Short answer: a useful peptide Certificate of Analysis (COA) identifies the exact product and lot that was tested, names the independent laboratory and the date, and reports at least an identity result and a purity result, with the methods used. If any of those are missing, the document cannot tie a result to the vial in front of you.
Product identity
The COA should name the compound and the labeled amount per vial (for example, “Tesamorelin 10 mg”). Blends should list every component. The name should match the product label, so there is no doubt about what was tested.
Lot or batch number
The lot number is what links a COA to a specific production batch. A COA without a lot number, or with a lot number that does not appear on your vial, only shows that some sample passed testing at some point. Look for a lot number printed in the report itself, not only in a file name.
Testing laboratory
The report should name the laboratory that performed the analysis, with contact details or a website. An independent third-party lab is stronger evidence than in-house testing, because it has no stake in the result.
Client
Most lab reports state the client who submitted the sample. This tells you who ordered the test. If the client is a different company from the seller, it is reasonable to ask how that sample relates to the product being sold.
Test and report dates
Dates show how recent the testing is. Many reports list both the date the sample was received and the date the report was issued.
Identity result
Identity testing confirms the sample is the compound it claims to be. Mass spectrometry (often LC-MS) is the most common method for peptides: it compares the measured molecular mass with the theoretical mass. See identity testing vs. purity testing.
Purity result
Purity is usually reported as a percentage from HPLC (high-performance liquid chromatography). It describes how much of the detected material is the target peptide. See how peptide purity testing works.
Content or quantity
Some COAs also report net peptide content, meaning how many milligrams of peptide are actually in the vial compared with the label claim.
Additional safety screens
More thorough reports add endotoxin testing (often the LAL assay described in USP <85>), microbial counts or sterility screens, and heavy metals. These are useful extras, not substitutes for identity and purity.
Methods, chromatograms and signatures
A strong COA states the methods and instruments, includes the chromatogram or mass spectrum, and is signed or digitally sealed by the analyst. Many labs also offer an online verification code.
How to verify a COA
Match the lot number on the COA to your vial, then check the report with the laboratory itself, using its verification portal or by contacting it directly. See how to verify third-party lab testing.
Example
Guardian Labs publishes each COA as a crawlable HTML record next to the original PDF, for example this Tesamorelin batch record. All records are listed on the Certificates of Analysis page.
Related guides
- How to Read a Peptide COA
- Identity Testing vs. Purity Testing
- Why Batch-Specific Testing Matters
- How to Verify Third-Party Lab Testing
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