Evidence review: Open Peptide Project (verified against primary PubMed, ClinicalTrials.gov & FDA records) · Last checked 2026-10-27. ← Back to Evidence Library

Counterfeit and mislabeled gray-market peptides

Name: Counterfeit and mislabeled gray-market peptides
Published: 2026-10-27

What independent testing and drug-safety databases show

Evidence verdict: Consistent observational evidence from test purchases, seizures and pharmacovigilance that unregulated products are often mislabeled, underdosed, overdosed or contaminated.

Last reviewed: Oct 27, 2026

In 30 seconds

In 44 products sold online as SARMs, only 52% contained a SARM and only 41% matched the labeled amount. [Observational]
Online semaglutide test purchases: all delivered vials judged probable substandard or falsified, low purity, endotoxin in every sample, and the ordered pens never arrived. [Observational]
Seized doping material has contained modified versions of GHRP-2, GHRP-6, ipamorelin and modified GRF 1-29 not matching any approved drug. [Lab, forensic]
EudraVigilance holds 234 case reports linked to possible counterfeit semaglutide (2018-2025); 89.3% of the suspected reactions were serious. [Observational]

Test-purchase studies

Semaglutide (PMID 39509151): 134 of 317 pharmacy links went to 59 illegal sites; delivered vials had measured purity of 7.7% to 14.37% versus a 99% label claim and endotoxin in all samples, and none of three ordered pens arrived. [Observational] SARMs, US (PMID 29183075): of 44 products, 23 contained a SARM, 17 contained another unapproved drug, 4 had no active compound, and 11 contained unlisted substances. [Observational] SARMs, Italy (PMID 38560649): about 70% contained the stated SARM; 30% contained undeclared drugs such as tamoxifen, clomifene, testosterone or tadalafil; content ranged from 30% to 90% of the label; sites claimed "for research only" while giving use instructions. [Observational]

Forensic and doping-lab findings

Danish customs seizures contained analogs of GHRP-2, GHRP-6, ipamorelin and modified GRF 1-29 with an extra N-terminal glycine (PMID 30136411). Black-market GH products included a 192-amino-acid variant and other analogs (PMID 29864719). [Lab, forensic] Researchers bought custom peptides and found 20% to 43% undeclared mannitol (PMID 31671336). [Lab]

Harms reported

Pharmacovigilance shows hypoglycemia and "drug ineffective" reported more often with possible counterfeit than genuine semaglutide (PMID 42137313). [Observational] A case report describes euglycemic ketoacidosis in an 18-year-old who self-administered semaglutide bought online (PMID 41773123). [Case]

What FDA says

FDA says counterfeit medicines may contain the wrong ingredients, too much, too little or no active ingredient, or other harmful ingredients (FDA counterfeit medicine page, updated 10/16/2026), and points consumers to state-licensed pharmacies for GLP-1 drugs (FDA GLP-1 page). [Regulatory] This page names no sellers or testing services.

Evidence levels used on this page

[Regulatory] FDA, USP or WADA primary document. [Controlled study] randomized trial or systematic review of trials. [Observational] market surveillance, pharmacovigilance or cohort data. [Lab] cell, analytical or animal work. [Case] single case report.

How to read a peptide COA, Research-use-only peptides and FDA law

References

Van Wagoner RM, et al. Chemical composition and labeling of substances marketed as selective androgen receptor modulators and sold via the internet. JAMA. 2017. PMID 29183075.
Ashraf AR, et al. Multifactor quality and safety analysis of semaglutide products sold by online sellers without a prescription. J Med Internet Res. 2024. PMID 39509151.
Gaudiano MC, et al. Illegal products containing selective androgen receptor modulators purchased online from Italy. Sex Med. 2024. PMID 38560649.
Gajda et al. Glycine-modified growth hormone secretagogues identified in seized doping material. Drug Test Anal. 2019. PMID 30136411.
Krug O, et al. Analysis of new growth promoting black market products. Growth Horm IGF Res. 2018. PMID 29864719.
Choules MP, et al. NMR reveals an undeclared constituent in custom synthetic peptides. J Pharm Biomed Anal. 2020. PMID 31671336.
Zinzi et al. Unmasking counterfeit semaglutide: real-world safety data from EudraVigilance. Front Pharmacol. 2026. PMID 42137313.
Sterckx et al. Euglycemic ketoacidosis following the use of counterfeit semaglutide for weight loss. Cureus. 2026. PMID 41773123.
US FDA. Counterfeit medicine. https://www.fda.gov/drugs/buying-using-medicine-safely/counterfeit-medicine
US FDA. FDA's concerns with unapproved GLP-1 drugs used for weight loss (content current as of 10/01/2026). https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss

Disclaimer: This page is for education only. It is not medical advice, and it does not endorse using, buying or preparing any unapproved product. Talk to a licensed clinician before you start, stop or change any treatment.