Peptide Quality & COA Guide

Why purity matters#

Peptide quality varies enormously across the research chemical market. An underdosed peptide means you're not getting the effect you're dosing for. A contaminated peptide — whether with bacterial endotoxins, solvents, or misidentified compounds — can cause reactions ranging from inflammation to serious illness. Purity isn't a luxury consideration; it's the baseline for safe use.

What a COA is#

A Certificate of Analysis (COA) is a document from a testing laboratory that verifies what is in a product. For peptides, a legitimate COA should include: identity confirmation (is this actually the peptide claimed?), purity percentage by HPLC (High-Performance Liquid Chromatography), and ideally mass spectrometry (MS) to confirm molecular weight matches the expected compound. The testing lab should be independent — not the vendor's in-house lab.

What to look for in a COA#

Target purity: 98%+ is considered high quality; 95–97% is acceptable; below 95% is substandard for injectable use. Check the test date — a COA from 3 years ago may not reflect the current batch. Look for the peptide's sequence or molecular formula to confirm identity. The lab name should be searchable and verifiable. Batch numbers on the COA should match the batch number on your vial.

Red flags to watch for#

Be wary of: COAs with no lab name or an unverifiable lab, purity listed as a round number with no decimal (e.g. exactly '99%' with no variance), COAs that cover a product category rather than a specific batch, vendors who refuse to share COAs or make them difficult to find, and unusually low prices — quality peptide synthesis is not cheap.

Some vendors publish COAs on their websites by lot number. Always verify the lot number matches what's on your vial.

Third-party community testing#

Independent community testing projects (such as those run by harm reduction communities) purchase peptides from vendors and submit them to accredited labs. These results are published publicly and are often more trustworthy than vendor-provided COAs. Checking community testing databases before purchasing from an unfamiliar vendor is one of the most reliable quality checks available.