Methodology

How we rank UK research peptide retailers

Every UK research peptide retailer listed on PeptideClear has passed the same 8-criteria assessment. This page documents the criteria, the weighting, and the periodic refresh cadence so readers can interrogate the editorial judgement behind any retailer ranking.

Inclusion criteria (mandatory floor)

• · UK-shipping operator with at least 12 months of trading history.
• · HPLC purity claim with stated percentage (typically 99%+).
• · Either Certificate of Analysis (CoA) provided on order or available on request.
• · Marketed under "research use only, not for human or animal consumption" framing on every product page.
• · No therapeutic health claims about the peptides in marketing copy.
• · Trading entity identifiable (registered UK company or named operator).
• · Functional customer service contact within UK business hours.

Retailers failing any one of these are not listed. We do not list grey-market suppliers, importers operating without UK trading entity, or any retailer making therapeutic claims about research peptides (which would put them in scope of the Human Medicines Regulations 2012).

Ranking criteria (weighted)

• HPLC purity transparency (25%): declared percentage, third-party lab named, mass spectrometry available alongside HPLC.
• CoA provision (20%): provided with order > available on request > only published examples.
• UK delivery (15%): UK warehouse > UK + EU distribution > international shipping with UK customs.
• Payment flexibility (10%): card + Apple Pay + Google Pay + bank > card only > crypto only.
• Customer service responsiveness (10%): reply within 24 hours to purity or product questions during weekdays.
• Trading history (10%): longer UK trading history scores higher.
• Site UX and documentation (5%): clear research-use-only framing, accessible CoAs, no health claims.
• Range breadth (5%): wider catalogue scores higher when other criteria are tied.

What we explicitly do not measure

• · Biological activity of the peptide (HPLC purity does not prove activity).
• · Sterility (a separate analytical test, rarely provided by research peptide retailers).
• · Dose accuracy (a separate analytical test).
• · Customer outcomes (we do not solicit or publish user health outcomes from research peptide use).

Refresh cadence

Retailer rankings are reviewed every 90 days. Any of the following triggers an immediate re-review: change in trading entity, change in HPLC purity claim, removal of CoA provision, addition of therapeutic claims, change in UK delivery model, customer complaint volume above threshold.

Conflict of interest

Some retailers run affiliate programmes that PeptideClear participates in. Affiliate participation does not lift a retailer in the ranking. Two ranked retailers in 2026 do not run affiliate programmes; they are ranked on the same criteria as those that do.

Related: full UK retailer comparison · editorial policy · how we are funded.