Q. Months ago I heard about the benefits of vitamin D. I ran an experiment on myself and found that a persistent pain in my back went away after I took 2800 IU of vitamin D three times.
Now a friend has sent an email message regarding the toxicity of vitamin D. I thought that this vitamin would be dangerous only at very high doses. Can you tell me, please, what amounts of vitamin D lead to toxic levels?
A. The RDA (recommended dietary allowance) for vitamin D is 600 IU for most adults (800 for those over 70). The tolerable upper limit is 4,000 IU daily. That is the amount that the government considers safe.
It is possible to overdose on vitamin D supplements, though you do have to take quite a lot. Doctors sometimes prescribe 50,000 IU of vitamin D to be taken once a week to correct deficiencies, and in most cases patients do not develop toxicity on that dose. Symptoms of trouble include digestive upset, confusion, weakness, irregular heart rhythms or kidney stones.
We are sending you our Guide to Vitamin D with tips on testing for deficiency plus the pros and cons about supplements. Safe doses and signs of toxicity are also discussed.
For more in-depth information on vitamin D, you may want to listen to our radio interview with Dr. Michael Holick and Dr. JoAnn E. Manson, the Vitamin D Debate. Both are leading experts on vitamin D, although they present quite different views on how much vitamin D is necessary.