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Dear Dr. Roach: Several years ago, in my early 80s, my gynecologist told me (like all women who mainly stayed indoors) that I should be taking 4,000 IU of vitamin D3 daily. Yet today, I read an article warning that many people are overdosing on vitamin D. Is this really a concern? -- L.M.
Answer: Overdosing on vitamin D is dangerous. Last month, I had a patient who had elevated levels of calcium, which caused typical symptoms of confusion, vomiting and muscle weakness. She was found to have a very high blood vitamin D level. (She had mistaken the instructions for taking vitamin D.)
I have also seen vitamin D toxicity in people who are prescribed 50,000 units once a week for a month and mistakenly take this each day. (I don't prescribe this formulation as I have seen mistakes like this too often.) Toxicity is almost unheard of at 4,000 units daily. Up to 5,000 or even 8,000 units of vitamin D3 daily are very unlikely to cause excess.
Screening and treatment for vitamin D deficiency is less often done since the publication of a large study that showed few benefits to treatment. However, it is still appropriate to consider vitamin D deficiency in some high-risk groups.
This includes older adults who don't go outside much but also people who don't absorb calcium well (especially those with a history of bariatric surgery, inflammatory bowel disease, or celiac disease). It can also occur in dark-skinned people or those who wear sun-protective clothing all the time.
Some medicines (especially for epilepsy) can increase the body's metabolism of vitamin D. I recommend obtaining your blood levels prior to starting vitamin D supplementation to confirm that the level is optimal during therapy.
Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu.