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Glossary

What is a certificate of analysis (COA)?

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

A certificate of analysis (COA) is a document that reports test results for a specific production lot of an ingredient or product. When a supplement maker relies on a supplier's COA, FDA's rule (21 CFR 111.75) says the certificate must list the test methods used, the limits each result is judged against, and the actual results.1,2

Key facts

  • A maker may rely on a supplier's certificate only after confirming the supplier's results with its own tests, and it must reconfirm them from time to time.1
  • A certificate cannot stand in for the maker's own identity check of a dietary ingredient. At least one test or examination is required before use.1,3
  • FDA's 2003 proposal would not have allowed supplier certificates at all, because of problems with faulty certificates in the past.3
  • FDA does not test supplements before they are sold. It suggests asking the manufacturer, or a commercial laboratory, for an analysis of a product's content.4
  • Results below a method's detection limit are commonly reported as not detected, and results between the detection and quantitation limits as trace.5

What a COA contains

A COA is tied to a lot. FDA defines a lot as a batch, or an identified part of one, that is uniform and meant to meet the same specifications for identity, purity, strength and composition. The lot number is the code that links the results to that lot's manufacturing history.2

When a manufacturer relies on a supplier's certificate instead of running every test itself, FDA requires the certificate to show at least three things:1

  • the test or examination method used for each item, so a reader can tell how it was measured;1
  • the limit, or specification, that each result is compared with;1
  • the actual result of each test or examination.1

Those three items are the minimum FDA sets. It also helps to see who issued the certificate and when the testing was done, so you know who stands behind the numbers.1

How to read the results

Each line pairs a test with a limit and a result. A result written as not detected, or ND, means the amount was below the lowest level the method can reliably detect. It does not prove the amount is zero.5

A result marked trace sits between the detection limit and the quantitation limit, where the method can see something but cannot put a reliable number on it. Above the quantitation limit, labs report a number, usually with an uncertainty at about 95% confidence.5

Check the units. Contaminants are often reported as a concentration, such as micrograms per gram, so the amount in a day depends on how many grams you take. California's Proposition 65 rules, for example, work out exposure by multiplying the concentration by how much an average user takes.6

What a COA does not tell you

A certificate describes the samples that were tested. FDA expects samples to be representative, meaning drawn by rational criteria such as random sampling so they portray the whole material. Results for one lot say nothing directly about another lot.2

It also covers only the tests listed on it. A report with heavy metals and microbes but no strength result says nothing about how much of the main ingredient is present, because FDA sets identity, purity, strength, composition and contaminant limits as separate specifications.7

Words on a label such as verified or certified are not the same as results. NCCIH notes that such terms do not necessarily guarantee quality or consistency.8

Questions people ask

Who issues a certificate of analysis?

It varies. FDA's rule describes certificates that come from an ingredient supplier and are relied on by the manufacturer, which must first confirm the supplier's results. Whoever issues one, the useful parts are the method, the limit and the actual result for each test.1

Does ND on a COA mean none is present?

No. Not detected means the amount was below what the method could reliably detect. A method with a lower detection limit might still find a small amount.5

Should the lot number on a COA match my container?

The results describe the lot named on the certificate. If the numbers differ, the certificate is about a different production run.2

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Sources

  1. 21 CFR 111.75. What must you do to determine whether specifications are met? Opened 2026-10-07.
  2. 21 CFR 111.3. What definitions apply to this part? Opened 2026-10-07.
  3. Food and Drug Administration. Current Good Manufacturing Practice in Manufacturing, Packaging, Labeling, or Holding Operations for Dietary Supplements; Final Rule. Federal Register 72 FR 34752, June 25, 2007. Opened 2026-10-07.
  4. U.S. Food and Drug Administration. Questions and Answers on Dietary Supplements. Content current as of August 27, 2026. Opened 2026-10-07.
  5. U.S. Food and Drug Administration. Elemental Analysis Manual, Section 3.2: Terminology. Version 3.0, December 2021. Opened 2026-10-07.
  6. Office of Environmental Health Hazard Assessment. Regulations on Proposition 65, California Code of Regulations, Title 27, Division 4, Chapter 1, with Appendix A, Proposition 65: A Summary. Unofficial copy, updated February 2025. Opened 2026-10-07.
  7. 21 CFR 111.70. What specifications must you establish? Opened 2026-10-07.
  8. National Center for Complementary and Integrative Health. Using Dietary Supplements Wisely. Last updated January 2019. Opened 2026-10-07.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.