There is a market below the compounded one: vials shipped from websites with no prescription, no pharmacy license and, in several documented cases, no product. It is not the market the sellers reviewed here operate in, and the distinction is not always visible from a checkout page — which is the reason to read what a laboratory found rather than what anybody advertises. The supplier questions that separate the two are in the article on vetting a pharmacy.
What was ordered, and what arrived
One 2024 market surveillance study collected 1,080 links from search engine results pages. Of those, 317 (29.35%) belonged to online pharmacies, and 134 of the pharmacy links — 42.3% — led to 59 unique illegal online pharmacy websites. Traffic analytics for July to September 2023 showed the top 30 domains directly or indirectly affiliated with those operations accumulating over 4.7 million visits.[1]
Six test purchases were placed with the sellers offering products at the lowest prices. Three vials were delivered. The other three orders, all for prefilled pens, were never delivered at all: those sellers requested further payments ranging from $650 to $1,200 to purportedly clear customs, which customs agencies confirmed as fraudulent.[2] Half of the money spent bought nothing, before any question of chemistry arose.
The vendor characteristics were catalogued alongside the products. All six referred to weight loss or obesity on the product page. None required a prescription, and none assessed the buyer’s health status before taking the order; several advertised the absence of a prescription requirement as a feature. All six had already been classified as not recommended or rogue by an independent verification program, by a national pharmacy association, or by both — that classification was the inclusion criterion for the test buys.[2] The screening that caught them was public, and had been done before any of the money moved.
Purity and content point in opposite directions
Liquid chromatography coupled with mass spectrometry found semaglutide in all of the delivered samples. The measured content exceeded the labeled amount by 28.56% to 38.69%, which the accompanying research letter states as up to 39% more semaglutide per injection than the label promised.[1][2] On its own that reads like an accident in the buyer’s favor, and it is the half most likely to be quoted.
The other half is the one that matters. Measured purity ranged from 7.7% to 14.37%, against the 99% stated on the product labels.[1] Roughly seven-eighths of the material in those vials was something other than semaglutide, and while no peptide-like impurities were identified, the balance was not characterized. A vial can be simultaneously over-strength on the active ingredient and overwhelmingly composed of material nobody has named, and these were.
Sterile by culture, and carrying endotoxin
Microbiological testing found the lyophilized peptide samples devoid of viable microorganisms at the time of testing. Endotoxin was detected in all of them, at levels between 2.1645 and 8.9511 EU/mg.[1] The research letter records one sample at 8.95 EU/mg as indicating possible contamination.[2]
Those two results are not in tension. Endotoxin is a heat-stable fragment of a bacterial cell wall, so it persists after the organisms that produced it are gone; a culture that grows nothing establishes that no living organism is present, not that nothing pyrogenic is. It is the single clearest example of why a seller’s assurance that a product “tested sterile” answers a narrower question than it sounds like it answers. Handling after delivery raises a separate set of problems, covered in the storage article.
