Medutest result on a Tianjin semaglutide lot lands 2.4 points above the supplier’s stated figure

Medutest has published a purity determination of 95.3% on a 2 mg vial of semaglutide supplied by TFC, against a figure of 93.9% on the certificate that accompanied the vial. The sample was submitted by the Journal in April 2025 as part of a continuing programme of arm’s-length purchasing, and the vendor was told before the order was placed that any result would be published.

Reported figures across the set were: highest 95.3%, lowest 93.9%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 5 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.

Reported figures across the set were: highest 95.3%, lowest 93.9%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 5 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.

Discrepancies of one to two percentage points between a supplier’s figure and an independent determination are common and usually explicable: a faster gradient resolves fewer impurities, a higher integration threshold discards more small peaks, and a wider solvent-front exclusion window removes early-eluting fragments from the calculation altogether. None of that is misconduct. All of it is invisible unless the method is disclosed.

"The gap that matters is not between the two laboratories, it is between either of them and the certificate," said Dr Sirichai Boonmee, peptide chemist, Chulalongkorn University. "One of those documents states a method. Compare like with like and most of this disappears."

TFC’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.