How to Read a Supplement Label (and Spot Red Flags)

Key takeaways

• The FDA does not have the authority to approve dietary supplements before they are marketed.^[1]
• A proprietary blend only has to list its total weight and its ingredients in descending order by weight, not the amount of each.^[3]
• Structure/function claims such as "supports metabolism" must carry an FDA disclaimer; supplements may not claim to treat or prevent disease.^[4]
• Quality seals from USP, NSF or ConsumerLab check contents and contaminants, but the NIH says they do not mean a product is safe or effective.^[2]
• Of 317 adulterated weight-loss supplements in FDA warnings from 2007 to 2016, 84.9% contained sibutramine.^[8]

In short: Start with the Supplement Facts panel: check the serving size, the amount of each ingredient, and whether key ingredients hide inside a “proprietary blend” that shows only a total weight. Then read the claims: “supports metabolism” is a legal structure/function claim that the FDA has not evaluated, while a claim to treat a disease is not allowed on a supplement. Look for an independent quality seal such as USP, NSF or ConsumerLab, which checks contents but not whether the product works. Treat fast weight-loss promises and “drug-like” effects as red flags: the FDA has found hidden prescription drugs in hundreds of weight-loss supplements.

Weight-loss supplements are a crowded shelf, and labels are written to sell. This guide walks through every part of a U.S. supplement label, what the law requires on it, and the warning signs regulators look for. For what the evidence says about specific ingredients, see our supplements hub and the broader weight-loss pills guide. It is general education, not advice about any product: check with a pharmacist or clinician before taking a supplement, especially with prescription medicines.

First, what “dietary supplement” means legally

Under the 1994 Dietary Supplement Health and Education Act (DSHEA), supplements are regulated as a kind of food, not as drugs. The FDA states that it does not have the authority to approve dietary supplements before they are marketed; companies are responsible for making sure their products are safe and their labels truthful. The NIH Office of Dietary Supplements (ODS) puts the contrast simply: medicines must be approved by the FDA before they can be sold, supplements do not. So the label is the main information you get, and knowing how to read it matters.

The Supplement Facts panel, annotated

Below is a made-up example label for a typical “metabolism” capsule, followed by what each numbered part tells you. It is not a real product.

1. Serving size. Federal rules require “Serving Size” right under the “Supplement Facts” heading. Every amount on the label is per serving, so if a serving is two or three capsules, a bottle may last half as long as you think, and the dose in one capsule is a fraction of what is listed. The ODS notes that the maker suggests the serving size, but your health care provider might decide a different amount is right for you.
2. % Daily Value. Vitamins and minerals with established daily values show a percentage. Ingredients without one, such as most herbs and caffeine, carry a symbol pointing to “Daily Value not established”. Very high percentages are not a sign of a better product, and more is not always safer.
3. Proprietary blend. A blend may be listed under a trademark-style name with only the total weight of its ingredients. The rule requires the ingredients to be listed in descending order of weight, but not the amount of each. In the example, you can’t tell whether the 850 mg is mostly caffeine or mostly pepper extract, or whether any ingredient is present in the amount used in studies. For caffeine, that matters: the FDA cites 400 mg a day as an amount not generally associated with negative effects for most adults.
4. Plant parts and other ingredients. Botanical ingredients must name the part of the plant used (leaf, root, fruit), which matters because parts can differ. “Other ingredients” lists fillers, binders, capsules and flavors; check it for allergens and, if you avoid animal products, gelatin.
5. Claims and the disclaimer. Phrases like “supports metabolism” or “helps maintain healthy weight” are structure/function claims. They must carry the FDA disclaimer that begins “This statement has not been evaluated by the Food and Drug Administration”, and the company must notify the FDA within 30 days of first marketing them. That notice is not an approval.
6. Who made it, and any seal. Look for the company’s name and a U.S. address or phone number so you can ask questions or report a problem, plus any independent quality seal (see below).

