context: Scientists don't know whether a daily multivitamin staves off disease, but many people take them to maintain or boost their health. Others take just one vitamin or mineral, like iron, to fill in a gap in their diets. Before you add a supplement or vitamin to your routine, go over these questions with your doctor, pharmacist, or registered dietitian: Can this supplement help me? Do I need it for a medical condition or to prevent disease? What does the research say about its benefits? How much would I take? When and for how long do I need it? Should I take it as a pill, powder, or liquid? Which form of the vitamin (vitamin D2 or D3, for instance) is the best? Are there any side effects? What are the best brands of this supplement in terms of quality, safety, and how well they work? Can I take it along with my other medications? Should I avoid any foods? Will I need to stop taking it if I have to have surgery? Vitamins and supplements come in many forms, like pills, liquids, or powders. The one you choose depends on how they work in your body and how you prefer to take them. For example, some only work in a dry extract form, such as a capsule or pill. Others work faster and are more effective as a liquid. Ask your pharmacist or doctor if you are confused about the right form to take. Certain supplements come in pills because they stop working, or become dangerous, if they come in contact with the acid in your stomach. Some people need to take a liquid if they have trouble absorbing vitamins from a pill, or even if it's hard for them to swallow capsules or tablets. And not all forms of a nutrient are the same. For example, vitamin D supplements come as either vitamin D2 or vitamin D3. Also, there are several types of vitamin E. When in doubt, talk with your doctor about which supplement suits your needs. Supplements are not regulated by the FDA in the same way that food and drugs are. The FDA does not review these supplements for safety or efficacy before they hit the market. The bottom line: Do your research and be careful when you're shopping for new products. Other ways to stay safe: If you eat a balanced diet rich in whole grains, fruits, and vegetables, you likely do not need to take a multivitamin. Talk to your doctor to see if you need any specific vitamins if you have a restricted diet. Although these nutrients are essential to our bodies, some can be harmful in high doses. It's especially important to avoid getting too much of vitamins A, D, E, and K, because these build up in your body and can become toxic. Supplements are not a good idea for people with some kinds of health conditions. They also can keep some medications from working as well as they should. Always talk with your doctor before you add any to your diet. People who should avoid certain types include: Pregnant or breastfeeding women, because some supplements can be dangerous to the baby. A daily prenatal vitamin has the right types and amounts of nutrients for these women. People who take heart medications, diuretics, blood thinners, aspirin, drugs that turn down the immune system, and steroids. With any type of drug, there's always a chance that it won't mix well with a supplement, but the problems can be especially severe with some of these drugs. People who are going to have surgery, because some products may lead to bleeding and other dangerous complications. People who've had cancer or are getting treated for it. Some supplements could help cancer cells grow or make treatments for the disease less effective. When you're ready to purchase supplements, keep these tips in mind: Look for evidence about how well the product works in scientific studies from credible publications. Search for such studies in the National Institutes of Health ( NIH) Pub Med database: www.ncbi.nlm.nih.gov/pubmed and the National Institute of Health - Office of Dietary Supplements. You can also call the manufacturer and ask what published studies they have to back up their claims. It's also a good idea to find out how they ensure the ingredients listed on the supplement label are actually in the bottle. If a product claims it will âcureâ a disease, is âall-natural,â or has a âmoney-back guarantee,â be on guard. Any supplement that sounds too good to be true likely is. Choose brands labeled with the NSF International, US Pharmacopeia, Underwriters Laboratory, or Consumer Lab seal. These verify that the product actually contains the ingredients that the label says it does, and that the product doesn't have any potentially harmful ingredients. Be wary of supplements made outside the United States. Many aren't regulated, and some may have toxic ingredients. Supplements don't last forever, and they need a little care to keep them working well. After you buy them: Keep them in a dark, cool, dry place. Avoid bathrooms and other damp spots. Make sure you keep them on a high shelf or in a locked cabinet, out of children's reach. Some vitamins and supplements wear out when they sit on the shelf for too long. Do a regular check of your stash and throw out any that are past their expiration date. Finally, always let your doctor know about any vitamins or supplements you plan to take, especially if you have a health condition or are on regular medication. Not all products work well for everyone, and some can be dangerous.