What Is a Certificate of Analysis (COA)? How to Read One
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Certificate of analysis (COA)

Also called COA, CoA, lab report, third-party test · Reviewed

Definition: A certificate of analysis (COA) is a document listing test results for one batch (lot) of a product: what it is, how pure it is, how much is there, and sometimes whether it is sterile and low in endotoxin. A COA is only as good as the lab behind it and only covers the lot number printed on it.

What the lines usually mean

Common COA lines
LineWhat it answersTest often named
IdentityIs this the molecule it claims to be?Mass spectrometry
PurityWhat share of what was detected is the target peptide?HPLC
Content or assayHow many mg are in the vial?Quantitative HPLC or LC-MS
SterilityDid any live germs grow from the sample?Microbial growth test
EndotoxinHow much bacterial toxin is present?LAL test, in EU per mg or per mL

Purity and content are different questions. A vial can be high purity and still hold less than the label says.

What a COA cannot prove

Even licensed drug makers cannot simply trust a supplier's COA. Under 21 CFR 211.84, a manufacturer may accept a supplier's report of analysis only if it runs at least one identity test itself and checks the supplier's results at intervals.

Paper is not proof. In one study, three semaglutide vials bought online claimed 99% purity on their labels; testing found 7.7% to 14.37% (Ashraf 2024).

  • Check that the lot number on the COA matches the vial.
  • Check the test date and the lab name.
  • Note which lines are missing. A COA with purity only says nothing about sterility or endotoxin.

Why it matters when you track doses

Save the lot number with each vial you log. If you get an injection site reaction or a vial behaves differently, you can tell which batch it came from.

General education drawn from labels and published studies, not personal medical advice. Your prescriber, pharmacist and the label that came with your product are the final word.
HPLC purityHPLC purity is the percent of a sample that is the intended compound, measured by high-performance liquid… Mass spectrometry (MS)Mass spectrometry (MS) is a lab method that weighs molecules. It turns molecules into charged particles… EndotoxinEndotoxin is a substance from the outer wall of certain bacteria (gram-negative bacteria), released when… Research use only (RUO)Research use only (RUO) is a label phrase. In US rules it comes from labeling for in vitro diagnostic… Compounding pharmacyA compounding pharmacy makes a medicine from raw ingredients for a specific patient, rather than…

Frequently asked questions

Does a COA mean a product is safe?+
No. It reports specific tests on one lot. Missing tests, a different lot or an unreliable lab all limit what it tells you.
What is a third-party COA?+
A report from a lab that is not the seller. It removes one conflict of interest but still covers only the sample that lab tested.
Do compounding pharmacies get COAs?+
Yes. Federal law requires 503A pharmacies to have a certificate of analysis for each bulk drug ingredient they use.

Sources

  1. 21 CFR 211.84: testing of components, including supplier reports of analysis, eCFR via Cornell LII
  2. Ashraf et al. J Med Internet Res 2024 (semaglutide vials bought online without a prescription: LC-MS, sterility and endotoxin tests). PMID 39509151
  3. 21 USC 353a: pharmacy compounding (section 503A), Cornell LII

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