The packaging failed before the chemistry did
Both studies assessed the delivered products against the International Pharmaceutical Federation’s 22-point visual inspection checklist. A genuine reference product scored the full 22. The test-purchased products scored 8 or 9 out of 22, with clear discrepancies in regulatory registration information and labeling accuracy, and evidence that the products were likely unregistered or unlicensed.[2] Across the broader sample, visual inspection showed noncompliance in 59% to 63% of the evaluated criteria.[1]
The agency describes a related fraud on the compounded side of the line: products marketed in the United States carrying false information on the label, where the compounding pharmacy named on the label either does not exist or, on the information the agency has gathered, did not compound the product. One adverse event report is associated with a product labeled as compounded tirzepatide from a pharmacy that did not make it, involving redness, injection-site swelling, pain and a red lump.[3]
When the vial held a different drug entirely
The most consequential assay results are clinical. A 31-year-old woman was admitted in hypoglycemic coma after self-administering a semaglutide product obtained from a website; toxicological analysis showed the vial contained insulin rather than semaglutide.[4] Two further patients, neither with diabetes nor obesity, presented in coma with severe hypoglycemia, hypokalemia and hypothermia caused by synthetic insulin intoxication after injecting semaglutide obtained without a prescription; both required up to two days of continuous glucose infusion to stay euglycemic.[5]
The diagnostic point in the second report is worth stating plainly: semaglutide monotherapy is not associated with significant hypoglycemia in people without diabetes, so the presentation itself was the evidence that the product was not what the label said.[5] The World Health Organization had flagged the mechanism in June 2024, warning that falsified batches may contain an undeclared active ingredient such as insulin in the injection device, and noting falsified Ozempic detected in Brazil and the United Kingdom in October 2023 and in the United States in December 2023.[6]
What the safety databases record
A 2026 analysis retrieved individual case safety reports related to potential counterfeit semaglutide from the European pharmacovigilance database for 1 January 2018 to 31 December 2025. It found 234 reports, of which 172 (73.5%) concerned females, and 89.3% of the suspected reactions were serious. The most frequently reported were vomiting, nausea and hypoglycemia.[7]
The disproportionality analysis is where the pattern turns. Compared with non-counterfeit semaglutide, potential counterfeit product showed higher reporting of hypoglycemia, product use in an unapproved indication, malaise and drug ineffective.[7] Those last two signals are opposite failures sitting in one dataset: some product did something it should not have done, and some product did nothing at all. A page reporting only one of them would describe a coherent risk that the data does not support.
What these numbers are not
They are not a prevalence estimate. Three vials were delivered in the purchase study; the pharmacovigilance work counts reports of potential counterfeit product rather than confirmed ones, and its authors say further studies are warranted.[7] Nothing here supports a claim about what share of any market is falsified.
They are also dated. The search that produced the link sample ran in July 2023, the traffic window closed in September 2023, and the test purchases and analytical testing were carried out between August 2023 and March 2024.[1][2] That is a picture of the market while both drugs were still on the federal shortage list, and before the wind-down deadlines of 2025 closed the lawful route a large share of buyers had been using. No equivalent purchase study has been published since, so what the same sellers ship today is not a measured quantity.
Nor should the surrounding poison-center literature be read as a counterfeit signal. A national analysis of 10,033 GLP-1 exposures reported between 2012 and 2023 found most were unintentional therapeutic errors with mild gastrointestinal symptoms, while the proportion managed in or referred to a health care facility rose from 23.0% before the 2021 weight-loss approval to 33.5% after it, RR = 1.46 (95% CI 1.36 to 1.57, p < 0.001).[8] That measures system load across the whole drug class, not product falsification.
The agency’s own framing of the category is broader than counterfeiting and narrower than a finding: illegally marketed versions of these drugs may be counterfeit, may contain the wrong ingredients or harmful ingredients, or may contain too little, too much or no active ingredient at all.[3] It has also warned companies selling unapproved drugs containing semaglutide, tirzepatide, retatrutide, survodutide or mazdutide labeled “for research purposes” or “not for human consumption” while shipping them to consumers with dosing instructions.[3] What is known about the newest of those molecules is set out in the retatrutide article.
Where this sits next to a compounded prescription
A state-licensed pharmacy filling a prescription is a different object from a website shipping a vial to anyone with a card, and none of the findings above collapses that distinction. Compounded drugs are not FDA-approved and are not reviewed by the agency for safety, efficacy or quality before they are dispensed — and that is still a different statement from a laboratory reporting 7.7% purity. The regulatory ground under the lawful side of the line is in the shortage article, and what is physically in a lawfully compounded vial is in the article on vial contents.
What the assays do settle is the value of a low price as information. In the purchase study the products cost between $113 and $360 for the smallest quantity offered, a mean of $218.50 (SD $93.60), and half of those orders produced no product.[2] The checkout patterns that separate a pharmacy from a storefront are catalogued in the telehealth article.