Vitamin D by Dr. Mercola

Vitamin D

By Dr. Mercola

I believe there are compelling reasons to really make a concerted effort to get ALL your vitamin D requirements from exposure to sunshine or by using a safe tanning bed.

However, if neither of these are feasible options, then you should take an oral vitamin D3 supplement.

Before considering supplementation with vitamin D, it would be wise to have your vitamin D level tested, and regardless of the method you use, it’s important to measure your levels from time to time to make sure you’re maintaining therapeutic levels year-round.

This is best done by a nutritionally oriented physician, as it is very important that they order the correct test.

The advantage of having your medical doctor perform the test is that it will usually be covered by your medical insurance.

Don't Be Fooled -- Order the Correct Test

There are two vitamin D tests -- 1,25(OH)D and 25(OH)D.

The correct test is 25(OH)D, also called 25-hydroxyvitamin D. This is the better marker of overall D status, and is most strongly associated with overall health.




Deficient                         Optimal                   Treat Cancer and Heart Disease                  Excess

                                < 50 ng/ml                   50-70 ng/ml                             70-100 ng/ml                              >100 ng/ml

Multiply ng/ml by 2.5 to convert to nmol/litre



Please note the difference between normal and optimal. You don't want to be average here; you want to be optimally healthy. Primitive man likely developed in tropical and sub-tropical conditions with large exposure to UV-B and its secondary consequence to skin exposure, vitamin D. Primitive environmental availability of a nutrient does not necessarily establish the higher requirements, but these exposures would have influenced the evolution of the relevant physiology, and such concentrations should at least be considered presumptively acceptable.

Some experts may disagree with the following ranges, but they are taken from healthy people in tropical or subtropical parts of the world, where they are receiving healthy sun exposures. It seems more than reasonable to assume that these values are in fact reflective of an optimal human requirement.

Holick MF. Calcium and Vitamin D. Diagnostics and Therapeutics. Clin Lab Med. 2000 Sep;20(3):569-90)


If you have the above test performed, please recognize that many commercial labs are using the older, dated reference ranges. The above values are the most recent ones based on large-scale clinical research findings.

Make Sure Your Lab Uses the Correct Assay

There are a number of different companies that have FDA approval to perform vitamin D testing, but the gold standard is DiaSorin Their radioimmunoassay (RIA) method for measuring total vitamin D levels has become the gold standard, not because it's more accurate than the others, but because it's the one used in almost every major vitamin D study, on which the recommended blood levels for clinical efficacy are based.

If you’re in the United States, it is my strong recommendation to use tests that are either from Lab Corp, or the blood spot test that uses, which you can do via mail.

Dosing Recommendations for Oral Vitamin D

There is no one-size-fits-all dosage level at which "magic" happens, but based on the most recent research by Grassrootshealth—an organization that has greatly contributed to the current knowledge on vitamin D through their D Action Studyit appears as though most adults need about 8,000 IU's of vitamin D a day in order to get their serum levels above 40 ng/ml. This is significantly higher than previous vitamin D recommendations!

For children, many experts agree they need about 35 IU's of vitamin D per pound of body weight.

At the time GrassrootsHealth performed the studies that resulted in this increased dosage recommendation, the optimal serum level was believed to be between 40 and 60 nanograms per milliliter (ng/ml). Since then, the optimal vitamin D level has been raised to 50-70 ng/ml, and when treating cancer or heart disease, as high as 70-100 ng/ml, as illustrated in the chart above.

What this means is that even if you do not regularly monitor your vitamin D levels (which you should), your risk of overdosing is going to be fairly slim, even if you take as much as 8,000 IU's a day. However, the only way to determine your optimal dose is to get your blood tested regularly, and adjust your dosage to maintain that optimal range.

Remember, unless you get a deep dark tan, which is a pretty good indicator that your vitamin D3 levels are where they need to be, it is wise to get your blood levels checked -- that is the only way to know for certain you have reached therapeutic levels.

Supplement with the Correct Vitamin D

There are two types of vitamin D supplements: vitamin D3 (cholecalciferol), which comes from fish oil, and plant source D2 (ergocalciferol), which is found in fortified foods and some supplements. D2, found in plants and made active by irradiation, is less biologically active.

Vitamin D3 is found in eggs, organ meats, animal fat, cod liver oil, and fish. It is equivalent to the vitamin D3 formed on your skin from UV-B. You should stay away from the synthetic D2 as it has been shown to be toxic at the higher dose ranges.

You will only want to use vitamin D3 (cholecalciferol).

A meta-analysis by the Cochrane Database1, which looked at mortality rates for people who supplemented their diets with D2 versus those who did so with D3, highlights the importance of using the correct type. The analysis, which included 50 randomized controlled trials (a total of 94,000 participants), found:

  • A six percent relative risk reduction among those who used vitamin D3, but
  • A two percent relative risk increase among those who used D2

There are additional reasons why vitamin D2 has a greater potential for harm. First, vitamin D binding protein has a weaker affinity for the vitamin D2 metabolites than vitamin D3. Second, unique, biologically active metabolites are produced in your body from vitamin D2, but there are no analogous metabolites derived from vitamin D3. There is no doubt that vitamin D2 is a synthetic analogue of vitamin D, with different characteristics. But it is inappropriate to regard vitamin D2 as a vitamin. Future research into the toxicity of vitamin D needs to focus on vitamin D3 as being something distinct from vitamin D2, for which almost all our current toxicity data relate to.

People Who Should Avoid Vitamin D

If you have sarcoidosis, tuberculosis, or lymphoma, it would be best for you to avoid oral vitamin D supplementation based on this test. It is recommended that you perform the 1,25(OH)D test before you supplement with any sun exposure or oral vitamin D, as it is a better indicator in people with this health challenge.

By Dr. Mercola

A robust and growing body of research clearly shows that vitamin D is absolutely critical for good health and disease prevention.

Vitamin D affects your DNA through vitamin D receptors (VDRs), which bind to specific locations of the human genome. Scientists have identified nearly 3,000 genes that are influenced by vitamin D levels, and vitamin D receptors have been found throughout the human body.

Is it any wonder then that no matter what disease or condition is investigated, vitamin D appears to play a crucial role?

This is why I am so excited about the D*Action Project by GrassrootsHealth.1 It is showing how we can take action today on known science with a consensus of experts without waiting for institutional lethargy.

It has shown how by combining the science of measurement (of vitamin D levels) with the personal choice of taking action and, the value of education about individual measures that one can truly be in charge of their own health. In order to spread this health movement to more communities, the project needs your involvement, your health activism. This is an ongoing campaign during the month of February, and will become an annual event.

Tens of Thousands of Studies Attest to Vitamin D’s Health Impact

According to a January 17 press release by Orthomolecular Medicine,2 3,600 medical papers with vitamin D in the title or abstract were published in 2012 alone, bringing the grand total to 33,800. That’s a lot of studies on vitamin D. The Top 16 vitamin D papers of 2012 selected by a panel of vitamin D experts focused on vitamin D’s beneficial impact on:

Pregnancy outcomes (reduced risk of Cesarean section and pre-eclampsia)


Childhood language impairment

Cardiovascular disease

Type 1 diabetes

Type 2 diabetes

Bacterial and viral infections


Falls and bone fractures

All-cause mortality

If You Take Vitamin D Supplements, Remember to Take Vitamin K2