Effects of Vitamin D Overdose A British man's vitamin D overdose is a warning to people considering adding vitamin supplements to their lives, according to an article published Tuesday in the journal BMJ Case Reports. After a visit to a private nutritionist, the man began taking more than 20 over-the-counter supplements every day, including 50,000 international units (IU) of vitamin D three times a day. That's a dose hundreds of times higher than standard nutritional recommendations. Within a month, the man began to experience nausea, abdominal pain, diarrhea and repeated bouts of vomiting, as well as leg cramps and ringing in his ears. The man, whose name was not released, learned about the supplements on a radio talk show and then contacted the show's nutritionist, said Dr. Alamin Alkundi, a co-author of the report and an endocrinologist at William Harvey Hospital in East Kent. in the UK, who treated the man. "Regulatory registration is not co...