Supplements in the US are sold without pre-market FDA approval. Studies have repeatedly found products that contain less — or more — of an ingredient than the label claims, and occasionally contaminants or undeclared ingredients. Third-party testing is one of the few ways to know what’s in the bottle.
What the seals verify
USP Verified. The United States Pharmacopeia checks that a product contains the ingredients on the label in the stated amounts, doesn’t contain harmful levels of specified contaminants, breaks down properly in the body, and was made following good manufacturing practices.
NSF Certified. NSF International tests label accuracy and contaminants and audits manufacturing facilities. Its “Certified for Sport” program also screens for substances banned in competitive sport — useful for athletes, and a stricter standard in general.
ConsumerLab. An independent company that tests products and publishes results for subscribers; its seal indicates a product passed its testing.
What the seals don’t mean
A seal says nothing about whether a supplement works or is right for you. A perfectly manufactured product of an ineffective ingredient is still ineffective. Seals also don’t cover interactions with your medications.
Watch out for look-alikes
“Made in a GMP-certified facility” or “lab tested” are not the same as independent product certification. GMP compliance is a legal requirement for all supplement makers; it describes manufacturing processes, not verified contents. Check that a seal comes from a recognised organisation — you can usually search the product on the certifier’s website.
A practical approach
- Decide whether a supplement is worth trying, based on evidence for your specific concern.
- Choose a form and dose supported by research, clearly printed on the label.
- Prefer products with independent certification.
- Tell your clinician or pharmacist what you’re taking.