The fields that actually matter
A certificate of analysis exists to prove what’s in a specific vial. That means the useful information is specific, not generic: a batch or lot number that matches the vial’s own label, a test date, the name of the lab that ran the test, and a purity percentage from an actual method like HPLC (high-performance liquid chromatography).
Batch numbers are the anchor
Without a batch number tying the COA to the exact vial being sold, the document proves nothing about that specific purchase. It could describe a different, better batch entirely. A trustworthy listing makes it easy to check that the COA’s batch number matches what’s printed on the vial received.
What a weak or fake COA looks like
Watch for COAs with no lab name, a lab name that can’t be found or verified independently, purity numbers with no stated test method, or a test date far in the past relative to when the batch was supposedly made. A document that’s clearly a template with only the product name swapped between listings is a strong warning sign.
Independent lab testing
Some UK buyers send a sample of a purchased peptide to an independent lab for their own verification, separate from whatever the supplier provided. This is more common for higher-value or first-time orders and isn’t necessary for every purchase, but it’s the most reliable way to confirm a supplier’s own documentation is accurate.
Using a COA correctly
Cross-check the COA against the physical vial: batch number, stated mg content, and expiry or manufacture date should all agree. A COA that doesn’t match the vial in hand is a reason to contact the supplier before use, not to assume it’s a minor paperwork mismatch.