QUALITY

How do you choose a supplement you can trust? cGMP, testing and labels

What the FDA does and doesn't check, what cGMP and third-party testing mean, why proprietary blends hide amounts, and a simple checklist for picking a supplement you can trust.

The short version

The FDA does not approve dietary supplements before they are sold. Companies are responsible for safety and honest labels, so quality varies a lot between products.
Look for a product made under current good manufacturing practices (cGMP, the FDA's 21 CFR Part 111 rules), a full label with every ingredient and amount, and ideally independent third-party testing.
Labels are not always accurate: in a 2023 study of 25 melatonin gummies, 22 (88%) were mislabeled, with actual melatonin ranging from 74% to 347% of the label.
Skip proprietary blends when you can. US rules let a blend list only its total weight, so you can't see how much of each ingredient you're getting.
Be most cautious with products sold for weight loss, sexual enhancement or muscle building: of 776 supplements the FDA flagged for hidden drug ingredients from 2007 to 2016, most were in those three groups.

Does the FDA check supplements before they're sold?

No. Under the 1994 law that governs supplements, the FDA does not have the authority to approve dietary supplements before they are marketed, and it generally doesn't approve their labels or claims before use either.

Instead, the company is responsible for making sure its products are safe and its labels are truthful and not misleading. The FDA steps in afterward: it inspects manufacturing sites, monitors the marketplace, tests products and reviews reports of side effects.

That system puts more of the checking on you. The questions below are the ones that separate careful products from careless ones.

What does cGMP mean on a supplement?

cGMP stands for current good manufacturing practices: FDA rules (21 CFR Part 111) that anyone who makes, packages or holds dietary supplements must follow. They exist to help make sure a product has the identity, purity, strength and composition its label says.

In practice, cGMP covers things like checking incoming ingredients, keeping batch records, testing finished products and handling complaints. It is a legal requirement, not an optional extra, so a cGMP claim is a baseline rather than a bonus.

What cGMP doesn't tell you is whether an ingredient works or whether the dose suits you. It is about making the product correctly, not about choosing it well.

How accurate are supplement labels?

Often less accurate than people assume, especially for some product types. Independent lab studies keep finding gaps between the label and the bottle.

Melatonin gummies: a 2023 study in JAMA analyzed 25 products. Only 3 (12%) had melatonin within 10% of the labeled amount; the rest ranged from 74% to 347% of the label, and one contained no detectable melatonin at all.
Immune products: a 2022 study bought 30 immune-support supplements from a large online marketplace. 17 of 30 had inaccurate labels: 13 listed ingredients that weren't detected, and 9 contained substances not on the label. None carried a third-party certification seal.
Hidden drugs: from 2007 to 2016, the FDA identified 776 supplements containing unapproved drug ingredients. 45.5% were sold for sexual enhancement, 40.9% for weight loss and 11.9% for muscle building, and 20.2% contained more than one hidden drug.

NCCIH, part of the NIH, also notes that words like "standardized," "verified" or "certified" on a label do not by themselves mean a product is high quality or consistent.

What does third-party testing actually check?

Third-party testing means an independent lab or certification program, not the company itself, checks the product. It is one of the best signals of quality you can see from the outside.

Good programs generally confirm that the product contains the ingredients and amounts on the label and doesn't contain harmful levels of contaminants such as heavy metals or microbes. Some also audit the factory.

Testing has limits. It confirms that the label is accurate, not that the ingredient is useful for you or safe with your medicines. And a vague phrase like "lab tested" with no named program or results is much weaker than a specific, checkable certification.

Why should you avoid proprietary blends?

Because they hide the amount of each ingredient. Under FDA labeling rules (21 CFR 101.36), a proprietary blend can list its herbs and other non-vitamin ingredients in order of weight with only the total weight of the blend.

So a label might show a 500 mg blend of five ingredients without telling you whether the one you care about is 400 mg or 4 mg. That makes it hard to compare products, match amounts used in research, or check totals across everything you take.

A fully disclosed label lists every ingredient with its own amount and form, such as "magnesium (as magnesium bisglycinate) 350 mg." Apiece lists every ingredient and amount in each formula and uses no proprietary blends.

What are the red flags on a supplement label?

Claims that sound too good to be true usually are. The FDA advises being wary of hype and not assuming that "natural" means safe.

Promises of fast, dramatic results, or wording that implies the product works like a prescription medicine.
Products sold for weight loss, sexual enhancement or muscle building, the categories most often found with hidden drug ingredients.
Proprietary blends or missing amounts for key ingredients.
No company name, address or way to contact the maker.
Very high doses with no clear reason, or amounts above adult upper limits once you add up everything you take.
Vague quality words with nothing to check behind them.

A simple checklist before you buy

Choose products that are easy to verify and fit what you already take. Five quick checks cover most of it:

Made under cGMP by a company that names itself and can be contacted.
Every ingredient listed with its own amount and form, with no proprietary blends.
Independent third-party testing you can check, especially for herbs, gummies and sports products.
Amounts that make sense when added to your other supplements and fortified foods.
Reviewed with your doctor or pharmacist if you take medicines, are pregnant or breastfeeding, or have a health condition.

If you have a bad reaction to a supplement, stop taking it, tell your doctor and report it to the FDA. Supplement companies are required to forward serious adverse event reports they receive to the FDA within 15 days.

Apiece formulas are made to order in a certified US facility (cGMP), with every amount on the label and never more than 10 capsules a day.

Questions

Are dietary supplements regulated by the FDA?

Yes, but differently from medicines. The FDA does not approve supplements before they are sold. Companies must follow manufacturing rules (cGMP) and keep labels truthful, and the FDA inspects facilities, tests products and acts on problems after products reach the market.

What does cGMP certified mean on a supplement?

It means the product is made under current good manufacturing practices, the FDA's rules in 21 CFR Part 111 for making, packaging and holding supplements. These rules aim to make sure each product has the identity, purity, strength and composition on its label. They don't show whether an ingredient works for you.

Is third-party testing worth looking for?

Yes, it is one of the clearest quality signals. Independent programs generally confirm that a product contains what the label says in the stated amounts and isn't contaminated. It doesn't show that a product is effective or right for you, so still check doses and medicines with your pharmacist.

What is a proprietary blend on a supplement label?

It is a group of ingredients listed together with only the total weight of the blend. US labeling rules allow this, so you can't see how much of each ingredient is in the product. A fully disclosed label that lists every ingredient with its own amount is easier to compare and check.

Which supplements are most likely to contain hidden drugs?

Products sold for sexual enhancement, weight loss and muscle building. Of 776 supplements the FDA flagged for unapproved drug ingredients between 2007 and 2016, 45.5% were sexual enhancement products, 40.9% weight loss and 11.9% muscle building. Take extra care with these categories.

Sources

Build my formula More from the Journal

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This page is general information, not medical advice. Check with your doctor or pharmacist before starting a supplement, especially if you take medication, are pregnant or nursing, or have a health condition. Updated 2026-10-22.