25 October 2009

Which Vitamin D Test to Get? 25-hydroxy-vitamin D!

Swine flu and seasonal flu are in the air. We're close to panic season now. At work, more than 1500 people showed up in one day to get flu shots. They had to turn people away.

Some of my family members recently had flu-like symptoms for several days, then recovered. A family doctor said it was in all likelihood the swine flu. I didn't get (some really minor feverishness, followed by a nap and all was ok).

There is evidence that sufficient blood levels of Vitamin D is protective against colds, flu, and even cancer. Read about Vitamin D here. Also Grassroots Health is an excellent resource.

When I went to my doctor in the spring, he ordered a vitamin D test, but it was not the "right" one, so I had him change it.

For the record, you should get a 25-hydroxy-vitamin d test, and the results should be 50–80 nanograms per milliliter (ng/mL) or 125–200 nanomoles per liter (nM/l) year-round.

If you are below that range, consider supplementation with Vitamin D3 (cholecalciferol), not D2 (ergocalciferol). It makes a difference, although there is some controversy. Some claim that oil based caplets offer more reliable absorption than dry pills.

Many people like the Carlson Gelcaps.

I use Costco myself.

An excellent overall resource to learn about Vitamin D is the Vitamin D Council.

If you have trouble with your doctor, you can get a mail-order vitamin d test.

While you're at it, you might consider Vitamin K2 levels as well...

What Blood Test Should I Have?
from an article by John Cannell

"The only blood test that can determine vitamin D adequacy is a 25-hydroxy-vitamin D. Whenever I say "vitamin D level," I'm talking about a 25-hydroxy-vitamin D. Ask your doctor to order a 25-hydroxy-vitamin D blood test. Unfortunately, many doctors order an "activated vitamin D" level, thinking it better to measure the most active form of vitamin D. It is not. Activated vitamin D, also known as 1,25-di-hydroxy-vitamin D or calcitriol, should never be obtained to determine vitamin D sufficiency. Calcitriol is often elevated in vitamin D deficiency. You cannot tell anything about your vitamin D nutrition by measuring a calcitriol level. If your doctor insists on ordering a calcitriol level to determine your vitamin D nutrition, find another doctor."

"(Although 1,25 dihydroxy-vitamin D (calcitriol) should never be used to diagnose vitamin D deficiency, calcitriol is important in evaluating one cause of high blood calcium, called vitamin D hypersensitivity. High blood calcium rarely occurs due to vitamin D toxicity, but calcium is elevated in people who have vitamin D hypersensitivity, although their vitamin D level will be normal or even low. Primary hyperparathyroidism is a common cause of vitamin D hypersensitivity, as is sarcoidosis and other granulomatous diseases. It can occasionally occur in cancer; about 20% of patients with non-Hodgkin's lymphoma have vitamin D hypersensitivity. Any competent endocrinologist can treat vitamin D hypersensitivity.)"

"However, serious problems exist with the technology used by some laboratories to measure vitamin D levels. Different labs will report different results when given the exact same specimen of blood. Furthermore, the same lab often reports significantly different numbers when sent the same specimen of blood at different times. In general, low numbers are more reliable than high numbers because interfering substances can easily give falsely elevated results. Prominent scientists have issued urgent calls for standardization. ...

"If you take ergocalciferol, or "vegetarian" vitamin D, be warned. Ergocalciferol is not vitamin D, but a vitamin D-like patent drug whose patent has expired. It does not normally occur in the human body and is probably a weak agonist at the receptor site, meaning it may actually partially block vitamin D actions. Ergocalciferol is the villain in most of the reported cases of toxicity in the world's literature. All bets are off in terms of measuring blood levels if you take ergocalciferol. Some of the labs can pick it up, and some can't. Don't take ergocalciferol; it is not vitamin D."


  1. i find it torturous that we need to fact-check doctors.

    this seems like good information to me.

  2. It's really sad that we need to make sure our doctors are getting it right.

    At the same time, one of the reasons I did this post is that my wife's doctor ordered a vitamin D test for her (the right one).

    Things move slowly, but they do move.

    Thanks for your comments.


  3. I am a dietitian and interpret labs for patients every day. I also find that many MD's do not fully understand the labs and because of either ego or time constraints do not take the time to learn.