FDA to Peptide Sellers: "Research Use Only" Is Not a Defense. What the New Warning Letters Mean in Florida

If you sell peptides online and you have been relying on a research use only label to keep you clear of the Food, Drug, and Cosmetic Act, the FDA has now told you in writing that the label does not do that work. On September 1, 2026 the agency posted a batch of warning letters to online peptide sellers. The letters are dated August 24. One of the recipients operates out of Palm Beach County. Each letter says a version of the same thing: the disclaimer on the vial does not decide what the product is. Your website does.

FDA built the August 24 warning letters out of the sellers' own product pages. No inspection, no subpoena, no undercover buy.

Key Takeaways

• FDA now treats a seller's own website copy, not the vial label, as the evidence of intended use under 21 CFR 201.128.
• Shipping an unapproved new drug in interstate commerce violates 21 U.S.C. 331(d) and 355(a) even if no customer is ever harmed.
• Selling bacteriostatic water, dosing guides, and reconstitution calculators beside the vials is cited as proof of human injection intent.
• Criminal exposure runs through 21 U.S.C. 333, and prosecutors routinely add wire fraud under 18 U.S.C. 1343 when marketing is part of the conduct.
• South Florida is an active enforcement corridor, and a warning letter is frequently the paper trail a later federal case is built on.

What the Letters Actually Say

The agency reviewed the sellers' websites, not their warehouses. That is the first thing to notice. No inspection, no subpoena, no undercover buy. FDA compliance staff read the product pages in July and built the violations out of the sellers' own marketing copy.

The products cited across the letters include tirzepatide, semaglutide, retatrutide, tesamorelin, PT-141, SS-31, and blended growth-hormone secretagogue kits. FDA called each one an unapproved new drug under section 505(a) of the Act, 21 U.S.C. 355(a), and said that introducing them into interstate commerce violates 21 U.S.C. 331(d). A product becomes a drug under 21 U.S.C. 321(g)(1) when it is intended to treat disease or to affect the structure or function of the body. Intended use is defined by regulation at 21 CFR 201.128, and the regulation looks at the objective evidence of what the seller meant, not at what the seller wrote on a sticker.

The vial is not the evidence. The product page is. FDA read appetite suppression claims, percentage body-weight figures, and once-weekly dosing language, and treated all of it as a statement about what the seller intended the product to do.

The quoted evidence in the letters is ordinary product-page language. Claims about appetite suppression. Percentage body-weight reductions from published trials. Once-weekly dosing. Comparisons between two compounds on which one produces more weight loss. Descriptions of mitochondrial repair, anti-aging, and neuroprotection. None of that reads as laboratory supply copy, and FDA said so.

The footnote is the part sellers should sit with. FDA acknowledged the research use only and not for human or animal consumption statements, then set them aside, because the same sites sold bacteriostatic water next to a peptide guide and a dosing calculator. In the agency's words, those resources collectively provide the means to prepare an injectable drug for human administration. The disclaimer and the reconstitution kit cannot both be true.

What the Government Is Building

Warning letters are not charges. They are also not nothing. A warning letter establishes notice, and notice is what converts a regulatory problem into a criminal one. The misdemeanor offense under 21 U.S.C. 333(a)(1) does not require intent at all. The felony under 333(a)(2) requires that the violation be committed with intent to defraud or mislead, or that it follow a prior conviction. A letter in the file, unanswered or answered badly, is the government's cleanest proof that the seller knew.

The pattern across recent compounded drug enforcement is consistent. FDA opens on paper. The Office of Criminal Investigations gets involved when the conduct continues after notice, when the volume is significant, or when a patient is injured. Then the United States Attorney's Office adds the charges that actually drive a sentence, because the FDCA counts carry low statutory maximums and the fraud counts do not.

FDA opens on paper. The Office of Criminal Investigations arrives when the conduct continues after notice, when the volume is significant, or when someone is hurt. By then the record has already been written.

There is a second front. State boards and state pharmacy regulators are sharing findings with federal agencies, and med spa FDA investigation activity has been feeding the same pipeline. A clinic that bought from a cited seller is now discoverable. So is every invoice.

Exposure and Charges

Start with the FDCA counts. Introduction of an unapproved new drug and misbranding under 21 U.S.C. 331 carry, at the felony tier, up to three years under 21 U.S.C. 333(a)(2). Standing alone that is a manageable number. It is almost never standing alone.

