GMP is the floor, not the ceiling. It is the minimum operational standard a manufacturer must meet to legally produce dietary supplements, cosmetics, foods, and drugs in the U.S. It covers everything from how the floor is sealed to how the batch records are signed.

21 CFR Part 111 — the federal regulation for dietary supplement GMP — runs to about 95 pages. The major sections cover: physical plant design and sanitation, equipment qualification and cleaning validation, personnel training and hygiene, raw material identity testing and quarantine, master manufacturing records (MMR), batch production records (BPR), in-process and finished product testing, complaint handling, and recall procedures.

FDA inspections happen on a risk-based schedule. A facility producing high-risk products (probiotics, peptides, sterile drugs) gets inspected more frequently than one producing low-risk products (vitamin C tablets, basic protein powder). An inspection finding is documented on a Form 483, and the manufacturer has 15 working days to respond.

Third-party GMP audits add another layer. NSF, NPA, and USP all run GMP certification programs. A manufacturer can be FDA-inspected and have an NSF GMP registration on top — those are different audits against overlapping but distinct standards. When evaluating a manufacturer, ask for both the FDA registration number and the third-party GMP certificate.