FDA sends warning letters to five peptide sellers listing retatrutide and semaglutide
The letters target injectable peptides sold online without FDA approval, a market that includes black market retatrutide linked to hospitalizations in the UK.
The Food and Drug Administration sent warning letters dated August 24, 2026 to five online sellers of peptide products whose websites listed retatrutide, semaglutide, tirzepatide, elamipretide and tesamorelin, along with bacteriostatic water, the liquid used to reconstitute powdered drugs. All five were cited for selling unapproved drugs [1].
Some of the companies sold their products as research-use drugs, and all of them were cited for selling unapproved drugs [1]. The names of the five companies have not been reported, and no recalls or product seizures tied to this batch of letters have been announced [1].
The letters add to a run of enforcement actions aimed at the gray market for injectable peptides and compounded GLP-1 drugs. The nonprofit Partnership for Safe Medicines says it has tracked 50 state pharmacy board actions against unsafe compounders and 160 FDA warning letters to telehealth companies and compounders, including 55 warning letters to GLP-1 compounders in the first half of 2026 [1]. The NBC Bay Area Investigative Unit has examined concerns over unapproved and compounded GLP-1 drugs, including reports of patients becoming seriously ill or hospitalized after taking them [1].
Retatrutide, an experimental weight loss drug from Eli Lilly that is not approved for sale, was among the drugs listed by the sellers. Because the drug has no established supply chain, any version taken outside a Lilly program is considered a black market drug [1]. Eli Lilly has called on online platforms, payment companies and regulators to act against compounding pharmacy sales of the drug, which the company says are illegal [1]. In the UK, doctors have warned about severe side effects as illicit supply has grown there; one doctor said young, fit patients are arriving at hospitals, some with kidney failure, and a 20-year-old who ordered what was sold as retatrutide from a Chinese supplier and accidentally took eight times the recommended dose described "horrendous" nausea and diarrhea [1].
Separately, the blockchain analytics firms TRM Labs and Chainalysis have reported that China-based chemical companies that produced fentanyl precursors have moved into the peptide business, continuing to sell fentanyl precursors while adding peptides [1]. A UCLA Health review of 565 studies covering six popular unapproved peptides — BPC-157, TB-500, CJC-1295, MK-677, ipamorelin and GHK-Cu — found little evidence that they provide meaningful benefits. More than two-thirds of the studies were conducted only in animals, and the limited human research was generally low quality, according to the researchers [1]. The review flagged an MK-677 trial that was stopped because of the risk of congestive heart failure and warned that unapproved products are unregulated and may contain undisclosed or dangerous substances [1].
Why it matters for patients
Peptides bought from these websites have not been through FDA approval for safety, effectiveness or manufacturing quality, which means there is no reviewed evidence on how they were made, what is in them or what dose a person is actually getting [1]. For the products sold as research chemicals, no quality oversight applies at all [1].
The letters also named semaglutide and tirzepatide, the molecules in approved prescription products, alongside retatrutide, elamipretide and tesamorelin [1]. The enforcement action is aimed at unapproved versions sold online, not at products dispensed through normal pharmacy channels.
Recent warnings from UK doctors about retatrutide users hospitalized with conditions including kidney failure illustrate what can happen when an unapproved injectable reaches people without a supply chain or medical oversight [1]. The UCLA researchers concluded that marketing claims about peptides are far ahead of the science [1].
What happens next
The FDA has not disclosed whether these letters will be followed by seizures, injunctions or recalls, and no timeline has been announced [1]. John Hertig, chair of the board of the Collaborative for Evidence-Based Medicines, has argued that state boards of pharmacy should investigate and take legal action against illegal sellers and issue public warnings, working with boards of medicine and nursing, state attorneys general and law enforcement [1]. Whether the FDA will publish the full letters or identify the companies has not been reported [1].
Sources
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