25 OH Vitamin D Test

In a previous blog, Vitamin D Sources, Benefits, & Toxicity, we answered the first question often asked during our nutrition seminars, “What does vitamin D do?” In this blog, we’re responding to the second question: “How do I know whether I have enough vitamin D?”

Well, if you’ve been avoiding the sun and not taking vitamin D3 supplements, you’re likely deficient in vitamin D—and setting yourself up for a lot of unexplained pain and a whole range of nasty diseases. (See our previous blog Vitamin D: Sources, Benefits, and Toxicity.)

Vitamin D Deficiency

We refer to Vitamin D Deficiency as VDD (our personal shorthand for the most significant nutritional deficiency in North America, and likely a lot of other places).

A simple blood test called a 25 OH Vitamin D Test will reveal if you are VDD.

However, before rushing off to your doctor to insist (yes, insist) on the 25 OH Vitamin D Test, you can administer a quick self-check. Consider that your body works with sunlight to produce vitamin D, then ask yourself, “Am I exposing large areas of bare skin (arms, legs, back) to sunlight 15-20 minutes a day, without sunblock?”

If the answer is no and you follow a typical North American diet and lifestyle, there’s a good chance you’re VDD.

In any case, get the test to be sure.

Interpreting the 25 OH Vitamin D Test

The 25-hydroxyvitamin D test is administered through a blood sample and reported as “nanograms per milliliter” (ng/ml) in the U.S.A. and as “nanomolecules per liter” (nmol/L) in Canada.

50-80 ng/ml or 125-200 nmol/L are considered good levels. Be aware, however, there is ongoing debate about levels.

Some guidelines recommend “minimum” or “normal” levels (20- 56 ng/ml or 50-140 nmol/L), but don’t consider them your target. Here’s why: You want enough vitamin D in your body for immediate use and for storage against the day when you just can’t synthesize any vitamin D.

Consider, too, that your body’s fat and muscle tissues won’t even begin storing vitamin D until you have 40-50 ng/ml. That’s one clear indication your body wants the stuff available all the time, every day, every month, all year long—get it? Use this information to discuss optimum levels for you with your doctor.

What to do? Have a look at our previous blog to refresh yourself on vitamin D’s importance, get the test, and discuss the results with your doctor. Just don’t take vitamin D for granted.

You can reach Gloria Askew, RRN, and Jerre, Ph.D at

You can read more about Gloria and Jerre’s book, Secrets of Supplements: The Good, the Bad, the Totally Terrific, here.

You can also read our blogs at


Search Posts

Eat to Save Your Life BookEat to Save Your Life answers the hard nutrition questions.

Buy it now!