The best UK research-peptide vendors: independently tested

Of the 521 active UK research-peptide retailers we audit, only 41 (8%) publish their own verifiable Janoshik certificate of analysis, a report that names the vendor itself as the client and can be checked on Janoshik's own website. Ranked below by most recent certificate.

Looking for one peptide? See which verified sellers hold a certificate for each compound, newest first.

What "best" means here: this is not an endorsement, and we take no payment from any vendor. It is the list of sellers whose testing you can actually verify. Everything else is on the watch list. And remember, even a verifiable COA proves a sample was tested, not that your vial matches it, see what this can and can't tell you.

New to reading certificates? Start with how to verify a Janoshik COA, or upload one to the COA Checker.

The same question from other angles: the best UK peptide supplier, ranked by verifiable certificate, the best peptide company in the UK, the most trusted UK peptide suppliers, four signals you can check, where to buy peptides in the UK, the checklist and the sellers that pass.