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Athletes · Contamination

Contaminated supplements and mislabelled peptides: the athlete's risk

An athlete is tested for what is in the body, not for what the label said. Analyses of supplements and of peptide products bought on the black market keep finding substances that were never declared, some of them prohibited. This page sets out what those analyses found.

Last updated November 3, 2026 · Reviewed by Grey Peptides Editorial Board · ✓ Every claim sourced · No products sold, no seller named

📋 Key takeaways

More than a quarter of supplements analysed in 50 studies held undeclared substances: 875 of 3,132.2

Even ordinary tablets: vitamin C, multivitamin and magnesium tablets have been found cross-contaminated with anabolic steroids.1

Peptide vials are no safer. Of 17 black-market follistatin products tested, only 9 contained follistatin, and some of the others held growth-promoting peptides such as MGF or GHRP-2.3

On this page

  1. What analyses of supplements found
  2. What tests of peptide products found
  3. What an athlete can do
  4. Frequently asked questions
  5. Related on Grey Peptides
  6. Sources

What analyses of supplements found

  • An international study, 2001 to 2002. Of 634 supplements bought in 13 countries, about 15% of the non-hormonal products were contaminated with anabolic-androgenic steroids, mainly prohormones, none declared on the label. Since then, products deliberately spiked with classic anabolic steroids, designer steroids and the stimulant clenbuterol have been found, and in 2005 confiscated vitamin C, multivitamin and magnesium tablets held stanozolol and metandienone. The authors warn of a high risk of inadvertent doping cases and a health risk.1
  • A 2022 review of 50 studies. Of 3,132 supplements analysed, 875 contained undeclared substances, most often sibutramine and anabolic steroids; the authors concluded that more than 28% posed a potential risk of unintentional doping.2

What tests of peptide products found

Peptides sold online as research chemicals carry the same risk, and the evidence is direct:

  • Follistatin. In a doping-control study of 17 black-market products, mostly labelled follistatin 344, only 9 actually contained follistatin; in some of the others, growth-promoting peptides such as MGF and GHRP-2 were found.3 An athlete who bought "follistatin" could have injected GHRP-2 or a mechano growth factor instead, each a different entry on the List (our reasoning; their status is on the WADA status page).
  • Seized products. Norway's doping control laboratory found peptide- and protein-based doping substances in 28% of black-market products seized in 2011 to 2014.4
  • Semaglutide. In a study of semaglutide bought online without a prescription, the products contained 28.6% to 38.7% more than their labels stated.5 See the semaglutide entry.

Our grey-market guide collects the published test results for other peptides, and our testing page covers how laboratories find what is in a sample.

What an athlete can do

  • Treat every product as a possible source of a positive test. The studies above found undeclared substances in ordinary-looking products and in vials labelled as something else.123
  • Prefer a regulated medicine to a research product. An approved medicine is made and labelled under a regulator's oversight; a research chemical is not, and the follistatin and semaglutide results show what that can mean (our reasoning, from sources 3 and 5).
  • Check the List, not the label. A label's claims say nothing about anti-doping status; the WADA status page and the WADA hub do.
  • Keep records. Batch numbers, receipts and a sealed sample of anything you take can matter if a result has to be explained (our reasoning).

Frequently asked questions

Can a supplement cause a positive doping test?

Yes. A 2022 review of 50 studies found undeclared substances, most often sibutramine and anabolic steroids, in 875 of 3,132 supplements analysed.

Is a peptide vial what its label says?

Not reliably. In one study only 9 of 17 black-market follistatin products contained follistatin, and some held other growth-promoting peptides.

Athletes, peptides and testing hub WADA status by compound The 2027 Prohibited List How testing finds peptides Therapeutic use exemptions WADA Prohibited List hub Do peptides show up on drug tests? Our report on the 2027 List TB-500 is not thymosin beta-4 The grey market

Sources

Studies are cited by PMID and checked on PubMed; figures are quoted from their abstracts. Read November 3, 2026.

  1. Geyer H, Parr MK, Koehler K, Mareck U, Schänzer W, Thevis M. Nutritional supplements cross-contaminated and faked with doping substances. J Mass Spectrom 2008;43(7):892-902. PMID 18563865. Source
  2. Kozhuharov VR, Ivanov K, Ivanova S. Dietary Supplements as Source of Unintentional Doping. Biomed Res Int 2022;2022:8387271. PMID 35496041. Source
  3. Reichel C, Gmeiner G, Thevis M. Detection of black market follistatin 344. Drug Test Anal 2019;11(11-12):1675-1697. PMID 31758732. Source
  4. Hullstein IR, Malerod-Fjeld H, Dehnes Y, Hemmersbach P. Black market products confiscated in Norway 2011-2014 compared to analytical findings in urine samples. Drug Test Anal 2015;7(11-12):1025-1029. PMID 26607218. Source
  5. 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. Source

This section reports the WADA Prohibited List, the anti-doping standards and published research, and our reading of them. It is not legal advice or an anti-doping ruling: an athlete's own anti-doping organisation gives the answer that counts. Grey Peptides sells nothing, links to no seller and rates none.