If you re in one of these groups, it may be wise to look for a pill with less than 9 milligrams of iron. It helps absorb calcium and many older people have vitamin D deficiencies. This vitamin can help the immune system and may lower homocysteine, a risk factor for heart attacks. A multivitamin with at least 2 milligrams is often a good idea. But avoid excess doses.
Vitamins can affect some medications and health conditions.