Choosing a supplier

How to evaluate a research-peptide supplier: certificates, testing, and the claims a careful buyer should check.

• Peptide Sciences shut down: how to choose an alternativePeptide Sciences, a widely used US research-peptide supplier, closed in early March 2026. Its own notice says it chose to "voluntarily shut down operations"; no public source confirms why. If you are choosing a replacement, check each lot's certificate of analysis, who issued it, and what it actually tests.
• How to vet a peptide supplier: a 10-point checklistVet a research peptide supplier on its documents and its conduct: a certificate for each lot, naming the laboratory and who issued it; measured figures for both purity and identity; a lot you can match to your vial; honest gaps and public corrections; and research-use framing, policies and a business identity that agree everywhere.
• Red flags in a peptide COA: spotting a fakeDoubt a peptide certificate of analysis when its lot is missing or doesn't match your vial, its laboratory can't be found, its purity is a round minimum, its chromatogram is missing or cropped, its formula disagrees with its own molecular weight, or the lab can't confirm it. One flag is a question; several are a pattern.