How to Read a
Peptide COA —
And Why Most Physicians Don't

Every peptide that leaves a legitimate manufacturing facility ships with a Certificate of Analysis. Most physicians file it, or ignore it entirely. A significant number have never looked at one closely enough to know whether it actually confirms what it claims to confirm.

This is not a criticism. Medical training does not include pharmaceutical analytical chemistry. But if you are prescribing compounded injectables, understanding what a COA tells you — and what it does not — is part of responsible clinical practice. This article walks through every section.

What a COA is — and what it isn't

A Certificate of Analysis is a document produced by a testing laboratory that summarizes the analytical results for a specific lot of a compound. It confirms that the laboratory tested that lot and that the results fell within acceptable specifications.

What it is not: a guarantee that the compound is safe for research use, a regulatory approval, or a substitute for USP-797 certified manufacturing conditions. A COA tells you what was in the vial when the laboratory tested it. It does not tell you how the compound was made, under what conditions it was stored, or whether the lot you received is the same one that was tested.

Reading the header: what to verify first

The top section of any COA contains the basic lot identification information. Check these fields carefully:

• Client name: Should match the manufacturing facility or distributor you ordered from — not a third party you don't recognize
• Laboratory name and address: This is the testing lab — confirm it is a named, independent third-party laboratory with a verifiable physical address and website
• Sample name / Product: Should match the compound you ordered (e.g., "Semaglutide 30mg" or "GLP-1 (S) 30mg") and the lot number should match your shipment documentation
• Published / Analysis date: Should be recent relative to your shipment — a COA dated months before your order may indicate the lot has been sitting in storage or that documentation is not lot-specific

The results section: the three numbers that matter

Most COAs for compounded peptides report on three core parameters. Each one tells you something different:

1. Identity (ID by RT / ID by Spectral)

This confirms that the compound in the vial is actually what it is labeled as. Testing methods include Retention Time (RT) comparison against a reference standard or spectral analysis (mass spectrometry or UV). A result of "1.00" or "1000" in these fields typically means the sample matched the reference standard — confirming identity. A result that does not match, or a COA that omits identity testing entirely, is a serious red flag.

2. Purity

Purity measures the percentage of the compound that is the intended molecule, versus impurities or degradation products. For compounded GLP peptides, acceptable purity is typically above 98%, with high-quality lots ranging from 99.75% to 99.85%. A purity result below 98% warrants a direct conversation with your supplier about that specific lot.

3. Assay (Quantity)

The assay confirms the actual mass of the active compound in the sample. If you ordered a 30mg vial of Semaglutide, the assay should confirm approximately 30mg of active compound — though some variation above nominal is common due to overfill practices. The Chromate COA format, for example, shows both the specified quantity and the actual result with a percentage difference. A significant underfill warrants attention.

The approvals section: who signed it

A COA should be signed by identified personnel at the testing laboratory — typically a President, Managing Director, or Principal Chemist by name and title. Anonymous or unsigned COAs are not acceptable documentation. The person signing is attesting to the accuracy of the results.

The verification mechanism: the most important feature

The single most important feature of a COA from a credible laboratory is an independent verification mechanism — a QR code, URL, or access key that allows you to confirm the COA results directly at the issuing laboratory's database, without going through the supplier.

This matters because a COA without independent verification can be altered. A document is only as trustworthy as the party who gave it to you. When the COA contains a QR code that links to the laboratory's own portal, and that portal shows the same results, you have independent confirmation that the document has not been modified.

Red flags at a glance

• No identity testing — purity alone is not enough; the compound must be confirmed to be what it is labeled
• Self-issued COA — if the lab name matches the supplier name, that is not independent testing
• No verification mechanism — a COA with no QR code, URL, or access key cannot be independently confirmed
• Purity below 98% — warrants direct discussion; anything below 95% should be refused
• Generic or undated lot numbers — COA should be lot-specific and dated within a reasonable window of your shipment
• Missing signatory — unsigned or anonymously signed COAs are not credible documentation

The bottom line

Reading a COA is a five-minute task that takes less time than reading this article. Adding it to your receiving workflow, confirming identity, purity, and lot-specific verification, is the simplest quality control step a prescribing physician can take.

If your current supplier's COAs do not include a verifiable third-party testing mechanism, that is worth raising directly. If they cannot provide one, that tells you what you need to know.