Structure/function claims vs disease claims

This is the single most useful distinction on the label. Under 21 CFR 101.93, a supplement may describe how an ingredient affects the normal structure or function of the body, but it may not claim to diagnose, treat, mitigate or prevent a disease; a product that makes a disease claim is regulated as a drug. The FDA’s definition is broad: a claim can be a disease claim through the product name, pictures or symbols, or by saying the product is a substitute for a disease therapy or works like a particular drug.

Wording you might see	What kind of claim	What to think
“Supports a healthy metabolism”	Structure/function	Legal with the disclaimer; not FDA-evaluated, so look for human trials
“Helps curb cravings”	Structure/function	Same: ask for the evidence
“Treats obesity” or “lowers blood sugar in diabetes”	Disease claim	Not allowed on a supplement; a red flag
“Works like Ozempic” or “a natural GLP-1”	Implies it substitutes for a drug therapy	A red flag; see our “nature’s Ozempic” explainer
“Lose 30 pounds in 30 days”	Fast-loss promise	The FTC lists this kind of promise among claims that are always false

Quality seals: what they check, and what they don’t

Because the FDA doesn’t test supplements before sale, some companies pay independent organizations to test them. The ODS names three that offer quality testing: ConsumerLab.com, NSF International and U.S. Pharmacopeia (USP). A seal indicates the product was properly manufactured, contains the ingredients listed on the label and does not contain harmful levels of contaminants. USP describes its Verified Mark as covering identity, strength, purity and how well a tablet breaks down, and NSF’s certification includes a label-claim review and testing for contaminants and undeclared ingredients; its Certified for Sport program also screens for substances banned in sport.

What a seal does not do: the ODS stresses that these seals do not mean a product is safe or effective. A perfectly made capsule of an ingredient with weak evidence is still an ingredient with weak evidence. Use a seal to answer “is what’s on the label in the bottle?”, and the research to answer “does it work?” Our pages on fat burners, green tea extract, berberine and fiber supplements rate the evidence for common ingredients.

Red flags for hidden drugs

Weight-loss products are one of the categories most often found with hidden prescription drugs. A 2018 analysis of the FDA’s tainted-products database found 776 adulterated supplements from 2007 to 2016; 317 were sold for weight loss, and 84.9% of those contained sibutramine, a prescription diet drug withdrawn in 2010 because of heart attack and stroke risk. Other hidden ingredients have included the laxative chemical phenolphthalein and the antidepressant fluoxetine. Recalls don’t always fix the problem: when researchers bought 27 recalled supplements an average of 34 months after their FDA recall, 18 of them, two thirds, still contained a banned drug.

• Still contained a banned drug1867%
• No banned drug found933%

Recalled supplements still on sale years later: what testing found

Item	Value
Still contained a banned drug	18
No banned drug found	9

18 of 27 (66.7%) contained one or more pharmaceutical adulterants, including sibutramine and its analogs, phenolphthalein and fluoxetine.

Source: Cohen PA et al., JAMA 2014 (27 recalled supplements bought a mean of 34 months after FDA recall) (checked on October 7, 2026)

The FDA’s “6 tip-offs to rip-offs” give the warning signs to watch for:

• One product does it all, treating a long list of unrelated problems.
• Personal testimonials in place of scientific evidence; success stories are easy to make up.
• Quick fixes such as “lose 30 pounds in 30 days”.
• “All natural” used as proof of safety.
• Words like “new discovery”, “secret ingredient” or promises of sure results.
• Conspiracy claims that doctors or the government don’t want you to know.

Where the tainted products came from is telling too: in 2014 to 2016, 38.6% of the adulterated samples in the 2018 analysis were found through online sampling and 34.3% in international mail shipments. So be extra careful with products sold only online, shipped from abroad or labeled in a language you can’t read, and with any product whose effects feel like a strong drug. Before buying, search the product name in the FDA’s tainted-products notifications (our detox tea page explains how they work), but remember the FDA says its list covers only a small fraction of contaminated products.

Check for interactions

“Natural” does not mean it can’t interact with medicines. The ODS gives examples: vitamin K can reduce how well the blood thinner warfarin works, and St. John’s wort can speed the breakdown of many medicines, including some antidepressants, birth control pills and heart medicines, making them less effective. Berberine, a popular “metabolism” ingredient, can change levels of some prescription drugs; our berberine page has details. Bring the bottle, not just the name, to your pharmacist.

