Janoshik result on a Xi'an tirzepatide lot lands 1.1 points below the supplier’s figure

An independent purity determination on tirzepatide material sold by SWB has returned 97.8%, a figure 1.1 percentage points below the number printed on the accompanying certificate. The analysis was performed by Janoshik on a vial the Journal bought as an ordinary retail customer in April 2025 and posted unopened.

Content by elemental nitrogen determination returned 84% of the labelled nominal mass, which on a 20 mg vial corresponds to roughly 4.30 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.

Reported figures across the set were: highest 97.8%, lowest 94.6%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 13 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.

Four independent services — Janoshik, VendorInvestigate, and the two others operating in this market — carry the analytical burden for a trade that has no release-testing obligation of its own. Each is paid by whoever submits the sample, which is usually the vendor. The Journal’s position is that a submitter-pays model is workable but that its incentive structure has to be stated whenever a result is quoted as verification.

"The figure is not wrong and neither is theirs," said Rowena Ashcombe, community pharmacist and diabetes educator. "They are answers to two different questions and the trade has decided to pretend there is only one question. Print the gradient and the argument disappears."

SWB’s dossier has been updated with this determination and with the date of the request for comment. The dossier’s "what we could not verify" box records the questions still outstanding.