Sourcing
How to evaluate a peptide seller
Independent analyses of consumer-purchased research peptides repeatedly find under-dosed vials, wrong or degraded sequences, and endotoxin contamination. The variable that separates credible suppliers from the rest is verifiable third-party testing at the lot level — not website design, not price, and not review volume.
What a credible supplier provides
- Lot-specific certificate of analysis that matches the vial you received
- HPLC purity plus mass-spectrometry identity confirmation, not purity alone
- Named, independently verifiable third-party testing laboratory
- Endotoxin (LAL) testing for anything intended as an injectable preparation
- Clear research-use-only labeling with no human dosing instructions
- Cold-chain shipping and documented storage conditions
Red flags
- One COA reused across every product or every lot
- Human dosing protocols, 'cycles', or before-and-after photos in marketing
- Claims of FDA approval, 'pharmaceutical grade', or 'clinically proven' for research peptides
- No batch numbers on vials
- Prices far below the market for a compound that is expensive to synthesize
- Testimonials describing personal use as the primary evidence
Reading a certificate of analysis
A COA is only meaningful if it can be tied to the specific vial in your hand. Check that the lot number on the document matches the label, that the testing date postdates synthesis, and that the laboratory is named with contact details you can independently verify.
Purity by HPLC tells you what fraction of the material is a single peak. It does not tell you that the peak is the peptide you ordered. Mass spectrometry confirms molecular weight and is the identity check that catches wrong or truncated sequences.
For anything reconstituted and injected in a research setting, endotoxin testing matters more than marginal purity differences. A 99% pure peptide with bacterial endotoxin is a worse product than a 97% pure one without it.
Legality comes before sourcing
In most jurisdictions, peptides that are not FDA- or regulator-approved have no lawful route to human use, and several countries treat importation as a criminal matter rather than a regulatory one. Check your state or country status before evaluating any supplier.