How to evaluate a peptide vendor
A practical checklist for assessing quality, purity, and legitimacy of peptide suppliers — third-party testing, COAs, reconstitution guidance, and red flags.
Updated 2026-04-20
The five checks
- Independent third-party testing. Reputable vendors publish certificates of analysis (COA) for every batch from an accredited lab (not the manufacturer). Look for HPLC purity data and mass spectrometry identity confirmation.
- Batch-level COAs. A single historical COA is marketing. A current COA that matches the batch number on your vial is evidence.
- Realistic pricing. Suspiciously cheap peptides are either underdosed, impure, or not what they claim to be.
- Clear regulatory framing. Legitimate research-chemical vendors are explicit about "research use only". Vendors aggressively marketing for human consumption are the ones most likely to cut corners.
- Reconstitution and storage guidance. A vendor that provides dosing calculators, bacteriostatic water pairing, and storage instructions is a vendor that expects scrutiny.
Red flags
- No COA or a COA that can't be matched to a batch number
- Dramatic before/after photos in marketing
- Medical claims ("cures", "treats", "prevents")
- Payment only in crypto with no order tracking
- Domain less than 12 months old with no trading history
What a good COA contains
- Compound identity (mass spec, sequence)
- Purity (HPLC, typically >97%)
- Residual solvents
- Endotoxin levels (for injectables)
- Batch/lot number and date
Storage 101
Most peptides are shipped lyophilised (freeze-dried). Store unreconstituted vials at 2–8 °C. Once reconstituted with bacteriostatic water, most peptides are stable at 2–8 °C for 28 days.