Get Dr. Oz's complete vitamin guide for every age.
If you're a young, premenopausal woman, Dr. Oz says to look for a multivitamin that contains iron. "If you're menstruating, you'll need the iron to make new red blood cells," he says. "And you don't want more than 5,000 units of vitamin A."
If you're a postmenopausal woman or a man, Dr. Oz suggests a multivitamin without iron and no more than 2,500 units of vitamin A. "You don't need the iron, because you're not bleeding every month," he says.
Before you add this step to your daily routine, consult with your doctor. Dr. Oz says people who are taking medication to lower their cholesterol may need a different dosage.