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Veriphase · Evidence

A label is a claim. Here is what measurement found.

Two independent bodies of evidence: the largest dataset yet published on gray-market peptides, and a smaller peer-reviewed study of semaglutide bought online. Both are set out with their limitations.

The largest dataset: 6,441 samples

Every figure this site quotes about failure rates comes from here. It is also the study with the most caveats, so both are set out below.

How many samples matched their label?

6,441 gray-market samples · 14 compounds · 203 synthesis companies

Passed the compounded-medication standard58.4%

Failed it41.6%

Failed the stricter manufactured-drug standard71.1%

0%50%100%

41.6% failed the compounded standard: measured amount 90–110% of the label claim, purity at least 98.0%, and the vial must contain the stated peptide. Held to the manufactured-drug standard — amount 95–105%, purity at least 99.5% — 71.1% fail.

Source: Mendias C, Awan T. 2026. Posted as a preprint on Preprints.org; not peer reviewed. doi:10.20944/preprints202604.1748.v1

The failure is almost never what people expect

Ask someone what goes wrong with a gray-market peptide and they will say it is the wrong compound, or that it is impure. Neither is the common answer.

Where the 41.6% actually fails

Compounded-medication standard · share of all 6,441 samples

Right peptide, acceptable purity, wrong amount in the vial32.8%

Failed both amount and purity3.3%

Right amount, purity too low3.0%

Did not contain the stated peptide at all2.4%

0%20%40%

32.8% of all samples were the right peptide, pure enough, and in the wrong quantity — ten times more common than an identity failure. Median purity across the whole dataset was 99.80%. Purity is rarely the problem. The milligrams are.

This is why every Veriphase certificate reports net peptide content as a separate number from purity. Why they are different measurements.

Per-compound figures

Compound	Passed both compounded	Passed both manufactured	Wrong peptide identity failure
Retatrutide	67.8%	47.0%	–
Ipamorelin	–	34.2%	–
CJC-1295	29.2%	10.7%	9.1%
TB-500	22.5%	7.5%	10.0%
Tirzepatide	–	13.8%	–
BPC-157	–	–	3.5%
All compounds	58.4%	28.9%	2.4%

Purity does not predict contamination

The two are measured separately because they are unrelated, and the data says so directly.

R² < 0.01 correlation between purity and bacterial endotoxin across the dataset (P = 0.75). A vial can be 99.9% pure and carry a meaningful endotoxin load. Why endotoxin needs its own test.

What this dataset does and does not show

It is a preprint and has not been peer reviewed. That is a real limitation. It has not been through the scrutiny that the smaller semaglutide studies below have, and its figures should be read with that in mind.

The sample is self-selected. These are vials that somebody chose to pay to have tested. People who already suspected a problem are over-represented, so the true failure rate across everything sold is probably lower than 41.6%. How much lower is unknown, and nobody can currently say.

It is not a random sample of the market. Compounds are represented unevenly — some by hundreds of vendor pairings, others by a handful — so per-compound figures carry very different weight from one another.

We benefit from this data being alarming. We sell testing. That is a conflict of interest, so the limitations belong here alongside the headline rather than only the headline.

A smaller study, under peer review

Three vials is not a market. But this one was published under peer review, and the method is the closest look available at what an unregulated supply chain delivers.

Purity against the label

Every vial was labelled 99% pure. Liquid chromatography–mass spectrometry measured what was actually there.

Semaglutide purity: claimed versus measured

3 vials · LC–MS · percentage of sample that was semaglutide

Stated on the label Measured in the laboratory

Label claim99%

Measured, across all three vials7.7% – 14.4%

0%50%100%

85–91 percentage points below what the label promised. Solid bar shows the lowest measured value; hatching spans the range to the highest.

Source: Ashraf AR, Mackey TK, Vida RG, et al. “Multifactor Quality and Safety Analysis of Semaglutide Products Sold by Online Sellers Without a Prescription.” Journal of Medical Internet Research, 2024. doi:10.2196/65440

View as table

Measure	Label claim	Measured range
Semaglutide purity	99%	7.7% – 14.37%
Total content vs label	100%	128.56% – 138.69%
Endotoxin	not stated	2.1645 – 8.9511 EU/mg
Viable microorganisms	—	none detected

More material than promised — and less drug

The same three vials contained more total substance than the label stated. Weight alone said the vials were generous. Only the purity measurement revealed what that weight actually was.

Total content versus actual semaglutide

3 vials · percentage of the labelled amount

Total material in the vial128.6% – 138.7%

Of which was semaglutide7.7% – 14.4%

0%100%200%

This is the gap between how much is in the vial and how much of it is the thing you wanted. Two different measurements, two different answers.

Same study. Content exceeded the labelled amount by 28.56%–38.69% while purity measured 7.7%–14.37%. A scale would have called these vials generous.

Contamination

Sterility and endotoxin are separate questions, and the answers went in opposite directions.

3 of 3

vials carried detectable bacterial endotoxin, at 2.16–8.95 EU/mg

0 of 3

vials contained viable microorganisms at the time of testing

59–63%

of packaging and labelling criteria failed visual inspection

What this study does and does not show

Three vials. That is a small sample, and we are not going to present it as more than it is. The value is in the method — the products were bought anonymously, then analyzed by LC–MS, sterility culture and endotoxin assay in a university laboratory, and published under peer review.

These were counterfeit prescription products bought from illegal online pharmacies selling without a prescription. That is an adjacent market to research peptides, not the same one. What the two share is the absence of anyone checking.

The sterility result went the other way. No viable microorganisms were found. We include that because leaving it out would be the kind of selective reporting this whole business exists to argue against.

A larger analysis of 26 follow-on semaglutide and liraglutide products in Pharmaceutical Research (2024, doi:10.1007/s11095-024-03771-6) reached compatible conclusions — novel impurities, trace metals, and several oral products containing markedly less semaglutide than the label claimed — though it reports impurity profiles rather than single headline percentages.