How to Choose a Quality Supplement: Third-Party Testing, Labels and FDA Warnings

In the US, a supplement can go on sale without the FDA checking first that it is safe, that it works, or that the label is right (FDA). The company is responsible for that. So the bottle in your hand may hold more, less or something other than its label says. Here is what lab studies have found, what a third-party seal does and doesn't tell you, and how to check a product yourself in a few minutes. On this page, grades rate how consistent the testing and surveillance data are, not trial evidence (how we grade).

The short version

• Labels often miss. More than 71% of 31 melatonin products were off their label by more than 10%, and 36 of 44 weight-loss products bought on or near US military bases had inaccurate labels. B Grade B (Erland 2017; Crawford 2024).
• Hidden prescription drugs cluster in three kinds of product: sexual enhancement, weight loss and muscle building. B Grade B (Tucker 2018; White 2022).
• Sports supplements can contain banned substances. Studies have found them in 14% to 50% of samples tested. B Grade B (Jagim 2023).
• A third-party seal means an outside lab checked that product, but each programme tests different things. C Grade C (Eichner 2019).
• Check it yourself: confirm the seal on the programme's own website, search the FDA's tainted-products database, and report problems to the FDA.

Are supplements approved by the FDA?

No. The FDA has no authority to approve supplements, or their labels, for safety and effectiveness before they are sold. Companies are responsible for making sure their products meet the law, and because many products can reach shelves without the FDA being told, the agency mostly acts after a product is on the market (FDA). That is why "FDA approved" on a supplement is a red flag, and why independent testing matters.

How often are supplement labels wrong?

B Grade B: often enough to matter. When a lab measured 31 melatonin supplements, more than 71% fell outside 10% of the labelled amount, ranging from 83% less to 478% more, and one product varied by as much as 465% from lot to lot. Serotonin, a related brain chemical the authors describe as a controlled substance, turned up in 8 of them (Erland 2017). Of 44 weight-loss supplements bought in stores on or near 12 US military bases, 36 (82%) had inaccurate labels: 27 listed ingredients that weren't found and 16 contained hidden ingredients. None carried a third-party seal (Crawford 2024).

Freshness is a quality problem too. Among 72 fish and algae oil supplements, 68% of flavoured ones and 13% of unflavoured ones were over an industry limit for oxidation, the breakdown that makes oil go rancid (Hands 2024). C Grade C, from one study. See our fish oil page.

Which supplements are most likely to hide drugs?

B Grade B: sexual enhancement, weight loss and muscle-building products. From 2007 to 2016, the FDA flagged 776 supplements with hidden drug ingredients from 146 companies: 45.5% sold for sexual enhancement, 40.9% for weight loss and 11.9% for muscle building. The usual hidden drugs were sildenafil (the drug in a prescription erection pill), sibutramine (a weight-loss drug) and steroids. Of 28 products flagged again more than 6 months later, 19 had new hidden ingredients (Tucker 2018).

By 2021 the count had reached 1,068 products. Sibutramine, withdrawn from the market over heart risks, was the most common in weight-loss products, and a single sexual enhancement product could contain up to 5 drugs (White 2022). The FDA warns that sexual enhancement and "stamina" products are likely to contain dangerous hidden ingredients (FDA). Our weight-loss supplements guide covers that category.

Do sports supplements contain banned substances?

B Grade B: some do. Lab studies have found anabolic agents or other substances banned in sport in 14% to 50% of supplement samples tested (Jagim 2023). When researchers bought 66 higher-risk products from Dutch web shops, ones claiming to change hormones, build muscle, increase fat loss or raise energy, 25 (38%) contained undeclared doping substances, mostly stimulants (Duiven 2021). If you are tested for drugs in sport or at work, a positive test is your problem, not the label's. Choose products from a sport testing programme and check the batch.

What does "third-party tested" mean?

C Grade C that it lowers your risk. It means an independent organisation, not the company, tested the product. No regulator requires this, and each programme has its own testing rules, so the seal's name matters more than the words "third-party tested" on a label (Eichner 2019). Reviewers advise clinicians and athletes to choose products verified by a third party (Brykman 2022; Jagim 2023). The main US programmes:

• USP Verified: run by the US Pharmacopeia (USP). Search its list at quality-supplements.org.
• NSF: product certification for supplements, plus NSF Certified for Sport, which tests for substances banned in sport and lets you search by lot number (NSF Certified for Sport; NSF listings).
• Informed Sport and Informed Choice: sport programmes; Informed Sport says it tests every batch for banned substances before release, and you can search by batch number (Informed Sport).
• BSCG: a "Certified Drug Free" programme for sport (BSCG).

A seal covers one product, not a whole brand, and it says nothing about whether the supplement works. We don't list which products hold which seal: the programmes' own sites are the record, and listings change.

How do I check if a supplement is third-party tested?

1. Find the programme's name on the label, not just the words "tested" or "verified".
2. Search for the exact product on that programme's website (links above). A seal in a product photo is not proof.
3. For sport, match the batch or lot number printed on your bottle; NSF Certified for Sport and Informed Sport both let you search by it.
4. Search the FDA's Health Fraud Product Database for the product and brand. It lists products cited in FDA warning letters, advisory letters, recalls and public notices, including those with undeclared ingredients (FDA).
5. Check FDA recalls and safety alerts.

How do I read a Supplement Facts label?

