Read an article in some grocery store magazine about vitamin D assisting in weight loss.

D is absorbed into fat, but people taking amounts in excess of that can lose weight.

They cited some tests to determine the right amount at your doctor but also a simple formula: 25 X weight.

So if I am 250 lbs, then 25 X 250 = 6250 iu daily. One would have to take far more than this to "overdose".