The FDA doesn't test dietary supplements before they hit the shelves. Here's what you need to know.

If you take melatonin when you are struggling to get to sleep, vitamin D to help maintain healthy bones, or fish oil to help prevent heart disease, you are among over half of U.S. adults over the age of 20 who reported using dietary supplements, according to 2017-2018 data from the Centers for Disease Control and Prevention.

Multivitamins, which combine a range of vitamins your body needs and are intended to fill nutritional gaps, are the most common across age groups and are marketed to people in every stage of life. There are multivitamins for pregnant women, seniors who need extra immune health, and even gummy multivitamins for pill-adverse children and adults alike.

Unlike prescription drugs or over-the-counter medications, the shelves of dietary supplements you encounter in American grocery stores are largely untested by the Food and Drug Administration.

Northwell Health partnered with Stacker to break down how the FDA's regulation of dietary supplements differs from that of drugs and what consumers should look for to find safe and effective supplements.

Drugs vs. dietary supplements

Distinguishing between over-the-counter medications and dietary supplements can be tricky, especially since they often sit side-by-side on pharmacy shelves. The main differences, the FDA explains, are the marketing claims made about the product and the review process the product undergoes.

Drugs or medications are specifically formulated to cure or treat diseases and are "articles (other than food) intended to affect the structure or any function" of your body, according to the Federal Food, Drug and Cosmetic Act. Drugs undergo rigorous safety testing before the FDA lets them become available to the public.

Meanwhile, dietary supplements include ingredients in the food supply, like vitamins, minerals, and herbs. Following the Dietary Supplement Health and Education Act in 1994, dietary supplements were placed in a "special category under the general umbrella of 'foods,'" according to the FDA.

The marketing or packaging for a dietary supplement largely can't claim to treat a specific disease, but it can make statements about how its ingredients impact general well-being, like "fiber maintains bowel regularity," for example. There are, however, a few more nuanced rules regarding this when it comes to claiming to treat vitamin deficiencies.

However, the FDA does not review dietary supplements or their associated claims before they hit the market. In many cases, companies can legally begin selling supplements without even notifying the FDA.

Look for third-party testing

The FDA's approach leaves a void for American consumers worried about the ingredients or safety of their dietary supplements. Some nonprofit organizations and third-party companies have stepped up to provide some guidance.

The NSF, formerly called the National Sanitation Foundation, conducts its own product testing to ensure the ingredients in supplements match what the label lists and make sure there are no harmful levels of impurities. You can look for the NSF mark on dietary supplements and other products.

Similarly, products with United States Pharmacopeia approval undergo rigorous testing. USP professionals ensure the ingredients in the supplement break down in time to be absorbed in your body. You can search the USP database of approved products online.

Talk to a doctor first

Eating a variety of food is the best way to get nutrients. However, some people need dietary supplements to get extra vitamins that are missing from their diet.

Talk to your doctor before incorporating a new supplement. Taking supplements in addition to medication may cause serious side effects. Some supplements may change the effectiveness or how quickly a medication works.

Similarly, as you age, your body may need additional support. The National Institute on Aging encourages adults older than 50 to talk to their doctor about whether they need extra calcium, vitamin D, or vitamins B6 or B12.

Be wary of health fads

Social media users may be familiar with the health fads that come and go, and may be left wondering if supplements, which are often more affordable than drugs, can boost their health.

Does berberine, which comes from barberries among other plants, really help you lose weight as effectively as Ozempic? Will ashwagandha relieve anxiety? Will collagen strengthen your nails?

There is some research on the effectiveness of some dietary supplements, but experts generally recommend caution. If you are poking around the internet looking for answers, look for reputable sources like doctors or double-blind, peer-reviewed studies that included a lot of participants—and if at all possible, talk to a registered dietitian or health care provider before jumping on the bandwagon.

Story editing by Ashleigh Graf. Copy editing by Kristen Wegrzyn.