Third-Party Tested Supplements: What USP, NSF and GMP Marks Mean
GMP: the legal baseline
US supplement makers must follow current good manufacturing practice, set out in 21 CFR Part 111. It covers facilities, quality control, testing of ingredients and records. A company can state it follows GMP, but a mark on a label does not show an inspection result. The FDA's questions and answers explain that supplements are not approved before sale.
Third-party programs
Independent organizations such as USP and NSF run voluntary programs. Typically they audit the facility, test product samples for identity, strength and contaminants and let the product carry a mark. These programs are separate from the seller, which is the point. Always verify the product in the program's own public directory instead of trusting a logo on a web page.
Seals on a sales page
Sales pages often show round seals for GMP, natural or non-GMO. A graphic by itself is not a certificate. The HoneyPezil materials display GMP, natural-formula and GMO-free marks; the order page does not publish certificate numbers, so we treat them as the seller's statements, not independent verification.
What to ask a seller
- Which lab tested the product and for what?
- Can you share a certificate of analysis for my lot number?
- Who manufactures the product and where?
- Is any independent mark verifiable in a public directory?
Use official tools
The NIH's Dietary Supplement Label Database lets you look up labels, and the FDA posts recalls and safety alerts. See how to check alerts.
Reading a certificate of analysis
A certificate of analysis lists the lot number, tests run, methods and results, for example identity, heavy metals and microbes. Check that the lot matches your bottle, that the lab is named and that the date makes sense. A generic certificate with no lot is weak evidence.
What to do if a seller refuses
Consider whether you are comfortable buying without documents. A refund window helps, but it does not replace testing.
Frequently asked questions
Sources
- eCFR: 21 CFR Part 111, supplement current good manufacturing practice
- FDA: Questions and answers on dietary supplements
- NIH Dietary Supplement Label Database (DSLD)
- FDA: Recalls, market withdrawals and safety alerts
General information, not medical advice. Offer details were checked on November 11, 2026; confirm on the order page and read the label on your bottle. See our disclaimer and how we research.