The counts that move a guideline range are the fraud counts. If the seller took money over the internet on the strength of representations the government calls false, the wire fraud statute at 18 U.S.C. 1343 is available, with a twenty-year statutory maximum per count. Where two or more people ran the operation, 18 U.S.C. 371 conspiracy follows. Loss under the guidelines is then calculated on gross receipts, and a seller who moved seven figures through a payment processor is looking at a very different range than the three-year FDCA ceiling suggests.

Forfeiture travels with all of it. So does the inventory. A seller who assumes the worst case is a fine and a shutdown is working from the wrong ceiling. The government has already run this theory against peptide marketing claims as wire fraud.

The Mistakes That Turn a Letter Into a Case

Answering the letter without counsel. The response goes to the agency in writing and it is kept. Anything in it that is inaccurate, or that concedes knowledge the government would otherwise have to prove, becomes evidence. This is the single most common unforced error.

Editing the website and doing nothing else. Taking down the dosing calculator does not undo the archived pages, the customer emails, or the order records. It does create a timeline the government will describe as consciousness of guilt.

Talking to agents at the door. If FDA OCI investigators or federal agents come to a business or a home, the interview is not a chance to explain. It is the government collecting statements. Knowing what to do before charges are filed starts with declining the interview politely and calling a lawyer.

"Those resources collectively provide the means to prepare an injectable drug for human administration."— FDA warning letter to an online peptide seller, dated August 24, 2026

Waiting. A seller who is a subject of a federal investigation and treats a warning letter as the end of the matter usually learns otherwise when a federal grand jury subpoena arrives for the merchant-account records.

What Early Defense Work Actually Accomplishes

An FDA warning letter response is a legal document, not customer service. Done properly it does three things. It corrects the record where the agency's factual premises are wrong. It documents a genuine corrective plan, which is the strongest available argument against the intent to defraud or mislead element in a later felony theory. And it says nothing that a prosecutor can quote back.

Alongside that, the business needs a hold on documents, a clear-eyed look at the payment and shipping records, and an honest assessment of what a forensic review will show. Pre-indictment defense in this area is largely an exercise in shaping what the government finds and how it reads when they find it.

Where the facts are bad, the conversation with the Assistant United States Attorney is better had early than late. Charging decisions in FDCA and compounded drug matters are genuinely discretionary, and the difference between a civil resolution, a misdemeanor plea, and a fraud indictment is frequently decided months before anyone files anything.

Why the Timing Is Short

The letters give fifteen business days to respond. That deadline is real, and it is not the one that matters most. The real clock is the one running on the sellers who were not in this batch.

FDA reviewed these sites in July and posted the letters in September. The agency is working from public product pages, which means every peptide site on the open web is reviewable tomorrow at no investigative cost. The same is true of clinic sites that publish protocols and price lists. If a page on your site says what those pages said, the analysis has already been done. Only the letter is missing.

The window to fix a website, a supply chain, and a set of records while the matter is still regulatory is open right now. It closes on its own. Florida operators who want the longer view of how this enforcement wave started should read our earlier piece on the Florida peptide boom and federal criminal risk.

Common Questions

Facing an FDA Warning Letter or a Federal Investigation Involving Peptides?

AMC Defense Law represents sellers, compounders, clinics, prescribers, and owners in FDA and Department of Justice matters involving unapproved new drugs, compounded medications, and peptide distribution. The firm handles these matters at the pre-indictment stage, where the record is still being written, as well as after charges are filed. Consultations are confidential. If you have received a warning letter, a target letter, or a grand jury subpoena, or if agents have contacted you, call before you respond to anyone.

The warning letter response is a legal document that a prosecutor may read two years later. AMC Defense Law drafts it that way from the first draft.

If you or your loved ones have been arrested or contacted by federal agents over peptide sales, call Aaron M. Cohen for a confidential consultation, 24 hours a day to get help.

This article is provided for general informational purposes only and does not constitute legal advice. Reading it does not create an attorney-client relationship with AMC Defense Law or with Aaron M. Cohen. Every matter turns on its own facts, and federal enforcement policy changes. If you are the subject of a government inquiry, consult a licensed attorney about your specific situation. Prior results do not guarantee a similar outcome.

About the author: Aaron M. Cohen is the founder of AMC Defense Law, a federal criminal defense firm in Boca Raton, Florida. He is admitted to practice in Florida (Florida Bar No. 541427) and New York, and before the United States District Courts for the Southern District of Florida and the Southern District of New York. The firm represents clients in federal investigations and prosecutions involving healthcare fraud, Anti-Kickback Statute matters, DME and telemedicine fraud, peptide and compounded-drug enforcement, controlled-substance and drug conspiracy cases, financial crimes, and complex federal litigation, in Florida and nationwide.