Testing and fakes
What independent tests of peptide products have found, what a test can and can’t tell you, and the claims to read carefully. No sellers or testing labs are named here.
What tests of real products found
Published analyses of products bought online or seized, and what regulators found in the paperwork sent to them.
| Product | Tested | What they found | Source |
|---|---|---|---|
| Semaglutide from illegal online pharmacies | 6 orders | 3 prefilled pens never arrived. The 3 vials that did held 29 to 39% more semaglutide than labeled, all carried bacterial toxins (endotoxin), and purity measured 8 to 14% against the 99% claimed. | Ashraf et al., J Med Internet Res 2024 |
| Products sold as SARMs | 44 products (2016) | Only 23 contained a SARM. 17 held other unapproved drugs, including MK-677, 4 held no active drug, 11 had ingredients not on the label, and the amount matched the label in 18. | Van Wagoner et al., JAMA 2017 |
| Melanotan 2 | Vials from 3 online shops | Labeled 10 mg, the vials held 4.3 to 8.8 mg; two shops’ vials had 4.1 to 5.9% unknown impurities. | Breindahl et al., Drug Test Anal 2015 |
| TB-500 and related products | 3 products | TB-500 products didn’t consistently match their own descriptions, and one product sold as a growth factor was mostly sheep tissue and blood proteins. | Delcourt et al., Drug Test Anal 2023 |
| Growth hormone and GHRP powders | Seized black-market products | A growth hormone with an extra amino acid, and glycine-extended versions of GHRP-2, GHRP-6 and ipamorelin: variants whose effects in people are unknown. | Krug et al., Growth Horm IGF Res 2018 |
| Custom research peptides | 2 peptides from a commercial supplier | 20% and 43% of each sample’s weight was mannitol, a sugar alcohol nobody declared. The usual purity test, HPLC with UV detection, can’t see it; NMR found it. | Choules et al., J Pharm Biomed Anal 2020 |
| Glutathione injections | An outbreak, 2026 | Injections compounded from supplement-grade powder caused reactions to bacterial toxins, including low blood pressure and shock, in more than 25 people in at least 4 states. | CDC, September 2026 |
| Certificates of analysis sent to FDA | Peptides nominated for compounding (2024–2026) | For peptides such as BPC-157, MOTS-c and CJC-1295 (no DAC), certificates lacked tests for impurities, microbes or endotoxins; some listed purity alone. | FDA advisory committee briefings |
What a test can and can’t show
| Test | Shows | Can’t show |
|---|---|---|
| Mass spectrometry | That the molecule has the right mass, so it’s probably the right peptide | How much is there, or whether it’s sterile |
| HPLC purity | What share of the peptide-like material, by UV signal, is the target peptide | Salt, water and fillers such as mannitol, so not how much peptide the vial holds |
| Assay (content) | How many milligrams of peptide the vial actually holds | Impurities or contamination |
| Endotoxin | Fragments of bacteria that cause fever and inflammation | Whether live microbes are present |
| Sterility | Whether live microbes grow from the sample | Endotoxin, which can be present in a sterile product |
Every result describes one sample from one lot, on the day it was tested. Reading a lab report explains each test in more detail.
Claims to read carefully
Usually an HPLC number. It describes the peptide-like material, not how much peptide is in the vial, and it can miss salt, water and fillers entirely, as the mannitol case shows.
Ask which lot was tested, by whom, for what, and when. A certificate that lacks a lot number matching your vial, or covers identity and purity only, leaves out most of what matters for an injection.
No regulator checks these products. In 2026, FDA rejected the disclaimer in warning letters where sellers’ websites showed the products were meant for people, and Australia’s TGA says it doesn’t make importing them lawful.
No approved semaglutide or tirzepatide product is a powder to mix: the approved forms are ready-made solutions and tablets, dispensed by licensed pharmacies on a prescription. FDA is aware of counterfeit Ozempic in the US market.
Sources: Ashraf et al., J Med Internet Res 2024, PMID 39509151; Van Wagoner et al., JAMA 2017, PMID 29183075; Breindahl et al., Drug Test Anal 2015, PMID 24771717; Delcourt et al., Drug Test Anal 2023, PMID 36482504; Krug et al., Growth Horm IGF Res 2018, PMID 29864719; Choules et al., J Pharm Biomed Anal 2020, PMID 31671336; CDC, adverse events linked to injectable glutathione (September 2026); FDA Pharmacy Compounding Advisory Committee briefing documents (2024–2026); FDA warning letters to online sellers (March 31, 2026); FDA, concerns with unapproved GLP-1 drugs used for weight loss; TGA, responsibilities when importing unapproved peptide products (checked October 2026).