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Grey-Market Encyclopedia · Physical risks

Physical risks of grey-market peptides

What is actually in the vial, and what can happen after it is injected. This page draws only on published product tests, regulators' statements and case reports, and says where the evidence runs out.

Last updated October 28, 2026 · Reviewed by Grey Peptides Editorial Board · ✓ Every claim sourced · No products sold, no seller named

📋 Key takeaways

Published tests of grey-market products have found the right molecule in the wrong amount, in both directions: semaglutide vials held 29% to 39% more than their labels,1 and three products sold as retatrutide held about half, nearly double and two-thirds more than labelled.2

They have also found the wrong molecule or none: 8 of 17 products sold as follistatin 344 contained no protein of its size,4 and none of 14 products sold as ACE-031 contained it.5

Endotoxin, a fever-causing bacterial residue that sterilizing filters do not remove,7 was measured in one of three tested semaglutide vials.1 Injection-site reactions are among the effects reported with unregulated peptides,14 and case reports describe hospital care after unsupervised use of online products.1718

On this page

  1. What the evidence is
  2. The wrong compound, or none
  3. The wrong amount
  4. Contamination and impurities
  5. Endotoxin
  6. Sterility
  7. Heavy metals
  8. Injection reactions and infection
  9. Harm from unsupervised use
  10. What testing can and cannot settle
  11. Frequently asked questions
  12. Related on Grey Peptides
  13. Sources

What the evidence is

The physical risks of a grey-market product come from two places: what is in the vial, and how it is used. Evidence on the first comes from laboratories that bought or received products and tested them; evidence on the second comes from regulators' adverse-event data and case reports written by clinicians. Neither kind is a census. A test covers the vials tested, and a case report describes one patient, so neither says how often a problem occurs across the market (our reasoning). They show what can be in a vial and what has happened to people.

Our published test results page collects every product test we have found, with the laboratory, method, date and source, failures included. The findings below are taken from the papers behind it.

The wrong compound, or none

The plainest failure is a vial that does not contain what it is sold as. Three published studies of black-market protein products found this:

  • Follistatin 344. A doping-control laboratory bought 17 products sold as follistatin 344 from internet suppliers. Eight contained no protein larger than 20 kDa on gel electrophoresis, so no follistatin; mass spectrometry found small growth-promoting peptides in some of these instead.4
  • ACE-031. The same group bought 14 products sold as ACE-031, an activin receptor fused to an antibody fragment. Twelve contained the receptor without the antibody fragment, one contained follistatin 344 instead, and one contained no protein.5
  • Seized injectables in Europe. A coordinated week of seizures across 12 European countries in 2014 found laboratories reporting growth hormone, sermorelin and melanotan II among falsified injectables, and products with no active ingredient.6

Smaller peptides have mostly been found to be what their labels say. Identity was confirmed in products sold as retatrutide,2 melanotan II,3 semaglutide1 and BPC-157.19 Identity is not the whole question, though, as the next section shows.

The wrong amount

A vial can hold the right molecule and still the wrong amount, which matters because a buyer measures a dose by the label (our reasoning):

  • Semaglutide. A Hungarian study team bought semaglutide from online sellers without a prescription and measured three vials: each held 29% to 39% more semaglutide than its label stated. The same method read a genuine pen at 5% over its label.1 A person dosing by those labels would take more than intended.
  • Retatrutide. Three products sold as retatrutide in Australia, each labelled with the same content, held 51%, 190% and 165% of it.2
  • Melanotan II. Vials bought from three online shops held between 43% and 88% of what each shop claimed.3

Dosing errors also happen with legitimate vials. A poison control centre reported three cases of semaglutide from compounding pharmacies and a spa, two of them tenfold dosing errors, partly because vials and syringes measure in millilitres and units rather than in the drug's own amount.9 FDA says it has received reports of adverse events, some requiring hospitalization, that may be related to dosing errors with compounded semaglutide; as of May 31, 2026 it had received 990 adverse event reports for compounded semaglutide and more than 730 for compounded tirzepatide.8 Grey-market products add the label inaccuracy above to that risk (our reasoning). For how a vial's contents become a dose, see our reconstitution calculator; for doses, see each compound's dosing box in the encyclopedia.

Contamination and impurities

Health Canada lists the contamination it is concerned about in unauthorized injectable peptides: solvents, heavy metals, particles such as fibres, glass or plastic, and microbes including bacteria, fungi and endotoxins.10 Australia's regulator says that with unapproved peptides the biggest risk is not knowing what is in the vial, including its quantity, sterility, contaminants and toxins.11

Published measurements of impurities are fewer than measurements of content. In the melanotan II study, vials from two of the three shops contained unidentified impurities of 4.1% to 5.9%; no pharmacopoeial standard exists for melanotan II, so there is no limit to judge them against.3 For compounded products, an analysis of FDA's adverse event reporting system from 2018 to 2024 found 707 reports involving compounded GLP-1 drugs, which had higher reporting odds than the approved products for contamination and for compounding or manufacturing issues.12 That analysis covers compounded products, not grey-market ones; we found no comparable analysis of grey-market products.

