Independent lab testing tells a consistent story: gray-market GLP-1 peptides routinely fail purity claims by catastrophic margins. Labeled at 99%. Measured as low as 7.7%. Every sample contaminated.
JMIR Dermatology (2024) purchased semaglutide from online gray-market sellers and submitted samples for independent HPLC analysis. The results were not close.
Source: JMIR Dermatology, 2024. HPLC purity analysis of semaglutide purchased from online vendors.
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Find Care →The same JMIR study tested all purchased samples for bacterial endotoxins -- the cell-wall fragments of gram-negative bacteria that trigger fever, sepsis, and organ failure when injected.
Every single sample tested positive for endotoxin contamination. One hundred percent. This is not a purity problem alone. It is a sterility failure at the most fundamental level.
Endotoxins are pyrogens -- they cause fever, inflammatory cascades, and septic shock even at microgram levels. They are not destroyed by autoclaving. They pass through standard 0.22μm sterile filters. Removing them requires dedicated depyrogenation steps that gray-market facilities rarely perform.
Novo Nordisk conducted independent testing of compounded semaglutide products obtained from US pharmacies. Their findings were submitted to the FDA and made public.
Amino acid analysis revealed additions and deletions in the peptide sequence -- the wrong amino acids in the wrong places. These are not inert errors. Missequenced peptides are immunogenic: the body recognizes them as foreign proteins and mounts an immune response, producing anti-drug antibodies that can neutralize both the compounded product and the FDA-approved medication.
One pharmacy's semaglutide product contained BPC-157 (Body Protection Compound-157), a research peptide with no FDA approval for any indication. Patients injecting what they believed was semaglutide were unknowingly administering an unapproved substance with no established safety profile in humans.
Most compounding pharmacies use semaglutide sodium or tirzepatide sodium as their starting material. The FDA-approved drugs use semaglutide base and tirzepatide base. These are different molecules.
The FDA has stated explicitly that semaglutide sodium and tirzepatide sodium have "not been shown to be safe and effective" and that there is "no legal basis" for compounding them for human use. The salt forms alter the pharmacokinetic profile -- how the drug is absorbed, distributed, and eliminated -- in ways that have never been studied in clinical trials.
This is not a technicality. The salt form changes molecular weight, solubility, stability, and bioavailability. Every clinical trial that established the safety and efficacy of semaglutide and tirzepatide used the base form. The salt form is, from a regulatory and pharmacological perspective, a different drug entirely.
FDA-approved GLP-1s are manufactured in ISO-certified cleanrooms with continuous environmental monitoring. Gray-market peptides are reconstituted on kitchen counters, guided by Reddit threads.
Janoshik Analytical, the most widely used third-party testing lab in the peptide community, published aggregate data from their 2024 testing volume. The numbers are unambiguous.
Finnrick Labs tested 2,446 samples of retatrutide -- a next-generation GLP-1 agonist gaining rapid adoption in gray markets before any FDA approval. Their findings: quantity diverged up to ±46% from label claims, and 10% of samples failed sterility, purity, or dosing thresholds.
A ±46% dosing variance means a patient expecting 5mg could receive anywhere from 2.7mg to 7.3mg. At the high end, this exceeds the dose escalation protocols that clinical trials use to minimize gastrointestinal side effects. At the low end, the patient is undertreated and may conclude the medication does not work.
Shipped semaglutide at 79.9% labeled potency. Separately distributed tirzepatide that had failed sterility testing. In both cases, zero patient notification was issued. Patients injected sub-potent and potentially contaminated product without knowledge.
Sold vials labeled as semaglutide that actually contained cagrilintide -- a completely different peptide with different receptor binding, different pharmacokinetics, and different side effect profiles. Customers had no way to know without third-party testing.
Distributed Certificates of Analysis (COAs) bearing the Janoshik Analytical name and logo that Janoshik confirmed were fabricated. Customers who trusted the COA as proof of quality were relying on a forged document.
Counterfeit Ozempic pens entered the US supply chain containing insulin glargine instead of semaglutide. Three patients were hospitalized for hypoglycemia -- dangerously low blood sugar caused by an insulin they did not know they were injecting.
The 7.7% purity figure isn’t a one-off outlier. It’s the visible end of a pattern documented across multiple independent testing operations and peer-reviewed studies.
