczak-Jedrzejowska R, Slowikowska-Hilczer J, Wranicz JK, Kula P, Oszukowska E, Marchlewska K. [Important functions of estrogens in men--breakthrough in contemporary medicine]. Przeglad lekarski. 2005;62(9):908-915.

Kurylowicz A, Bednarczuk T, Nauman J. [The influence of vitamin D deficiency on cancers and autoimmune diseases development]. Endokrynologia Polska. Mar-Apr 2007;58(2):140-152.

Laurent MR, Helsen C, Antonio L, Schollaert D, Joniau S, Vos MJ, . . . Claessens F. Effects of sex hormone-binding globulin (SHBG) on androgen bioactivity in vitro. Molecular and cellular endocrinology.Dec 5 2016;437:280-291.

Leishear K, Boudreau RM, Studenski SA, Ferrucci L, Rosano C, de Rekeneire N, . . . Strotmeyer ES. Relationship between vitamin B12 and sensory and motor peripheral nerve function in older adults. J Am Geriatr Soc.Jun 2012;60(6):1057-1063.

Leowattana W. DHEA(S): the fountain of youth. Journal of the Medical Association of Thailand = Chotmaihet thangphaet.Oct 2001;84 Suppl 2:S605-612.

Li H, Yuan X, Liu L, Zhou J, Li C, Yang P, . . . Qu S. Clinical evaluation of various thyroid hormones on thyroid function. International journal of endocrinology.2014;2014:618572.

Lilja H, Abrahamsson PA. Three predominant proteins secreted by the human prostate gland. Prostate.1988;12(1):29-38.

Lim E, Miyamura J, Chen JJ. Racial/Ethnic-Specific Reference Intervals for Common Laboratory Tests: A Comparison among Asians, Blacks, Hispanics, and White. Hawai'i journal of medicine & public health: a journal of Asia Pacific Medicine & Public Health.Sep 2015;74(9):302-310.

Lorenz TK, Heiman JR, Demas GE. Testosterone and immune-reproductive tradeoffs in healthy women. Hormones and behavior.Feb 2017;88:122-130.

Lykkesfeldt J, Michels AJ, Frei B. Vitamin C. Adv Nutr.Jan 1 2014;5(1):16-18.

Majumdar SK, Patel S, Shaw GK, O'Gorman P, Thomson AD. Vitamin C utilization status in chronic alcoholic patients after short-term intravenous therapy. International journal for vitamin and nutrition research. Internationale Zeitschrift fur Vitamin- und Ernahrungsforschung. Journal international de vitaminologie et de nutrition. 1981;51(3):274-278.

Maninger N, Wolkowitz OM, Reus VI, Epel ES, Mellon SH. Neurobiological and neuropsychiatric effects of dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS). Frontiers in neuroendocrinology.Jan 2009;30(1):65-91.

Mattsson J, Minaya MT, Monegro M, Lebwohl B, Lewis SK, Green PH, Stenberg R. Outcome of breath tests in adult patients with suspected small intestinal bacterial overgrowth. Gastroenterology and hepatology from bed to bench.Summer 2017;10(3):168-172.

Mellon SH. Neurosteroid regulation of central nervous system development. Pharmacology & therapeutics.Oct 2007;116(1):107-124.

Miao X, Sun W, Miao L, Fu Y, Wang Y, Su G, Liu Q. Zinc and diabetic retinopathy. J Diabetes Res.2013;2013:425854.

Mischley LK, Allen J, Bradley R. Coenzyme Q10 deficiency in patients with Parkinson's disease. Journal of the neurological sciences.Jul 15 2012;318(1-2):72-75.

Moncayo R, Kroiss A, Oberwinkler M, Karakolcu F, Starzinger M, Kapelari K, . . . Moncayo H. The role of selenium, vitamin C, and zinc in benign thyroid diseases and of selenium in malignant thyroid diseases: Low selenium levels are found in subacute and silent thyroiditis and in papillary and follicular carcinoma. BMC endocrine disorders.Jan 25 2008;8:2.

Montalescot G, Collet JP, Choussat R, Thomas D. Fibrinogen as a risk factor for coronary heart disease. European heart journal.Jul 1998;19 Suppl H:H11-17.

Mortby ME, Janke AL, Anstey KJ, Sachdev PS, Cherbuin N. High "normal" blood glucose is associated with decreased brain volume and cognitive performance in the 60s: the PATH through life study. PloS one. 2013;8(9):e73697.