Endotoxin

Endotoxins are lipopolysaccharides from the outer membrane of gram-negative bacteria, released when the bacteria die. Fever is their best-known effect, and they "are not removed by sterilizing or microbiological filters", so a product can be sterile and still carry endotoxin.7 Approved injectables are tested for it before release; a grey-market buyer usually has only the seller's certificate, if any (see how to evaluate a peptide vendor).

One published test measured it in grey-market vials. In the semaglutide study above, endotoxin was measured at 8.9511 EU/mg in one vial, which the authors said indicated potential environmental contamination during production; the other two vials were reported only as below the assay's limit.1 The study stated no acceptance limit for these products, so the figure is reported here without a pass or fail.

Sterility

The same study tested the freeze-dried powder in all three vials for sterility under the European and US pharmacopoeias and found no viable microorganisms at the time of testing.1 That result covers the powder as it arrived. It does not cover the vial after water is added, a needle has pierced the stopper several times, or the solution has been stored (our reasoning; the study did not test reconstituted vials).1 Australia's regulator lists sterility among the unknowns of unapproved peptides.11

Heavy metals

Health Canada names heavy metals among the contaminants it is concerned about in unauthorized peptides.10 We found no published test that measured heavy metals in a grey-market peptide product (our own search of PubMed and the test reports behind our results page, October 28, 2026). That is an absence of evidence, not evidence of absence: no one has published the measurement, so the risk is unknown rather than shown to be low. Our article on why purity is not safety explains the limits approved injectables must meet.

Injection reactions and infection

Most grey-market peptides are injected under the skin. A 2026 review of growth-hormone-axis peptides sold as research compounds lists injection-site reactions among the adverse effects reported, alongside hormonal and metabolic effects, fluid retention and muscle and joint pain.14 In interviews with 30 people who inject image and performance enhancing drugs, participants described anxiety about injection-site reactions and limited knowledge of safe technique, with needle reuse and poor hygiene raising the risk of infection.13

Some reactions are unusual. Clinicians in Glasgow reported ulcers forming at the injection sites of a woman using melanotan, diagnosed as pyoderma gangrenosum, which needed months of steroid treatment to heal.15 Our page on contamination, rashes and injection reactions covers how an expected reaction differs from an infection or an allergy, what a contaminated vial looks like, and when to get care.

Harm from unsupervised use

A product can be exactly what its label says and still cause harm when it is taken without a clinician. Case reports published in 2026 describe:

  • an 18-year-old who developed euglycemic ketoacidosis ten days after starting semaglutide bought online, treated in hospital; the authors named possible high-dose initiation and uncertain dosing and purity of the product as contributing factors;17
  • a man with type 1 diabetes admitted with severe vomiting, ketonaemia and acute kidney injury after injecting a product sold online as retatrutide, with a Shigella infection at the same time, so the author could not separate the two causes;18
  • a 21-year-old who obtained tirzepatide through an online medical service and developed starvation ketosis, later diagnosed with anorexia nervosa.16

The third case involved a real prescription service, not the grey market, which shows the risk is about supervision as well as supply (our reading of the case). Each compound's own side effects are on its encyclopedia entry.

What testing can and cannot settle

Independent testing answers some of these questions for one vial: whether the molecule is there, how much, and sometimes endotoxin and sterility. It cannot speak for other vials in the batch, other batches, or what happens after the vial is opened (our reasoning). Gel and antibody methods confirm identity but do not measure purity or amount; that needs chromatography or mass spectrometry, which is why the follistatin and ACE-031 findings above are identity findings only.45 Our verification guide explains each test and what a certificate can and cannot show.

Frequently asked questions

Are grey-market peptides usually the right compound?

Smaller peptides tested in published studies were mostly the labelled molecule, but often in the wrong amount. Larger proteins fared worse: 8 of 17 products sold as follistatin 344 held none, and none of 14 sold as ACE-031 held it.45

Can a sterile vial still contain endotoxin?

Yes. Endotoxin comes from bacteria and is not removed by sterilizing filters, so sterility and endotoxin are separate tests.7

Have grey-market peptides been tested for heavy metals?

We found no published test that measured them, as of October 28, 2026. Health Canada lists heavy metals among the contaminants it is concerned about.10

Where can I see the lab results?

Every published test we have found is on our test results page, with the laboratory, method, date and source of each result, failures included.

