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What does “normal” really mean when it comes to lab tests?

March 23, 2017

Naturopathic and functional medicine practitioners often interpret conventional labs more carefully than just a binary determination of “normal/abnoral”. There is good reason for this. A more careful look at lab values can an ammount to a life preserver for medical refugees who are castaways from strict interpretations.

Shoe size is a good analogy regarding lab interpretation. Most labs define “normal” as the average result of a pool of asymptomatic patients plus or minus 2 standard deviations. This covers about 90% of the “normal” population. If you were to use this standard to determine what the average shoe size was, it would probably be somewhere between 6 and 12. Given biological individuality, it becomes rather absurd to suggest that you could give any human being a shoe between size 6 and 12 and expect it to fit. In this way, conventional laboratory ranges can be seen as useful when determining if someone in a broad population selection is clearly experiencing a physiologic problem. However, when we have an individual in front of us with symptomology to consider, it pays to identify where that person falls within the conventional laboratory ranges.

Lab normal ranges
One example is thyroid stimulating hormone (TSH). Most conventional labs suggest that anything from 0.5 to 5.0 mIU/L is normal. However, there is substantial evidence from conventional governing bodies for over a decade to the contrary. The National Academy of Clinical Biochemistry recommended that the upper limit of TSH should be 3.0, while the American Association of Clinical Endocrinologists set the upper limit at 2.5. Other qualified advisory groups went as low as 2.0 for the upper limit of the optimal range in symptomatic patients.

The goal in complementary medicine is to help patients that are left stranded by a strict  interpretation of their lab results from an outdated conventional reference range. I call these patients “medical refugees”. One of the key missions in functional medicine is to identify and help these patients.

Another example is C-reactive protein (CRP) a marker of inflammation. Normal might be anything between 0.1 and 3.0. However, when I have a patient who is suffering from inflammatory symptoms or conditions of any kind, I like to see the CRP below 1.0, and I am likely to take measures to help decrease inflammation in these patients.

If I have a patient suffering from fatigue who is in the bottom 10% of the normal range for ferritin or serum iron, and they look pale, I’m not going to tell them that their iron levels are fine. I’m going to suggest that they take additional iron.

Whatever I am going through labs with the patient, I always look at where their valuesa are within the normal range–at least for the labs that could relate to their symptomology. It takes more time to do this, but the effort frequently pays off for the medical refugees who may have been neglected by a strict conventional medical interpretation of their lab values.

If you would like to have a “functional” interpretation of your labs, I look forward to working with you to promote your optimal health.

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