Mozos I, Marginean O. Links between Vitamin D Deficiency and Cardiovascular Diseases. BioMed research international. 2015;2015:109275.

Murty MS, Sharma UK, Pandey VB, Kankare SB. Serum cystatin C as a marker of renal function in detection of early acute kidney injury. Indian J Nephrol.May 2013;23(3):180-183.

Mydlik M, Derzsiova K, Zemberova E. Metabolism of vitamin B6 and its requirement in chronic renal failure. Kidney international. Supplement.Nov 1997;62:S56-59.

Nabi G, Hobani Y, Sarwat M. High prevalence of vitamin D deficiency and cancer in Saudi Arabian populations: Can we hypothesize a link? Medical hypotheses. Aug 2015;85(2):117-119.

Nair R, Maseeh A. Vitamin D: The "sunshine" vitamin. Journal of pharmacology & pharmacotherapeutics.Apr 2012;3(2):118-126.

Nakagami T. Hyperglycaemia and mortality from all causes and from cardiovascular disease in five populations of Asian origin. Diabetologia.Mar 2004;47(3):385-394.

Navarro-Pardo E, Holland CA, Cano A. Sex Hormones and Healthy Psychological Aging in Women. Frontiers in aging neuroscience.2017;9:439.

Ness RA, Miller DD, Li W. The role of vitamin D in cancer prevention. Chinese journal of natural medicines. Jul 2015;13(7):481-497.

Nichols GA, Hillier TA, Brown JB. Normal fasting plasma glucose and risk of type 2 diabetes diagnosis. The American journal of medicine.Jun 2008;121(6):519-524.

Nordestgaard BG. A Test in Context: Lipid Profile, Fasting Versus Nonfasting. J Am Coll Cardiol.Sep 26 2017;70(13):1637-1646.

Nordestgaard BG, Benn M, Schnohr P, Tybjaerg-Hansen A. Nonfasting triglycerides and risk of myocardial infarction, ischemic heart disease, and death in men and women. JAMA.Jul 18 2007;298(3):299-308.

Norman AW. From vitamin D to hormone D: fundamentals of the vitamin D endocrine system essential for good health. The American journal of clinical nutrition. Aug 2008;88(2):491s-499s.

Nygaard B. Hyperthyroidism (primary). BMJ Clin Evid.Mar 25 2008;2008.

O'Leary F, Samman S. Vitamin B12 in health and disease. Nutrients.Mar 2010;2(3):299-316.

Obuobie K, Jones MK. Hyperthyroidism with low thyroid hormone. J R Soc Med.Apr 2003;96(4):185-186.

Padh H. Vitamin C: newer insights into its biochemical functions. Nutrition reviews.Mar 1991;49(3):65-70.

Paller CJ, Shiels MS, Rohrmann S, Menke A, Rifai N, Nelson WG, . . . Dobs AS. Association between sex steroid hormones and hematocrit in a nationally representative sample of men. Journal of andrology.Nov-Dec 2012;33(6):1332-1341.

Park SK, Moon SY, Oh CM, Ryoo JH, Park MS. High normal urine albumin-to-creatinine ratio predicts development of hypertension in Korean men. Circulation journal: official journal of the Japanese Circulation Society.2014;78(3):656-661.

Peralta CA, Katz R, Sarnak MJ, Ix J, Fried LF, De Boer I, . . . Shlipak MG. Cystatin C identifies chronic kidney disease patients at higher risk for complications. Journal of the American Society of Nephrology: JASN. Jan 2011;22(1):147-155.

Prasad AS. Clinical manifestations of zinc deficiency. Annu Rev Nutr.1985;5:341-363.

Prasad AS. Zinc in human health: effect of zinc on immune cells. Molecular medicine (Cambridge, Mass.).May-Jun 2008;14(5-6):353-357.

Prothro J. Any depression from OC-altered vitamin B6 levels? [Answer to question of Jan Marquand]. Contraceptive technology update.Sep 1981;2(9):121-123.

Quigley ME, Martin PL, Burnier AM, Brooks P. Estrogen therapy arrests bone loss in elderly women. American journal of obstetrics and gynecology.Jun 1987;156(6):1516-1523.

Rana SV, Malik A. Hydrogen breath tests in gastrointestinal diseases. Indian journal of clinical biochemistry: IJCB.Oct 2014;29(4):398-405.

Rayman MP. The importance of selenium to human health. Lancet (London, England).Jul 15 2000;356(9225):233-241.