Grey market hub Buyer's guide: start here Financial risks Legal risks How buyers find sellers, and the scams The 2025 China crackdown Contamination and skin reactions US warehouses and domestic stock What 'research use only' means Chinese peptides explained Peptide raves and group buys Peptides on Amazon, Temu and TikTok Shop How to evaluate a peptide vendor Purity is not safety Grey-market glossary

Sources

Product tests and case reports were read at PubMed; regulators' pages are quoted with the date they show. All read October 28, 2026. The test rows are collected, with methods and dates, on our published test results page.

  1. Ashraf AR, et al. Multifactor Quality and Safety Analysis of Semaglutide Products Sold by Online Sellers Without a Prescription: Market Surveillance, Content Analysis, and Product Purchase Evaluation Study. J Med Internet Res. 2024;26:e65440. PMID 39509151. Labelling accuracy, endotoxin and sterility from the full text (rows LR-0001 to LR-0012 on our results page). Source
  2. Piatkowski T, Craven A, Cornell S, Ferris J. Composition and Labelling Accuracy of Products Sold as Retatrutide in Australia. Drug Alcohol Rev. 2026;45(6):e70231. PMID 42559975 (rows LR-0013 to LR-0016). Source
  3. Breindahl T, et al. Identification and characterization by LC-UV-MS/MS of melanotan II skin-tanning products sold illegally on the Internet. Drug Test Anal. 2015;7(2):164-72. PMID 24771717 (rows LR-0017 to LR-0019). Source
  4. Reichel C, Gmeiner G, Thevis M. Detection of black market follistatin 344. Drug Test Anal. 2019;11(11-12):1675-97. PMID 31758732 (rows LR-0024 and LR-0025). Source
  5. Reichel C, Filip T, Gmeiner G, Thevis M. Gel Electrophoretic Detection of Black Market ACE-031. Drug Test Anal. 2025;17(10):1934-1946. PMID 40312924 (rows LR-0029 to LR-0031). Source
  6. Venhuis BJ, Keizers PHJ, Klausmann R, Hegger I. Operation resistance: A snapshot of falsified antibiotics and biopharmaceutical injectables in Europe. Drug Test Anal. 2016;8(3-4):398-401. PMID 26456392. Source
  7. U.S. Food and Drug Administration. Inspection Technical Guide: Bacterial Endotoxins/Pyrogens. Content current as of November 17, 2014; read October 28, 2026. Source
  8. U.S. Food and Drug Administration. FDA's concerns with unapproved GLP-1 drugs used for weight loss. Content current as of October 1, 2026; read October 28, 2026. Source
  9. Lambson JE, Flegal SC, Johnson AR. Administration errors of compounded semaglutide reported to a poison control center-Case series. J Am Pharm Assoc. 2023;63(5):1643-1645. PMID 37392810. Source
  10. Health Canada. Think twice before injecting peptides bought online: unauthorized products can seriously harm your health. Public advisory, April 9, 2026; read October 28, 2026. Source
  11. Therapeutic Goods Administration (Australia). TGA warning on the risks of importing unapproved peptide products. Safety alert, no date shown; read October 28, 2026. Source
  12. McCall KL, et al. Safety analysis of compounded GLP-1 receptor agonists: a pharmacovigilance study using the FDA adverse event reporting system. Expert Opin Drug Saf. 2026;25(3):581-588. PMID 40285721. Source
  13. Piatkowski T, et al. Making 'safer injecting' matter for people who inject image and performance enhancing drugs. Health (London). 2026;30(4):516-537. PMID 41204776. Source
  14. Dominikowski A, et al. The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration. Front Endocrinol. 2026;17:1822475. PMID 42395176. Source
  15. Dickson D, Hlaing Htwe S. Pyoderma Gangrenosum Secondary to Melanotan. Cureus. 2025;17(12):e98297. PMID 41487785. Source
  16. Yasui-Furukori N, et al. Starvation ketosis following self-administered tirzepatide obtained via online services in a young woman later diagnosed with anorexia nervosa: a case report. J Eat Disord. 2026;14(1). PMID 42243968. Source
  17. Sterckx M, De Keyser L. Euglycemic Ketoacidosis Following the Use of Counterfeit Semaglutide for Weight Loss. Cureus. 2026;18(1):e102627. PMID 41773123. Source
  18. Branine N. Online-Sourced Retatrutide Complicating Impending Diabetic Ketoacidosis in a Patient With Type 1 Diabetes and Concurrent Shigella Gastroenteritis. Cureus. 2026;18(8):e115260. PMID 42669023. Source
  19. Cox HD, Miller GD, Eichner D. Detection and in vitro metabolism of the confiscated peptides BPC 157 and MGF R23H. Drug Test Anal. 2017;9(10):1490-8. PMID 28035768 (row LR-0026). Source

This page describes how the grey market works; it is not legal or medical advice, and it is not a guide to buying. Grey Peptides sells nothing, links to no seller and rates none. If you have taken a product and feel unwell, contact a clinician or Poison Help (1-800-222-1222 in the US).