What to Expect from a Vitamin D Test

by Melissa Chichester

Vitamin D is a fat-soluble vitamin that supports strong bones and teeth by helping them absorb calcium.*

Vitamin D also helps maintain a healthy immune system.* Although it is one of the most important vitamins for good health, it is also one of the most challenging to get for some people. 

Vitamin D is received when your skin is exposed to sunlight. You can also receive it through certain foods, such as mushrooms. Unfortunately, as many as 96% of Americans do not get enough vitamin D from food alone.

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Certain populations are more prone to Vitamin D deficiency, such as adults over 65, African Americans, and people who live above 37 degrees latitude. In the United States, that is approximately north of Oklahoma and Southern Illinois. In Europe, it’s north of the Mediterranean Sea.

One of the best ways to determine if you have a deficiency is to request a Vitamin D test from your physician. It’s simpler than you think, and here’s how it works. 

Taking a Vitamin D test

In the bloodstream, Vitamin D turns into a form called “25 hydroxyvitamin D” (also known as 25(OH)D). This can be measured with a simple blood test. A health care professional will use a small needle to take a sample of blood, just like any other blood tests you may have had. And unlike some tests, you do not have to do anything to prepare. You do not have to fast for a Vitamin D test unless you are having other tests done at the same time that require it. 

Vitamin D test results 

Your test results may reveal important information about your Vitamin D levels. Ideal Vitamin D levels are 20 nanograms/milliliter to 50 ng/mL. The results will inform you if your levels are too low, just right, or too high.

A lower test result may indicate that you are not receiving enough sunlight, not eating Vitamin D-rich foods, or you may have trouble absorbing fats.

Your physician will make recommendations based on your test results. That may include Vitamin D supplements, more ways to get sunlight, or even other tests to make sure you are absorbing fats properly. 

According to The Endocrine Society, Vitamin D deficiency is very common and as a result, testing is recommended if you suspect you are deficient. You may also want a Vitamin D test for peace of mind. If you think this test is right for you, speak with your physician about your testing questions. 

  1. Dickinson., A., MacKay, D. Nutr. J. 2014, 13:14.