43% of peptides tested by Janoshik Analytical in 2024 failed to meet their label purity claims. Lower-tier vendors averaged 71–91% actual against advertised 99%+. Janoshik Analytical 2024 aggregate, Peptide Protocol Wiki review
73% of 1,200+ samples tested by ACS Peptide Labs (2024–2026) showed purity discrepancies versus the supplier’s COA. Average shortfall: 8.4 percentage points below claimed. 41% of samples were off by more than 10 points. ACS Peptide Labs 2024–2026 dataset
34% of repeat customers find different purities batch-to-batch from the same vendor. The vial that worked last month isn’t the same molecule you’re injecting today. ACS Peptide Labs repeat-customer data
±45% quantity variance from advertised vial amounts is the normal range across 6,937 samples in the Finnrick Analytics database (205 vendors, 15 peptides, Dec 2024 – Apr 2026). A vial labeled “5mg semaglutide” routinely contains anywhere from 2.75mg to 7.25mg. Finnrick Analytics 2024–2026, finnrick.com
The community talks about “testing every batch” like it’s the standard. The data says otherwise.
Independent testing runs $50–$300 per sample depending on the lab and panel. A full Janoshik blind GLP-1 test is $828. For a user spending $40 on a vial of “sema,” sending it off costs more than the product itself. So they don’t.
Janoshik, MZ Biolabs, Chromate published pricing
The most common pattern on glp1forum.com isn’t personal testing. It’s users relying on a screenshot of someone else’s result from a different batch, weeks or months earlier. One forum quote: “I didn’t [test]. Used for a couple of weeks first.” Single-vial vendors make personal testing structurally impossible — you’d be sacrificing your only vial.
glp1forum.com vendor & testing threads
Of products submitted to Janoshik for testing — a sample biased toward users who care enough to test — roughly 5% test as the wrong compound or degraded entirely and another 3–5% fail sterility. The unbiased market rate is almost certainly higher.
Samples sold as semaglutide tested as cagrilintide — a different peptide entirely, with different mechanism, different dosing, different safety profile. Confirmed by three independent labs (Janoshik, MZ Biolabs, TrustPointe). Anyone dosing “sema” from this vendor was injecting an amylin analog without knowing it.
Peptide Protocol Wiki, Janoshik Analytical Review
One vendor’s “semaglutide” came back with a molecular weight of 2,847 daltons. Real semaglutide is 4,113 daltons. The reviewing chemist’s assessment: “not semaglutide at any purity level.” An entirely different molecule, sold under semaglutide’s name.
Peptide Protocol Wiki, mass-spec analysis
SS31 vials labeled 50mg actually contained 44.10mg (11.8% short). Endotoxin tested at 26.79 EU/vial — above the lab’s validated reporting range, meaning the actual level was higher than the test could measure. The company offered “future credits” instead of refunds and banned customers who reported issues publicly.
glp1forum.com testing threads, Graymarket Substack investigation
A premium-priced primo-E product tested as testosterone propionate — a much cheaper compound. The community-vouched “gold standard” selling a different drug at a markup. Peptide Sciences shut down March 2026 after a federal raid.
Peptide Protocol Wiki, Janoshik Analytical aggregate
A peer-reviewed study (PMC 11582493) bought semaglutide from three illegal online pharmacies marketed to consumers and ran complete pharmaceutical analysis. The labels claimed 99% purity. Here’s what was actually in the vials.
| Vendor | Claimed Purity | Actual Purity | Excess Active | Endotoxin (EU/mg) | Quality Criteria Met |
|---|---|---|---|---|---|
| SemaSpace | 99% | 14.37% | +28.56% to +38.69% | 8.95 | 9 / 22 (41%) |
| USChemLabs | 99% | 8.97% | +28.56% to +38.69% | <2.16 | 8 / 22 (36%) |
| BiotechPeptides | 99% | 7.7% | +28.56% to +38.69% | <2.87 | 8 / 22 (36%) |
Two things to absorb from that table. First: every vendor measured at less than 15% actual purity against a 99% claim. Second: every vendor also overdosed the labeled active by 28–39% — meaning users who titrated dosing based on the label were getting a wildly inaccurate amount, in either direction. Endotoxin (bacterial cell-wall fragments that cause septic shock and injection-site reactions) was present in all three.
Source: Multifactor quality analysis of semaglutide from illegal online pharmacies, PMC 11582493 (2024)
The bonus finding: 50% of the test purchases (3 of 6 vendors approached) turned out to be straight nondelivery scams. Fake courier companies demanded $650–$1,200 in “customs fees” before product shipment, then disappeared with the money. Buyers who avoid the contamination still lose to fraud at a measurable rate.
This page aggregates purity data from peer-reviewed research, FDA enforcement records, manufacturer testing reports, and independent analytical laboratories. Primary sources include:
Know Your Vial has no financial relationship with Novo Nordisk, Eli Lilly, or any pharmaceutical manufacturer. We do not sell peptides, supplements, or testing services.
A standard $300 Janoshik test covers identity and quantity. It misses the 7 things that send people to the ER.
43% of peptides tested by Janoshik failed purity claims. Modern Peptides forged lab certificates entirely.
At least 10 deaths, over 100 hospitalizations, and a 1,500% increase in poison control calls.