Why this matters, with real numbers

A 2024 study in the Journal of Medical Internet Research (Ashraf, Mackey and colleagues) bought semaglutide products from online sellers without a prescription. Three vials arrived, and all three were judged probable substandard or falsified. Measured semaglutide purity was 7.7% to 14.4%, against 99% claimed. Content was 28.6% to 38.7% over the labeled amount. Endotoxin was detected in every sample. The three Ozempic pens the researchers ordered never arrived. It is a small sample from one product category, so it shows what can go wrong, not how often.

The Victoria (Australia) Department of Health issued an alert on June 19, 2026 about six cases of acute liver toxicity since January 2026 linked to an unapproved product labeled as retatrutide. Contamination was suspected. The FDA’s page on unapproved GLP-1 drugs, updated October 1, 2026, reports dosing-error adverse events, some needing hospitalization.

The lines on a COA, in plain words

Purity is not content

This is the most common misunderstanding. A synthetic peptide is usually made as a salt. Trifluoroacetic acid (TFA) is the main counterion in peptides made by common solid-phase synthesis, according to a 2025 consensus paper in Pharmaceuticals. A GenScript technical presentation says delivered peptide samples are typically only 50% to 80% target peptide by weight, with TFA often 10% to 30% of the weight and water usually under 10%. Another supplier, AmbioPharm, shows the arithmetic for theoretical net content and says actual values are measured by methods like amino acid analysis or elemental analysis.

So a “99% pure” vial can still contain well under the labeled weight of actual peptide. The practical question is whether the label amount refers to total powder or to net peptide. The COA should say, and if it does not, that is a gap. These are supplier technical documents, not regulations.

Sterility and endotoxin are different tests

USP General Chapter <71> covers sterility testing and USP <85> covers the bacterial endotoxins test. They are separate chapters because they answer separate questions. A purity chromatogram does not show either one. If a COA lists only purity and mass, it says nothing about sterility or endotoxin. The USP chapter texts are behind a subscription, so we link to their official listings only.

Whose COA is it?

Under US drug manufacturing rules (21 CFR 211.84), a drug maker may accept a supplier’s report of analysis only if it also runs at least one identity test itself and validates the supplier’s results at appropriate intervals. The principle is simple: do not rely on the seller’s own paper alone. For a buyer, that points to some checks:

• Is the lab independent of the seller?
• Does the report carry a batch or lot number, and does it match the label on the vial?
• Can you verify the report on the lab’s own site, rather than only as a PDF the seller sent?
• Does it include a date and the test method?

Even a perfect report covers the sample that was tested. It does not prove the vial in your hand came from that batch. Our reasoning

Common questions

Keep reading

• What lyophilized means, and what looks wrongThe freeze-dried cake, and what to check after mixing.
• How to store peptidesWhat approved labels say, and where the guidance stops.
• mg, mcg, IU and syringe units explainedmg, mcg, IU and syringe units. They are not interchangeable.
• Bacteriostatic water vs sterile waterWhat is in each bottle and what the labels say.

Educational reference, not medical advice. This page describes what public health and regulatory sources say. It does not tell you what to take or do.