What a COA is for
A Certificate of Analysis (COA) is a lab report tied to a specific manufactured batch of a compound. It's meant to answer two separate questions: is this actually the substance the label says it is (identity), and how pure is it (purity, usually via HPLC or mass spectrometry)?
A trustworthy COA names the testing lab, references a specific batch or lot number, and includes the actual chromatogram or numeric results — not just a purity percentage printed on a product page with no source.
The gap between 'tested' and 'verified'
Almost every vendor's marketing copy says something is tested or lab-verified. Far fewer actually link to a report you can check yourself. On PeptideCompare we split this into three tiers — Verified COA, Claimed (unverified), and No documentation — specifically because the marketing language tends to blur this distinction. See our methodology page for exactly how each tier is defined.
A batch-specific COA (tied to the exact lot you'd receive) is stronger evidence than a generic 'representative' COA the vendor reuses across batches — but a generic COA from a named, reputable lab is still meaningfully better than an unverified claim.
Red flags worth noticing
No lab name anywhere, only a purity number. A COA image that's clearly a screenshot with no batch number visible. A 'testing partner' that doesn't have any public presence you can independently confirm. Any of these should lower your confidence, even if the price looks attractive.
Price and verification often move in opposite directions — the cheapest listing for a given peptide is frequently the least documented one. That doesn't automatically make it wrong, but it's a reason to look closer rather than assume the lowest number is the best deal.
For research use only. This guide is general background information, not medical or dosing advice.