Supplement testing glossary
Plain-English definitions of the terms that come up across supplement testing and compliance — clickable everywhere they appear in our guides.
Regulatory
21 CFR 111
The FDA's Good Manufacturing Practice regulation for dietary supplements - the rulebook for testing and quality.
GMP
Good Manufacturing Practice - the system of facility, process, and testing controls the FDA requires.
Form 483
The list of objectionable conditions an FDA investigator hands you at the end of an inspection.
Warning Letter
A public FDA enforcement notice - more serious than a 483 - that stays online permanently.
Prop 65
California's chemical-warning law, with heavy-metal limits far stricter than federal standards.
DSHEA
The 1994 law that created the modern dietary-supplement category and its claim rules.
Structure/Function Claim
A claim about how an ingredient affects the body's structure or function - allowed with substantiation + a disclaimer.
Tests
Heavy Metals
Testing for toxic elements - lead, arsenic, cadmium, and mercury - that bioaccumulate in botanical ingredients.
Potency Testing
Verifying that the amount of active ingredient matches the label claim - usually by HPLC.
Identity Testing
Confirming an ingredient is actually what the label says it is - required for every dietary ingredient.
Microbial Testing
Screening for harmful microbes - total count, yeast and mold, E. coli, Salmonella.
Stability Testing
Studying how a product degrades over time to set a defensible expiration date.
CFU
Colony-Forming Unit - the count of viable microbes, used to verify probiotic potency claims.
Water Activity
A measure of free moisture that predicts microbial and mold risk - critical for gummies.
Methods
ICP-MS
Inductively coupled plasma mass spectrometry - the gold-standard method for heavy-metal testing.
HPLC
High-performance liquid chromatography - the standard method for measuring active-ingredient potency.
HPTLC
High-performance thin-layer chromatography - a botanical fingerprinting method used for identity testing.