Independent analysis puts a Homopeptide retatrutide lot at 98.9%, against 98.1% on the certificate

An independent purity determination on retatrutide material sold by Homopeptide has returned 98.9%, a figure 3.9 percentage points above the number printed on the accompanying certificate, which the supplier had reported against a shorter gradient and a tighter threshold. The analysis was performed by Medutest on a vial the Journal bought as an ordinary retail customer in May 2025 and posted unopened.

Content by elemental nitrogen determination returned 95% of the labelled nominal mass, which on a 30 mg vial corresponds to roughly 12.02 mg of peptide rather than the labelled figure. The remainder is accounted for by counter-ion, residual water and residual solvent, none of which is visible chromatographically.

Batch variance rather than vendor quality is the recurring finding of this programme. Across the 22 determinations the Journal has commissioned to date, within-vendor spread has been wider than between-vendor spread for two thirds of the companies tracked, which is an argument against rating any supplier on a single number.

Dr Sirichai Boonmee, peptide chemist, Chulalongkorn University, wanted the wavelength printed. "A method reading at 280 nanometres cannot see a fragment that has lost its aromatic residue. That is not a failure of the laboratory, it is a fact about the question they were asked."

Homopeptide’s dossier has been updated with this determination and with the company’s response to it. The dossier’s ordering box records the lead times, the minimum quantities and what a buyer should ask for at the point of order.