Rech CM, Clapauch R, de Souza M, Bouskela E. Low testosterone levels are associated with endothelial dysfunction in oophorectomized early postmenopausal women. European journal of endocrinology / European Federation of Endocrine Societies.Mar 2016;174(3):297-306.

Resnick LM, Gupta RK, Laragh JH. Intracellular free magnesium in erythrocytes of essential hypertension: relation to blood pressure and serum divalent cations. Proceedings of the National Academy of Sciences of the United States of America.Oct 1984;81(20):6511-6515.

Riggs BL. The mechanisms of estrogen regulation of bone resorption. The Journal of clinical investigation.Nov 2000;106(10):1203-1204.

Ritsner MS, Gibel A, Shleifer T, Boguslavsky I, Zayed A, Maayan R, . . . Lerner V. Pregnenolone and dehydroepiandrosterone as an adjunctive treatment in schizophrenia and schizoaffective disorder: an 8-week, double-blind, randomized, controlled, 2-center, parallel-group trial. The Journal of clinical psychiatry.Oct 2010;71(10):1351-1362.

Rivas AM, Mulkey Z, Lado-Abeal J, Yarbrough S. Diagnosing and managing low serum testosterone. Proceedings (Baylor University. Medical Center).Oct 2014;27(4):321-324.

Robinson D, Cardozo LD. The role of estrogens in female lower urinary tract dysfunction. Urology.Oct 2003;62(4 Suppl 1):45-51.

Rodondi N, den Elzen WP, Bauer DC, Cappola AR, Razvi S, Walsh JP, . . . Gussekloo J. Subclinical hypothyroidism and the risk of coronary heart disease and mortality. JAMA.Sep 22 2010;304(12):1365-1374.

Rohr UD. The impact of testosterone imbalance on depression and women's health. Maturitas.Apr 15 2002;41 Suppl 1:S25-46.

Rosanoff A. [Magnesium and hypertension]. Clin Calcium.Feb 2005;15(2):255-260.

Rosner W. Plasma steroid-binding proteins. Endocrinology and metabolism clinics of North America.Dec 1991;20(4):697-720.

Ross DS, Ardisson LJ, Meskell MJ. Measurement of thyrotropin in clinical and subclinical hyperthyroidism using a new chemiluminescent assay. The Journal of clinical endocrinology and metabolism.Sep 1989;69(3):684-688.

Roth MY, Page ST. A role for dihydrotestosterone treatment in older men? Asian journal of andrology.Mar 2011;13(2):199-200.

Rubinow KB. Estrogens and Body Weight Regulation in Men. Advances in experimental medicine and biology.2017;1043:285-313.

Ruhla S, Weickert MO, Arafat AM, Osterhoff M, Isken F, Spranger J, . . . Mohlig M. A high normal TSH is associated with the metabolic syndrome. Clinical endocrinology.May 2010;72(5):696-701.

Russo AJ. Decreased zinc and increased copper in individuals with anxiety. Nutrition and metabolic insights.2011;4:1-5.

Rutkowski K, Sowa P, Rutkowska-Talipska J, Kuryliszyn-Moskal A, Rutkowski R. Dehydroepiandrosterone (DHEA): hypes and hopes. Drugs.Jul 2014;74(11):1195-1207.

Saad RJ, Chey WD. Breath testing for small intestinal bacterial overgrowth: maximizing test accuracy. Clinical gastroenterology and hepatology: the official clinical practice journal of the American Gastroenterological Association.Dec 2014;12(12):1964-1972; quiz e1119-1920.

Sachdev AH, Pimentel M. Gastrointestinal bacterial overgrowth: pathogenesis and clinical significance. Therapeutic advances in chronic disease.Sep 2013;4(5):223-231.

Sahota O. Osteoporosis and the role of vitamin D and calcium-vitamin D deficiency, vitamin D insufficiency and vitamin D sufficiency. Age Ageing. Jul 2000;29(4):301-304.

Santos Palacios S, Pascual-Corrales E, Galofre JC. Management of subclinical hyperthyroidism. International journal of endocrinology and metabolism.Spring 2012;10(2):490-496.

Sanyal D, Raychaudhuri M. Hypothyroidism and obesity: An intriguing link. Indian journal of endocrinology and metabolism.Jul-Aug 2016;20(4):554-557.

Sapin R, Schlienger JL. [Thyroxine (T4) and tri-iodothyronine (T3) determinations: techniques and value in the assessment of thyroid function]. Ann Biol Clin (Paris).Jul-Aug 2003;61(4):411-420.