• Serving size first. Every amount on the panel is per serving, and a serving may be 2 or 3 capsules.
• Amount per serving and % Daily Value. The % DV is the amount divided by the set Daily Value (FDA). A high % DV is not a safety limit; the upper limit is.
• Proprietary blends. A blend only has to show its total weight, with its ingredients listed by weight from most to least, so you can't tell how much of each you get (FDA). Trial amounts are rarely knowable from a blend.
• Add up what you take. Vitamins A, D and B6, zinc, iron, magnesium, niacin and selenium all have adult upper limits, and the same nutrient often sits in several of your products. Check your stack against the upper limits.
• Disease claims. A product sold to treat a disease counts as a drug, even if it is labelled a supplement (FDA), so a label promising to fix an illness is a warning sign.

How do I report a problem with a supplement?

The FDA's advice: if you have a reaction, stop the supplement, get medical care or advice, and report it to the FDA (FDA). Report through MedWatch, the FDA's safety reporting programme, and tell your doctor. Problems are not rare: an estimated 23,005 US emergency department visits a year are linked to supplements, and weight-loss or energy products caused 71.8% of the visits for palpitations, chest pain or a racing heart (Geller 2015).

What we'd skip

• Sexual enhancement, "stamina" and weight-loss products sold as supplements. These are where the FDA most often finds hidden prescription drugs (Tucker 2018; White 2022).
• Hormone, "test booster" and fat-burner products if you are drug tested. More than a third of the higher-risk products bought in one study contained banned substances (Duiven 2021).
• Products that say "third-party tested" but name no programme you can check (Eichner 2019).
• Any product called "FDA approved". The FDA does not approve supplements (FDA).

Safety and interactions

• Supplements can interact with medicines, interfere with lab tests, and cause problems during surgery (FDA). Biotin is a well-known example for blood tests: see does biotin affect thyroid and troponin tests?
• A hidden drug is still a drug. It can interact with your medicines the way the real prescription would, without you knowing it is there (FDA).
• Liver injury from supplements is tracked in LiverTox; see our guide to supplements and your liver.
• Ask your pharmacist to check your supplements against your medicines. Don't stop a prescribed medicine on your own; ask the prescriber or pharmacist. If you are pregnant, breastfeeding, or under 18, ask a clinician.

When to see a doctor

• Chest pain, palpitations or a racing heart after a weight-loss or energy product: stop it and get care; these products cause most of the supplement-related emergency visits for heart symptoms (Geller 2015).
• Yellow skin or eyes, dark urine or unusual tiredness after starting a supplement: stop it and see a doctor; see our liver guide for the signs.
• Any reaction you think a supplement caused: stop it, get medical advice and report it to the FDA (FDA).
• Before surgery, tell the team every supplement you take.
• Pregnant, breastfeeding or under 18: ask a clinician before you start any supplement.

FAQ

Are supplements FDA approved? No. The FDA has no authority to approve supplements or their labels for safety and effectiveness before they are sold; companies are responsible for their products.

How do I know if a supplement is third-party tested? Look for a named programme such as USP Verified, NSF, Informed Sport or BSCG, then search for the exact product (and for sport, the batch or lot number) on that programme's own website. A seal in a photo is not proof.

Are supplement labels accurate? Often not. In one lab study, more than 71% of 31 melatonin products were off their label by more than 10%, and in another, 36 of 44 weight-loss products had inaccurate labels (grade B).

What is the difference between NSF Certified for Sport and Informed Sport? Both are sport programmes that test supplements for substances banned in sport, and both let you look up tested products. Each sets its own testing rules, so athletes should check what their sport's governing body accepts.

Which supplements are most likely to contain hidden drugs? Sexual enhancement and weight-loss products, according to FDA warning data from 2007 to 2021; muscle-building products were common before 2017 (grade B).

Related pages

• Supplements and your liver · Weight-loss supplements · Does biotin affect thyroid and troponin tests?
• Melatonin · Fish oil
• Check my stack · How we grade

Sources

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2. Crawford C, et al. Label Accuracy and Quality of Select Weight-Loss Dietary Supplements Sold on or near US Military Bases. Nutrients. 2024. PubMed 39770990 · doi:10.3390/nu16244369
3. Tucker J, et al. Unapproved Pharmaceutical Ingredients Included in Dietary Supplements Associated With US Food and Drug Administration Warnings. JAMA Netw Open. 2018. PubMed 30646238 · doi:10.1001/jamanetworkopen.2018.3337
4. White CM. Continued Risk of Dietary Supplements Adulterated With Approved and Unapproved Drugs: Assessment of the US Food and Drug Administration's Tainted Supplements Database 2007 Through 2021. J Clin Pharmacol. 2022. PubMed 35285963 · doi:10.1002/jcph.2046
5. Jagim AR, et al. Prevalence of adulteration in dietary supplements and recommendations for safe supplement practices in sport. Front Sports Act Living. 2023. PubMed 37841887 · doi:10.3389/fspor.2023.1239121
6. Eichner AK, et al. Essential Features of Third-Party Certification Programs for Dietary Supplements: A Consensus Statement. Curr Sports Med Rep. 2019. PubMed 31082891 · doi:10.1249/JSR.0000000000000595
7. Hands JM, et al. A Multi-Year Rancidity Analysis of 72 Marine and Microalgal Oil Omega-3 Supplements. J Diet Suppl. 2024. PubMed 37712532 · doi:10.1080/19390211.2023.2252064
8. Duiven E, et al. Undeclared Doping Substances are Highly Prevalent in Commercial Sports Nutrition Supplements. J Sports Sci Med. 2021. PubMed 34211326 · doi:10.52082/jssm.2021.328
9. Brykman MC, et al. What Should Clinicians Know About Dietary Supplement Quality?. AMA J Ethics. 2022. PubMed 35575569 · doi:10.1001/amajethics.2022.382
10. Geller AI, et al. Emergency Department Visits for Adverse Events Related to Dietary Supplements. N Engl J Med. 2015. PubMed 26465986 · doi:10.1056/NEJMsa1504267