Supplement Science · Explainer
What Third-Party Testing Actually Verifies
NSF, Informed Sport and USP test different things. "Made in a cGMP facility" tests nothing about your bottle.
By Julien Malet, · Updated 2026-09-08
Supplements in the US are not approved before sale. The FDA can act against a product after the fact, but nobody checks the bottle on the way out. That makes independent verification meaningful — and makes the difference between real certification and certification-flavoured marketing worth knowing.
The seals that mean something
NSF Certified for Sport. Tests the finished product against its label, screens for over 280 banned substances, and audits the manufacturing facility. Batch-level testing. The strongest widely available mark, and the one most professional sports organisations point to.
Informed Sport / Informed Choice. Batch-tests for banned substances. Informed Sport tests every batch; Informed Choice samples periodically. Strong on contamination, less focused on whether label amounts are accurate.
USP Verified. Verifies identity, potency, purity and that the product will dissolve and release its contents. Rare in sports supplements, more common in vitamins.
ConsumerLab, Labdoor. Independent testing organisations rather than certifiers. They buy products and publish results, which is genuinely useful — but a brand cannot display a seal, so absence means nothing.
The phrases that mean much less
"Made in a cGMP-certified facility." cGMP — current Good Manufacturing Practices — is a set of process requirements every US supplement facility is already legally required to follow. It is a floor, not a distinction, and it says nothing about whether your bottle contains what the label claims.
"NSF registered facility." Registration of the facility, not certification of the product. Different, weaker claim, easily confused with NSF Certified for Sport — sometimes deliberately.
"Made in the USA." Where it was manufactured. Not what is in it.
"Lab tested." By whom? A manufacturer testing its own product and publishing the result is a marketing document. Meaningful when independent and batch-specific; meaningless otherwise.
"Clinically proven." Almost always means an ingredient in it has been studied, not that this formula has. A study on citrulline is not a study on the product containing citrulline. Watch for this one — it is the most common conflation in the category.
Why contamination testing matters more than you would think
This is not a theoretical concern. Independent analyses have repeatedly found supplements containing undeclared substances — stimulants, steroid analogues, prescription drug ingredients — and the categories most affected are weight loss, sexual enhancement and pre-workout.
Two groups should treat a banned-substance seal as non-negotiable: tested athletes, where a contaminated product ends a career and "I didn't know" is not a defence, and anyone taking prescription medication, where an undeclared active ingredient is an interaction nobody can plan for.
The sexual-enhancement category has a specific version of this problem: undeclared sildenafil or tadalafil analogues turn up in products marketed as "all natural," and the FDA has issued many warnings about it. In someone taking nitrates, that is a dangerous blood-pressure interaction from a bottle that never disclosed the ingredient.
How to check a seal
Do not trust the logo on the label — verify it in the certifier's own database. NSF, Informed Sport and USP all publish searchable lists of certified products.
A seal on a package is an image file. The database entry is the fact.
Where to put this in your decision
Third-party testing is check five of six, and the order matters. A certified product that is underdosed is still underdosed — certification verifies that the label is accurate, not that the formula is worth taking.
Get the dose right first. Then ask who verified it.