Schectman G, Byrd JC, Gruchow HW. The influence of smoking on vitamin C status in adults. American journal of public health. Feb 1989;79(2):158-162.

Schlesinger N. Dietary factors and hyperuricaemia. Current pharmaceutical design.2005;11(32):4133-4138.

Schreijer AJ, Reitsma PH, Cannegieter SC. High hematocrit as a risk factor for venous thrombosis. Cause or innocent bystander? Haematologica. Feb 2010;95(2):182-184.

Schulster M, Bernie AM, Ramasamy R. The role of estradiol in male reproductive function. Asian journal of andrology.May-Jun 2016;18(3):435-440.

Selva DM, Hammond GL. Thyroid hormones act indirectly to increase sex hormone-binding globulin production by liver via hepatocyte nuclear factor-4alpha. Journal of molecular endocrinology.Jul 2009;43(1):19-27.

Serin IS, Ozcelik B, Basbug M, Aygen E, Kula M, Erez R. Long-term effects of continuous oral and transdermal estrogen replacement therapy on sex hormone binding globulin and free testosterone levels. European journal of obstetrics, gynecology, and reproductive biology.Dec 1 2001;99(2):222-225.

Shaye K, Amir T, Shlomo S, Yechezkel S. Fasting glucose levels within the high normal range predict cardiovascular outcome. Am Heart J.Jul 2012;164(1):111-116.

Shen Q, Pierce JD. Supplementation of Coenzyme Q10 among Patients with Type 2 Diabetes Mellitus. Healthcare (Basel, Switzerland). May 21 2015;3(2):296-309.

Sherwani SI, Khan HA, Ekhzaimy A, Masood A, Sakharkar MK. Significance of HbA1c Test in Diagnosis and Prognosis of Diabetic Patients. Biomark Insights.2016;11:95-104.

Sherwin BB. Estrogen and cognitive functioning in women. Endocrine reviews.Apr 2003;24(2):133-151.

Shi X, Peng Y, Du X, Liu H, Klocker H, Lin Q, . . . Zhang J. Estradiol promotes epithelial-to-mesenchymal transition in human benign prostatic epithelial cells. Prostate.Oct 2017;77(14):1424-1437.

Shin JY, Lee HR, Lee DC. Increased arterial stiffness in healthy subjects with high-normal glucose levels and in subjects with pre-diabetes. Cardiovascular diabetology.Apr 15 2011;10:30.

Shlipak MG, Katz R, Sarnak MJ, Fried LF, Newman AB, Stehman-Breen C, . . . Siscovick DS. Cystatin C and prognosis for cardiovascular and kidney outcomes in elderly persons without chronic kidney disease. Annals of internal medicine.Aug 15 2006;145(4):237-246.

Simren M, Stotzer PO. Use and abuse of hydrogen breath tests. Gut. Mar 2006;55(3):297-303.

Smellie WS. When is "abnormal" abnormal? Dealing with the slightly out of range laboratory result. Journal of clinical pathology.Oct 2006;59(10):1005-1007.

Smith JL, Hodges RE. Serum levels of vitamin C in relation to dietary and supplemental intake of vitamin C in smokers and nonsmokers. Annals of the New York Academy of Sciences.1987;498:144-152.

Sorice A, Guerriero E, Capone F, Colonna G, Castello G, Costantini S. Ascorbic acid: its role in immune system and chronic inflammation diseases. Mini reviews in medicinal chemistry.May 2014;14(5):444-452.

Sp I, Ramona I, Sukesh. The efficiency of the serum prostate specific antigen levels in diagnosing prostatic enlargements. Journal of clinical and diagnostic research: JCDR.Jan 2013;7(1):82-84.

Stanworth RD, Jones TH. Testosterone for the aging male; current evidence and recommended practice. Clinical interventions in aging.2008;3(1):25-44.

Strain G, Zumoff B, Rosner W, Pi-Sunyer X. The relationship between serum levels of insulin and sex hormone-binding globulin in men: the effect of weight loss. The Journal of clinical endocrinology and metabolism.Oct 1994;79(4):1173-1176.

Strazzullo P, Leclercq C. Sodium. Adv Nutr. Mar 1 2014;5(2):188-90. doi:10.3945/an.113.005215.

Sudhir K, Komesaroff PA. Clinical review 110: Cardiovascular actions of estrogens in men. The Journal of clinical endocrinology and metabolism.Oct 1999;84(10):3411-3415.

Tinggi U. Selenium: its role as antioxidant in human health. Environmental health and preventive medicine.Mar 2008;13(2):102-108.

