Don't Overdo It
Although it's tempting to take higher doses of supplements, in some cases too much can harm your health. Extra selenium, for example, can make your nails brittle and your hair fall out. Too much vitamin A may increase the risk of hip fracture or some birth defects. And although its precursor, beta-carotene, is generally considered safer, there is reason to approach it, too, with some caution, says Dr. Brent Bauer. "At high doses, it led to increased cases of cancer in smokers." If you're taking a blood thinner, check with your doctor before taking a multivitamin that contains any vitamin K.

Do Keep Food-and-Drink Tips in Mind
-Taking most supplements with food can help you avoid an upset stomach -- but it can also impact their effectiveness.

- Take calcium supplements in two dosages for proper absorption. Your best bet? Pair them with breakfast (and later, dinner) -- unless you're having high-bran cereal. Phytates, found in wheat bran, can inhibit the absorption of calcium, according to the National Osteoporosis Foundation. The good news: Bran only affects absorption at that meal, so you can safely take your supplement a few hours later.

- If your doctor has advised you to take iron supplements for anemia, avoid taking them with coffee or tea because the tannins can block the absorption. Instead, have them with a glass of orange juice, as the vitamin C will boost iron's absorption.

- If you're taking your supplements with dinner, avoid drinking alcohol, which can compromise absorption of certain vitamins and minerals.

Do Watch the Clock
In general, the best time to take your supplements is whenever you'll remember, as regularity is key to getting the most benefit from them. One exception: B vitamins work on neurotransmitters and can have an energizing effect, so avoid taking them at bedtime.