In a new review, researchers examined data from 21 clinical trials with dosages of vitamin D ranging from 10 mcg per day to 2,500 mcg per day and found no adverse effects up to 1,250 mcg per day. Doctors noted that nearly all prior negative reports for vitamin D (toxicity) involved doses above 2,500 mcg (100,000 IU) per day.
The body makes vitamin D from sunlight, but most people living in less sunny northern climates may be deficient. There are small amounts of vitamin D in milk, fish and liver that typically account for about 2.5 mcg per day.