Research shows that adults taking more than 10,000 IU of vitamin D daily who ... these symptoms occurred in response to extremely high doses of vitamin D3, which led to calcium levels greater ...

A 21-year-old man or women exposed to summer UVB light generates 10,000 IU (the equivalent of 250 mcg, 25 multivitamin pills of vitamin D, or 100 glasses of milk) of vitamin D in 15 to 20 minutes.