Toft AD, Beckett GJ. Thyroid function tests and hypothyroidism. BMJ (Clinical research ed.).Feb 8 2003;326(7384):295-296.

Tomita H. [Zinc-deficient disorders of sense organs--dark adaptation, taste and smell disorders]. Nihon rinsho. Japanese journal of clinical medicine.Jan 1996;54(1):141-147.

Urysiak-Czubatka I, Kmiec ML, Broniarczyk-Dyla G. Assessment of the usefulness of dihydrotestosterone in the diagnostics of patients with androgenetic alopecia. Postepy dermatologii i alergologii.Aug 2014;31(4):207-215.

Vandenput L, Ohlsson C. Estrogens as regulators of bone health in men. Nature reviews. Endocrinology.Aug 2009;5(8):437-443.

Velarde MC. Mitochondrial and sex steroid hormone crosstalk during aging. Longevity & healthspan.Feb 5 2014;3(1):2.

Ventura M, Melo M, Carrilho F. Selenium and Thyroid Disease: From Pathophysiology to Treatment. International journal of endocrinology.2017;2017:1297658.

Vermeulen A, Kaufman JM, Goemaere S, van Pottelberg I. Estradiol in elderly men. The aging male: the official journal of the International Society for the Study of the Aging Male.Jun 2002;5(2):98-102.

Veronese N, Watutantrige-Fernando S, Luchini C, Solmi M, Sartore G, Sergi G, . . . Stubbs B. Effect of magnesium supplementation on glucose metabolism in people with or at risk of diabetes: a systematic review and meta-analysis of double-blind randomized controlled trials. European journal of clinical nutrition. Dec 2016;70(12):1354-1359.

Vigil A, Condes E, Vigil L, Gallar P, Oliet A, Ortega O, . . . Jimenez J. Cystatin C as a predictor of mortality and cardiovascular events in a population with chronic kidney disease. International journal of nephrology.2014;2014:127943.

Volpe SL. Magnesium in disease prevention and overall health. Advances in nutrition (Bethesda, Md.).May 1 2013;4(3):378s-383s.

Watanabe R, Inoue D. [Current Topics on Vitamin D. Anti-cancer effects of vitamin D]. Clinical calcium. Mar 2015;25(3):373-380.

Whanger PD. Selenium in the treatment of heavy metal poisoning and chemical carcinogenesis. Journal of trace elements and electrolytes in health and disease. Dec 1992;6(4):209-221.

Wharton W, Gleason CE, Olson SR, Carlsson CM, Asthana S. Neurobiological Underpinnings of the Estrogen - Mood Relationship. Current psychiatry reviews.Aug 1 2012;8(3):247-256.

Whitley E, Ball J. Statistics review 2: samples and populations. Crit Care.Apr 2002;6(2):143-148.

Willinek WA, Ludwig M, Lennarz M, Holler T, Stumpe KO. High-normal serum homocysteine concentrations are associated with an increased risk of early atherosclerotic carotid artery wall lesions in healthy subjects. Journal of hypertension.Apr 2000;18(4):425-430.

Wise PM, Suzuki S, Brown CM. Estradiol: a hormone with diverse and contradictory neuroprotective actions. Dialogues in clinical neuroscience.2009;11(3):297-303.

Wojszel ZB. What Serum Sodium Concentration Is Suggestive for Underhydration in Geriatric Patients? Nutrients. Feb 15 2020;12(2)doi:10.3390/nu12020496.

Wood RI, Stanton SJ. Testosterone and sport: current perspectives. Hormones and behavior.Jan 2012;61(1):147-155.

Wright JL, Page ST, Lin DW, Stanford JL. Male pattern baldness and prostate cancer risk in a population-based case-control study. Cancer epidemiology.Apr 2010;34(2):131-135.

Wu BW, Berger M, Sum JC, Hatch GF, 3rd, Schroeder ET. Randomized control trial to evaluate the effects of acute testosterone administration in men on muscle mass, strength, and physical function following ACL reconstructive surgery: rationale, design, methods. BMC surgery.Dec 6 2014;14:102.

Yang X, Guo Y, He J, Zhang F, Sun X, Yang S, Dong H. Estrogen and estrogen receptors in the modulation of gastrointestinal epithelial secretion. Oncotarget.Nov 14 2017;8(57):97683-97692.

Yu JG, Bonnerud P, Eriksson A, Stal PS, Tegner Y, Malm C. Effects of long term supplementation of anabolic androgen steroids on human skeletal muscle. PloS one.2014;9(9):e105330.