A supplement label is a promise: this capsule contains this ingredient, at this amount, and nothing that shouldn't be there. Analytical testing is how that promise is verified — turning a marketing claim into a defensible, data-backed fact.
Why dietary supplement testing matters
Under the FDA's current Good Manufacturing Practice rule for dietary supplements (21 CFR Part 111), manufacturers must establish specifications for identity, purity, strength, and composition — and confirm those specifications with appropriate tests before a product is released. In practice that means answering three questions for every lot: Is it the right ingredient? Is it present at the labeled amount? Is it free of contaminants? A laboratory result is the evidence behind each answer.
Identity: is the ingredient what the label claims?
Botanicals are the hardest category to get right. Closely related species look identical once dried and milled, common names map to several plants, and a cheaper species is easy to substitute for a premium one. Laboratories confirm identity with orthogonal methods: HPTLC (high-performance thin-layer chromatography) for a visual chemical fingerprint, DNA barcoding for species-level confirmation, and microscopy or organoleptic checks for raw materials.
The problem is not hypothetical. Ginseng is one of the best-documented cases: a 2025 review by the ABC–AHP–NCNPR Botanical Adulterants Prevention Program pooled 48 peer-reviewed studies covering 911 commercial ginseng products. Of those tested for botanical adulterants, about one in four were adulterated — and in a separate subset screened for drugs, nearly half contained undeclared pharmaceutical ingredients:
Figure
Ginseng authenticity: findings from a global review (911 commercial products)
Values in % of products tested
211 of 853 commercial ginseng products tested for botanical adulterants.
28 of 57 products in a separate screen for drug adulteration.
Ginseng is a well-studied example; rates differ by botanical, market, and method — but they show identity cannot be assumed from a label alone.
Source: ABC–AHP–NCNPR Botanical Adulterants Prevention Program review — Orhan, Gafner & Blumenthal, Natural Product Communications (2025).
Much of this is economically motivated adulteration — diluting an expensive extract with a cheaper one, bulking with starch or maltodextrin, or spiking a weak botanical with a purified compound so it passes a potency test it would otherwise fail. Identity testing that only measures a single marker compound can be fooled; a fingerprint-plus-confirmation approach is much harder to game.
Potency: does it meet label claim?
Once identity is confirmed, quantitative methods measure how much active is actually present. HPLC and UHPLC separate and quantify actives against certified reference standards; LC-MS/MS adds sensitivity and specificity for trace analytes and difficult matrices; and GC / GC-MS handles volatiles and fatty-acid profiles. Results are compared to the label claim and to any applicable compendial specification (for example, a USP monograph). Two failure modes matter here: under-potency from poor raw material or degradation, and unnecessary over-formulation, where a large overage hides a process that isn't in control.
Purity and safety
The same lot has to be clean, not just correct. A complete program screens for:
- Heavy metals — lead, arsenic, cadmium, and mercury by ICP-MS. See our heavy-metals guide.
- Microbial quality — total counts plus absence of specified pathogens. How rapid microbiology works.
- Pesticide residues and residual solvents for botanicals and extracts.
- Declared allergens and undeclared adulterants relevant to the ingredient.
What makes a result defensible
A number on a certificate of analysis is only as trustworthy as the system behind it. Defensible results come from validated, fit-for-purpose methods run against traceable reference standards, in a laboratory whose competence is independently assessed.
Accreditation is the backstop
ISO/IEC 17025 accreditation means an independent body has evaluated the lab's methods, equipment, and quality system. It's what lets a buyer, an auditor, or a regulator rely on the result without re-testing it themselves — and it's the difference between a claim and proof.
References
- 1.FDA — 21 CFR Part 111, cGMP for Dietary Supplements (eCFR)
- 2.Orhan, Gafner & Blumenthal (2025) — Ginseng Adulteration Across Global Markets, Natural Product Communications
- 3.ABC–AHP–NCNPR Botanical Adulterants Prevention Program (BAPP)
Educational content. Regulatory limits and methods referenced are current at time of writing; confirm the applicable standard for your product and market.
