PORTLAND, Ore., February 11, 2013 – Vitamin D supplement potency varies widely, and the amount of vitamin D in over-the counter and compounded supplements does not necessarily match the amount listed on the label, according to a research letter published in the journal JAMA Internal Medicine.
The analysis showed that the amount of vitamin D in these supplements ranged from 9 percent to 146 percent of the amount listed on the label. Not only was there variation among different brands and manufacturers, but also among different pills from the same bottle.