FDA Warning Letters: 7 Peptide Shops Named for Retatrutide

Seven online shops have received letters from the US FDA because they have been selling weight-loss and diabetes injection powders as so-called "research chemicals" - substances that buyers mix and inject themselves.

Bottom line: On March 31, 2026 (published April 7, 2026), the US FDA sent seven warning letters to peptide research-chemical vendors for selling unapproved GLP-1 drugs (a family of gut-hormone-related medicines that includes popular weight-loss injections like Ozempic and Wegovy) and experimental triple-agonist drugs. The named companies are Gram Peptides, Mile High Compounds, Prime Sciences, Lovega, FormPour, Guangzhou Huli Technology, and PekCura Labs. The products are peptide hormones - mainly retatrutide, tirzepatide, cagrilintide, and mazdutide - that are either unapproved anywhere in the world or only available by prescription.

What do the warning letters actually say?

The FDA classifies every product on these websites as an unapproved new drug under Section 505(a) of the Federal Food, Drug, and Cosmetic Act. Specifically named in the letters:

• Retatrutide - marketed as "GLP-1-R peptide" or "GLP-3 RT"; an experimental triple agonist - imagine a single key that fits three different locks at once (GLP-1, GIP, and glucagon receptors) - not approved in any country.
• Tirzepatide - marketed as "GLP-2 peptide" or "GLP-2 TRZ"; pharmacologically tirzepatide is a dual agonist, meaning it activates two gut-hormone receptors (GIP and GLP-1) at the same time. The "GLP-2" label is merely misleading vendor terminology with no pharmacological basis. Tirzepatide is approved only as Mounjaro/Zepbound by prescription in the US, and only as Mounjaro by prescription in the EU.
• Cagrilintide and mazdutide - other peptide actives not approved in the US or EU.
• Bacteriostatic Water for Injection ("BAC Water" - sterile water containing a preservative that stops bacterial growth, used to dissolve peptide powders before injection) - also classified as a drug because it is sold alongside the peptides for reconstitution (mixing the powder with sterile water before injection).

The letters are dated March 31, 2026 and were published on the FDA website on April 7, 2026. Recipients must respond promptly or face seizure, injunction, and criminal enforcement.

Why does this matter for buyers in Europe?

Unlike earlier FDA waves that targeted telehealth platforms and compounding pharmacies (specialized US pharmacies allowed to mix custom drug preparations on a per-patient basis), this batch hits direct research-chemical shops - often no prescription, no medical supervision. Many European buyers source retatrutide or tirzepatide through exactly these channels because the substances cannot be prescribed legally outside approved indications.

Supply chains cross borders. A US warning does not by itself stop shipments to Europe, but it raises the risk of customs interception, sudden vendor shutdowns, and financial loss. In Australia, this gray market has already caused six documented liver injuries from counterfeit retatrutide; US lawsuits against clinics and vendors are also pending.

Which peptides are affected - and why are they risky?

Retatrutide is an experimental peptide hormone that targets GLP-1, GIP, and glucagon receptors simultaneously - again, three locks for a single key. Clinical trials have shown substantial weight loss (see Retatrutide Phase 3: Up to ~24 % Weight Loss), but it is not approved anywhere. Tirzepatide (see the tirzepatide page) is approved in the EU, but only as the prescription medicine Mounjaro. Selling it as a "research peptide" or "chemical" is illegal in both cases.

Independent lab tests from 2025 and 2026 show that a substantial share of research-grade peptides is contaminated with heavy metals, endotoxins (toxic fragments from bacteria that can trigger fever or shock), or the wrong active compound. An FDA warning adds another reason why sourcing from these shops is neither safe nor legal.

What should you do now?

• Stop all new orders with the named vendors immediately.
• Document any open orders - keep receipts, batch numbers, and chat logs.
• If you have already used a product: see a doctor and get bloodwork (liver, kidneys, blood count).
• If you suspect side effects: call poison control or your physician, and bring the vial.
• "Research Use Only" is not a free pass - the label does not protect you from criminal liability.

The named vendors are publicly tracked on Peptigraph's warning list as soon as a verification is on file.

No medical advice. This article is for informational purposes only about regulatory action and does not replace consultation with a qualified physician.