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 100 mg/dL is considered normal by conventional medicine, levels above 85 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?”