The ZRT Laboratory Blog

The ZRT Blog is an extensive resource for patients and health care providers searching for health and hormone testing information. Here, you can read about ZRT’s cutting edge research, advances in testing, wellness advice, and health industry highlights.

Posted by Jillian Harrington, PhD, HCLD on Wednesday, 10 January 2018

Vitamin D: What Level is Normal vs Optimal? 

Woman shading her face from the sun

If you have ever had your level of Vitamin D tested, depending on which lab you used, your report showing whether your level is low, normal, or high might have left you scratching your head. In fact, there are multiple agencies all with slightly different opinions on what levels are deficient, insufficient, sufficient, high, or toxic.

When testing with ZRT, you will receive a result that is reflective of your total 25-Hydroxy Vitamin D status (vitamin D2 plus Vitamin D3) in blood. This is the storage form of vitamin D, which is converted by the kidneys to the biologically active form, 1,25-dihydroxycholecalciferol.

Vitamin D3 is involved in numerous biological processes such as immune system modulation, insulin sensitivity, hormone and neurotransmitter homeostasis, and is essential for ensuring calcium absorption in the bones. Dietary sources of vitamin D include foods such as cow’s milk, fish, egg yolk, and pork. Sunlight exposure and supplements are two other main sources of vitamin D that will contribute to reaching an optimal vitamin D status for health. Those of you who are not living in a sunny climate year-round will be hard-pressed to maintain a healthy level of vitamin D by relying on sunlight alone.

Reference Range

The reference range, a term often used in conjunction with laboratory testing, is a set of values that include the upper and lower limits of a lab test based on a group of otherwise healthy individuals. For a laboratory to determine the appropriate reference range for their testing population, often hundreds to thousands of normal, healthy patients are tested. To date, ZRT has tested over 60,000 patients to assess their vitamin D levels. When looking at the patient results, we determined that the majority of patients tested have total vitamin D levels between 20 and 80 ng/mL; that is, 86% of patients tested fall within this range. Based on years of patient testing and data analysis, we have updated our laboratory report reference range to reflect that values between 20-80 ng/mL are representative of a normal patient population.

Normal versus Optimal

Based on years of patient testing and data analysis, we have updated our laboratory report reference range to reflect that values between 20-80 ng/mL are representative of a normal patient population.

This raises the issue: is normal the same thing as optimal? Not necessarily. The Vitamin D Council places the ideal level between 40 and 80 ng/mL with levels below 20 ng/mL as deficient. The Endocrine Society has a Clinical Practice Guideline on the evaluation, treatment, and prevention of vitamin D deficiency. This guideline recommends a minimum vitamin D level of 20 ng/mL, but to guarantee sufficiency they recommend between 30 and 50 ng/mL for both children and adults. In contrast, the Vitamin D Council states that even levels between 30 and 40 ng/mL are still not quite sufficient. On the other end of the spectrum, results that fall between 80 and 100 ng/mL are not achievable naturally; that is, they are only reached with some form of vitamin D supplementation. So, while they are not harmful levels, they are instead reflective of supplementation and therefore not what would be detected in a "normal" patient population. 

So, what does it mean if your test result falls within ZRT’s updated reference range of 20 to 80 ng/mL? It means that your result is normal within the testing population, but if you are at the lower end of the range it may not be sufficient for optimal vitamin D status. According to most standards, sufficient values for vitamin D are between 30 and 60 ng/mL. For those with chronic conditions like diabetes, autoimmune disease, or cancer, it’s not unusual for a provider to target a vitamin D level higher than the typical sufficient range. Whatever your number and health status, work with your provider to achieve the optimal level for you, through supplementation, nutrition, or getting more sun exposure. Your choice! When in doubt, give our ZRT Clinical Consultants a call and they can help walk you through the ever-evolving and sometimes conflicting data regarding ideal vitamin D levels. 

For more information on how ZRT determines reference ranges, see http://blog.zrtlab.com/reference-ranges

Download ZRT's Blood Spot reference range document that includes updated Vitamin D reference ranges. 

 

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