A 60-second label check

The bottom line

A supplement label tells you what the maker says is inside, not whether it works. Read the serving size and amounts, be wary of proprietary blends, know the difference between a structure/function claim and a disease claim, and use quality seals for what they are. If a product promises fast or drug-like weight loss, walk away. For proven options, our lose weight hub covers food and activity, and our guide to choosing a weight-loss program helps you find support. To see every kind of option side by side, try our Find My Options tool, and talk with your clinician about what fits you.

Questions to ask a professional

• Could this supplement interact with any of my medicines?
• Is the dose on this label safe for me, given my heart, liver or kidney health?
• Is there good evidence that this ingredient helps with weight?
• Are there proven options I should consider instead?

Frequently asked questions

Are weight-loss supplements approved by the FDA?

No. The FDA does not have the authority to approve dietary supplements before they are sold. Companies are responsible for safety and truthful labels, and the FDA acts after problems are found.

What is a proprietary blend?

A group of ingredients listed under one name with only the total weight. The ingredients must appear in descending order by weight, but you can't tell how much of each is in a serving.

What does "This statement has not been evaluated by the FDA" mean?

It is the required disclaimer for structure/function claims such as "supports metabolism". The company notifies the FDA that it uses the claim, but the FDA has not reviewed whether it is true.

Does a USP or NSF seal mean a supplement works?

No. A seal means the product was tested for what is on the label and for harmful contaminants. The NIH says seals do not mean a product is safe or effective.

How can I tell if a supplement has hidden drugs?

You often can't from the label. Be wary of fast-loss or drug-like claims and effects, search the FDA tainted-products notifications, prefer quality-tested products, and ask a pharmacist.

References

1. Questions and Answers on Dietary Supplements. U.S. Food and Drug Administration. (accessed October 7, 2026) Government page
2. Dietary Supplements: What You Need to Know (updated January 4, 2023). NIH Office of Dietary Supplements. (accessed October 7, 2026) Government page
3. 21 CFR 101.36: Nutrition labeling of dietary supplements. U.S. Food and Drug Administration (Electronic Code of Federal Regulations). (accessed October 7, 2026) Government page
4. 21 CFR 101.93: Certain types of statements for dietary supplements. U.S. Food and Drug Administration (Electronic Code of Federal Regulations). (accessed October 7, 2026) Government page
5. Spilling the beans: how much caffeine is too much?. U.S. Food and Drug Administration. (accessed October 7, 2026) Government page
6. USP Verified Mark (dietary supplements). U.S. Pharmacopeia. (accessed October 7, 2026) Other
7. Dietary Supplement and Vitamin Certification. NSF. (accessed October 7, 2026) Other
8. Tucker J, Fischer T, Upjohn L, et al.. Unapproved Pharmaceutical Ingredients Included in Dietary Supplements Associated With US Food and Drug Administration Warnings. JAMA Network Open, 2018. doi:10.1001/jamanetworkopen.2018.3337 · PMID 30646238 (accessed October 7, 2026) Other
9. Cohen PA, Maller G, DeSouza R, Neal-Kababick J. Presence of banned drugs in dietary supplements following FDA recalls. JAMA, 2014. doi:10.1001/jama.2014.10308 · PMID 25335153 (accessed October 7, 2026) Other
10. 6 Tip-offs to Rip-offs: Don’t Fall for Health Fraud Scams (content current as of 03/04/2021). U.S. Food and Drug Administration. (accessed October 7, 2026) Government page
11. Weight loss product notifications (tainted products). U.S. Food and Drug Administration. (accessed October 7, 2026) Government page
12. The Truth Behind Weight Loss Ads. Federal Trade Commission. (accessed October 7, 2026) Government page
13. Public Notification: Lingzhi Cleansed Slim Tea Contains Hidden Drug Ingredient. U.S. Food and Drug Administration, 2014. (accessed October 7, 2026) Government page

Facts checked on October 7, 2026

Educational information, not medical advice. Talk with a qualified healthcare professional about your own situation. In an emergency call 911.