What is a peptide COA? The document behind every serious peptide order

A peptide COA — Certificate of Analysis — is a laboratory report for one specific batch of one specific peptide. It records what a lab measured when it tested that batch: the identity of the molecule, how pure it is, and how much actual peptide is in the vial.

Two things in that definition matter more than anything else on the page:

• It is a measurement, not a promise. A COA reports instrument output — a mass spectrometer reading, a chromatogram, a titration. It is evidence, where a product label is a claim.
• It covers one batch only. The lot number on the COA is the anchor. If it doesn't match the lot on your vial, the document says nothing about what you're holding.

Everything else — the letterhead, the logo, the confident formatting — is presentation. The numbers and the lot number are the document.

A COA can run to several pages, but four results carry almost all of the weight:

1. Identity (LC-MS). The observed mass of the molecule next to the theoretical mass calculated from the sequence, with a small deviation. "Confirmed" with no numbers is a claim, not a result.
2. Purity (HPLC). The percentage of the UV peak area that is the main peak — with the method stated (column, mobile phase, gradient, wavelength). A purity number without a method is not reproducible.
3. Content (assay). How many milligrams of actual peptide are in the vial. Lyophilized peptides carry water and counter-ion, so a "5 mg" vial often contains 3.8–4.5 mg of active peptide. Purity alone never answers this.
4. Endotoxin (injectable-grade only). A numeric value in EU with the method (LAL or rFC) named. Not required for research-grade material — required for anything entering a living system.

A COA missing any of the first three is incomplete. For the full walkthrough — including counter-ion, water content, and residual solvents — see our line-by-line guide to reading a peptide COA.

There are two kinds of peptide COA, and they are not equal:

• A vendor COA is issued by the manufacturer or seller. The methods may be perfectly sound — but the entity reporting the result is the same entity that profits from it.
• An independent (third-party) COA comes from a lab with no commercial stake in the sale. Same instruments, same methods — different incentives.

This is the entire argument for third-party peptide testing, and it's why "tested" on a product page is meaningless until you know who did the testing. More on that in why third-party peptide testing matters and how to tell if your peptide is actually third-party tested.

Most bad COAs aren't elaborate forgeries. They're real documents reused for the wrong batch, or templates with edited numbers. The warning signs take minutes to check: the same COA across multiple products, suspiciously perfect numbers on every batch, a lab you can't find or contact, a molecular weight that doesn't match the sequence, or no way to verify the document with the issuing lab.

The single strongest defence is a verification route hosted by the lab, not the seller — a URL, QR code, or report number that shows the record the lab actually holds. We cover the full checklist in the fake COA section of the reading guide.

Knowing what a COA is gets you past the marketing. Knowing how to read one gets you past the document itself. Our main guide walks through a peptide COA section by section — header, identity, purity, content, supporting data, endotoxin, signature — with a five-minute pre-order check you can run on any vendor's document:

How to read a peptide COA (and spot a fake) before you order →

And if you want a vial tested rather than a document checked, the cost guides for BPC-157, TB-500, semaglutide, and retatrutide break down what a complete verification costs, item by item.