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.

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  1. Kathie D.

    My doctor prescribed 50,000 IU/once a week, which I faithfully took for several weeks. I began to notice dizziness, chest pains, severe headaches, and what I can only describe as an oily taste in my mouth. The only thing I had done differently was the Vitamin D.
    Only after stopping the once a week dose did the symptoms subside. I am quite angry about this. I felt bad enough that I was wondering if I needed to go to the emergency room. My system could not tolerate that massive dose- I doubt I’m the only one.
    Once my system clears I will take a much smaller dose with my regular supplements.

  2. lcf

    Or, you could sit in the sun for 15 minutes and get the real stuff! I have read that only 15 minutes a day will supply the body with all the vitamin D necessary to maintain good health. Since I live in Florida, that is pretty easy to do. Just don’t overdo it.

  3. Dan St.

    Optimal levels of vitamin D are about 50-90ng/mL. Almost everyone needs more than about 3000 or 4000 units to achieve these blood levels. The official recommendations from the government and medical establishment regarding vitamin D are bunk and are contradicted by the science. Vitamin D is highly effective, which means it is a threat to the dishonest and disgusting business model of the medical establishment: promoting chronic illness.

  4. RDW

    I am surrounded by lots of people whose doctors have said they are deficient in Vitamin D. My cal/mag supplement has 400 units of vitamin D3. At one point I decided to take extra D3 to see how I reacted. Increasing the D3 caused the muscles in my lower leg near my ankle to twitch. When I went off the the extra D3 the twitching went away, so I have concluded that I do not need extra vitamin D. I have also read where a lot of the prescription D is D2. It is my understanding that D3 is closer to what the body makes than the D2. The mega dosage vitamin D hype is so new I don’t think anyone yet knows how people are going to react to this in the long run. We all are test subjects in whatever we take – prescription wise and supplement wise.

  5. ck

    Viatamin supplements as well as OTC’s are to be taken under the supervision of a professional ie MD. I was diagnosed with such deficiency of Vitamin D that my doctor put me through a plethora of tests thinking I have cancer of the parathyroids. Fortunately all tests were negative and after years of high doses – the green capsules are sold by Rx only – I am now on 1000 IUs daily and feeling great.

  6. Karen

    This information does not distinguish between D2, which is easy to overdose on, and D3 which is much harder on. Blood tests can tell whether the blood level is approaching overdose.

  7. Laura

    The answer is simple: just have a blood test to measure your vitamin D levels. I’ve been taking 5,000 IU daily for about 4 years. My level is finally near normal (about 70) after having been as low as 19. BTW, I haven’t had a cold — not one — since!

  8. HN

    According to a study that was published in the American Journal of Clinical Nutrition in January, 2007 (John N Hathcock, et. al.), vitamin D toxicity could only be found at doses above 30,000 IU/day and at serum 25(OH)D levels above 200 ng/mL. That study looked at multiple clinical trials and case studies in an attempt to find evidence that would support the Food and Nutrition Board’s Upper Limit recommendation (at that time) of 2,000 IU/day. Instead, the study found that their recommended UL was “not based on current evidence and is viewed by many as being too restrictive, thus curtailing research, commercial development, and optimization of nutritional policy.”
    There have been thousands of studies on vitamin D since that study six years ago, but the UL recommendation has only been raised to 4,000 IU/day, so it is still lagging the research and preventing people from reaching OPTIMAL levels of vitamin D. In my personal opinion, that level is probably between 70 ng/mL and 100 ng/mL, but it could take a few more years before we see recommendations for that level.

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