If you’re vitamin D-deficient, taking a vitamin D3 supplement could offer potential benefits, experts say. But how often do you actually need to take it, and who should avoid it? Vitamin D is a ...

Our bodies make vitamin D3, cholecalciferol. At the supplement counter, you can choose from D3 or D2. Vitamin D2 is ergocalciferol, which differs slightly from D3 but behaves the same way in the body.