Click to View Are People Really Taking Sky-High Doses of Vitamin D?
Jul 11, 2017

By Perry Holman, Executive Director, Vitamin D Society

A new study1 recently reported trends in vitamin D supplementation in the USA from 1999 to 2014. It found that that vitamin D supplement use of ≥1000 IU or more per day increased from 0.3% in 1999 to 18.2% in 2014. Also vitamin D supplement use of ≥4000 IU per day increased from 0.2% in 2007 to 3.2% in 2014.

The researchers made this key point in their discussion:

“Overall, 3% of the population exceeded the tolerable upper limit of 4000 IU daily, and may be at risk of adverse effects as a consequence”

But how many people were really supplementing over 4000 IU/d? If they were just taking 4000 IU/d there would be no risk as this is the safe upper limit and does not require doctor supervision.

But the media based on the author’s statement reported the following sensational headlines:

Sky-High Doses: Taking Large Amounts of Vitamin D is on the Rise

More people than ever are taking way too much vitamin D

Taking Too Much Vitamin D Could Be Harmful To Your Health

High-dose vitamin D supplement use increasing, poses risk of adverse effects

But let’s examine the facts. How many people are exceeding the upper limit (UL) set by the Institute of Medicine2 (IOM) of 4000 IU/d and what is the real risk?

  • The study says 3.2% of people are taking ≥4000 IU/d. But the risk of adverse effects is only applicable to those taking more than 4000 IU/d. A dose of 4000 IU/d is perfectly ok. The authors fail to report the number of people taking more than 4000 IU/d in their research report. Suffice to say it would be below the 3.2% reported. Let’s put this in proper perspective. There would be substantially a far greater public health risk for all the people who do not have sufficient vitamin D blood levels and are at an increased risk for many serious diseases.


  • The Upper Limit (UL) of 4000 IU/d was set by the Institute of Medicine in 2010 but has not been accepted by vitamin D researchers and in fact has been aggressively challenged. The Endocrine Society3 also evaluated vitamin D and set their recommended UL at 10,000 IU/d. Plus the IOM2 determined that the No Observable Adverse Effects Limit (NOAEL) is 10,000 IU/d.


  • How much of a real health risk is this? Blood levels of 25(OH)D were not measured or reported in the study. So we do not know exactly if any of these people were near toxic blood levels. We do know that in research by Hathcock4 that vitamin D toxicity occurs after long-term doses of 30,000 IU/d or having a 25(OH)D blood level of over 500 nmol/L. 4000 IU/d is a long way under 30,000IU/d.

Keep in mind that making natural vitamin D from sunlight (UVB) exposure in the skin does not lead to vitamin D toxicity and is considered safe, as the body limits its own production. You can make between 10,000 – 25,000 IU of vitamin D per day from UV exposure.

But is 4000 IU/d actually a high dose for adults? Many vitamin D researchers believe that the IOM recommendations for adults are at least 10X too low and research papers have been published supporting this view5,6. Here is one example to illustrate this point:

The IOM recommends that infants receive 400 IU/d and adults 600 IU/d. So 400 IU for a 10 pound infant equals 40 IU/pound. Now 600 IU for a 200 pound man equals 3 IU/pound. Does it make sense to give an infant 40 IU/pound but only give adults 3 IU/pound? Will 3 IU/pound have any positive health effect at all on adults? This calculation shows that the IOM recommendation for adults is off by a factor of at least 10 when compared to the recommended infant dose. The adult dose should be 10X higher. If we use the 40 IU/pound level a 150 pound adult should be taking 6000 IU/d and a 200 pound adult should be taking 8000 IU. This level would be the same level or IU’s per pound as what the IOM recommends for an infant. If 400 IU for infants does not lead to “a risk of adverse effects as a consequence” than the same dose per pound should not lead to any risk for adults. This would invalidate the 4000 IU/d upper limit set by the IOM.

Dr. Robert Heaney reported “I am confident that this IOM error will be corrected sooner or later. This is partly because it is demonstrably erroneous, and partly because the related set of IOM recommendations for vitamin D has not elicited a consensus in the field of vitamin D research.”

I hope we have provided you with all the information and facts you need to make an informed decision as to whether people are taking sky high doses and way too much vitamin D!


  1. Rooney MR, Harnack L, Michos ED, Ogilvie RP, Sempos CT and Lutsey PL. Trends in Use of High-Dose Vitamin D Supplements Exceeding 1000 or 4000 International Units Daily, 1999-2014. JAMA. 2017;317(23):2448-2450. doi:10.1001/jama.2017.4392
  2.  Ross CR, Taylor CL, Yaktine AL, et al. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academies Press; 2011.
  3.  Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, Heaney RP, Murad MH, Weaver CM. Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab, 2011 Jul;96(7):1911-30. doi: 10.1210/jc.2011-0385
  4.  Hathcock JN, Shao A, Vieth R, Heaney R. Risk assessment for vitamin D. Am J Clin Nutr. 2007 Jan;85(1):6-18.
  5.  Veugelers PJ and Ekwaru JP. A Statistical Error in the Estimation of the Recommended Dietary Allowance for Vitamin D. Nutrients 2014, 6, 4472-4475; doi: 10.3390/nu6104472
  6.  Heaney R, Garland C, Baggerly C, French C and Gorham E. Letter to Veugelers, P.J. and Ekwaru, J.P., A Statistical Error in the Estimation of the Recommended Dietary Allowance for Vitamin D. Nutrients 2014, 6, 4472-4475; doi: 10.3390/nu6104472. Nutrients 2015, 7, 1688-1690; doi: 10.3390/nu7031688