Dr. Arefa Cassoobhoy: Your doctor prescribed a drug for you to take, but you may have wondered whether a supplement would work just as well and be safer. There’s a lot of confusion about supplements, so let's take a look at how they compare to drugs. Let’s start with drugs. The FDA puts them through clinical trials to test them out. These tests have to show they are safe and will do what they are supposed to do. This all happens before your doctor can prescribe them. Now let's move to supplements. These herbs and vitamins are treated like food, so they don't have to be tested. They are self-regulated by the manufacturer, instead of the FDA, so the people who make the supplements are in charge of monitoring them. In fact, the FDA only steps in if they have caused a health problem. So overall, drugs are considered unsafe until they are shown to be safe. Supplements are considered safe until they are shown to be unsafe. Be aware that drugs and supplements can interact with each other and impact your health. Most supplements are ok. But there have been some problems. In one study, half of the herbal supplements tested didn’t even contain the ingredient listed on the label! If you’re planning on taking a supplement, you’ll need to do some research on your own ahead of time. Some supplements have an important role in a healthy lifestyle, like taking folic acid if you’re pregnant. So talk to your doctor about making the best choice. For WebMD, I’m Dr. Arefa Cassoobhoy.