What FDA's 2026 peptide warning letters cite, sentence by sentence
FDA issued twelve warning letters to online peptide sellers in 2026: seven dated 31 March and posted 7 April, five dated 24 August and posted 1 September. Read side by side, they are one letter written twelve times. Each recites the seller's research-use-only disclaimer and sets it aside in a single sentence. Each reaches the drug definition through the seller's own website. Three of the March letters and all five of the August letters name bacteriostatic water as an unapproved drug in its own right. Two cite a peptide calculator or guide as evidence of what the products are for. And every product list places the storefront's coded name next to the compound it stands for. This piece quotes the agency's sentences, not the sellers', and the interactive readers below let you check each one against the letter it came from.
FDA warning letters to research-framed peptide sellers, by batch
Circle size is the number of letters dated that day. Select a batch to see who received one.
August 2026: 5 letters dated August 24, 2026
Posted September 1
Five letters. Every one names bacteriostatic water; two cite a peptide calculator or guide as evidence.
- TXP Innovations LLC dba Tex PeptidesMARCS-CMS 735067
- Royal Peptides LLCMARCS-CMS 734884
- NuScience Peptides LLCMARCS-CMS 733652
- Peptide Partners LLCMARCS-CMS 735063
- Peak Performance PeptidesMARCS-CMS 735127
Which sentence disposes of the disclaimer?
The same one, every time, varying only in the disclaimer it quotes back. To Gram Peptides on 31 March: "Despite statements on your product labeling marketing your products for 'Research Use Only,' and 'not intended for human consumption, medical use, or veterinary use,' evidence obtained from your website establishes that your products are intended to be drugs for human use." To Prime Sciences the same day, the disclaimer was "laboratory research purposes only." To NuScience Peptides on 24 August it was "for laboratory, research, and analytical use." The sentence around those quotations does not change.
What the construction does is worth stating exactly. FDA does not argue that the disclaimer is false, and it does not argue that the phrase is meaningless. It acknowledges the disclaimer and then says the website establishes a different intent. That is the intended-use rule at 21 CFR 201.128 applied as written: intent is objective, it is shown by labeling claims and advertising matter, and one statement does not settle it against the rest of the record. A disclaimer that sits above copy pointing the other way is outweighed, not overruled.
How do the letters define a drug?
Through both prongs of section 201(g)(1). The Gram Peptides letter puts it in one sentence: "Your products are drugs as defined by section 201(g)(1) of the FD&C Act because they are intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease and/or intended to affect the structure or function of the body." The "and/or" matters. The second prong, structure or function, does not need a disease to be named. Copy describing what a compound does in a body qualifies on its own.
The Prime Sciences letter then shows where the evidence came from. It introduces the quoted copy with: "Examples from your product labeling, including on your website, that provide evidence of the intended use (as defined in 21 CFR 201.128) of these products as drugs include". Two things sit inside that sentence. The website is called labeling. And the regulation cited is the objective-intent rule, so the copy is being read for what it objectively conveys, not for what the seller says it meant.
The copy FDA quoted is not reproduced here. It is in the letters, which are public, and restating it would be restating the language the agency treats as evidence.
Why is bacteriostatic water in the letters at all?
Because FDA treats it as evidence of what the peptides are for, and then as a drug itself. The Gram Peptides letter: "Your firm offers 'Bacteriostatic Water for Injection' for sale alongside peptide products, which are drugs intended for injection and require reconstitution, including the two above-mentioned GLP products." Then, two sentences later: "Therefore, your 'Bacteriostatic Water for Injection' is a drug." NuScience, five months on: "Your firm offers 'Bacteriostatic water for Peptides (BAC Water)' for sale to be used to reconstitute the peptide products sold on your website, which are drugs intended for injection".
The logic is combinational. A solvent for injection sold next to a compound tells the agency the compound is for injection. Once that is established, the solvent is offered "in combination" with a drug and is charged as one. In the August batch this appears in all five letters. It is the clearest example of a principle that runs through the whole series: the composition of a storefront is evidence, independent of any sentence written about a compound.
What about calculators and kits?
They are cited as evidence on their own terms. The Prime Sciences letter: "The sale of a kit containing the 'BAC water' and a means of injection (a syringe) with these peptide drugs demonstrates that you intend for the 'BAC water' to be used in combination for injection." The NuScience letter goes further and reaches tooling with no physical product attached: "you market bacteriostatic water alongside a 'peptide calculator,' a resource that provides the means to prepare an injectable drug for human administration".
That second sentence is the one with consequences for anyone publishing content about research peptides. A dosing or reconstitution calculator makes no claim about any compound. FDA cited it anyway, because a tool for preparing an injection is a statement about what the material is for. The same reasoning reaches dosing tables, reconstitution instructions and syringe-unit conversions wherever they appear on a site.
What the letters say, in FDA's words
Three letters read in full. Pick the kind of evidence, then narrow to one letter.
“Despite statements on your product labeling marketing your products for 'Research Use Only,' and 'not intended for human consumption, medical use, or veterinary use,' evidence obtained from your website establishes that your products are intended to be drugs for human use.”
The disclaimer is acknowledged, then set aside. It is not disputed; it is outweighed.
“Despite statements on your product labeling marketing your products for 'laboratory research purposes only' and 'not for human consumption, medical use or veterinary use,' evidence obtained from your website establishes that your products are intended to be drugs for human use.”
Same sentence, different disclaimer wording. The wording of the disclaimer made no difference.
“Despite statements on your product labeling marketing your products 'for laboratory, research, and analytical use' and 'not intended for human or veterinary use,' evidence obtained from your website establishes that your products are intended to be drugs for human use.”
Five months later, the construction is unchanged.
Did renaming the products help?
No. Every letter lists the products FDA is calling unapproved new drugs, and the lists pair the storefront's label with the compound. Gram Peptides: "Retatrutide (also referred to as "GLP-1-R peptide"), Tirzepatide (also referred to as "GLP-2 peptide"), Bacteriostatic Water for Injection". Prime Sciences: "Cagrilintide, GLP1-R, GLP1-S, GLP1-T, Mazdutide, and BAC water". NuScience: "GLP-2 Tirz Peptide, GLP-1 Sema Research Peptide, GLP-3 RT (Retatrutide) Research Peptide, Survodutide, Mazdutide, PT-141 Peptide (Bremelanotide), Tesamorelin Research Peptide, Tesamorelin Ipamorelin Blend, Bacteriostatic water for Peptides (BAC Water)".
Across the three letters read in full, retatrutide, tirzepatide and bacteriostatic water appear in all three. Coded names were listed as written and treated as the drug they denote. The word "Research" inside a product name was listed along with the rest.
What does a letter demand, and what does it not decide?
Each letter gives the same clock. March: "Please notify FDA in writing, within fifteen working days of receipt of this letter, of the specific steps you have taken to correct any violations." August: "Send your written response to FDAAdvisory@fda.hhs.gov within fifteen (15) business days of receipt of this letter."
A warning letter is the agency's position, not a court's. None of the twelve has been adjudicated, and none alleges a product-quality failure: no contamination, subpotency or misidentification is asserted in the letters read for this piece. The theory is intended use as shown by marketing, and the record used to prove it is the seller's own site.
What the twelve letters establish, together
Five things, each stated in FDA's own sentences above. A research-use-only disclaimer is acknowledged and outweighed, whatever its wording. Website copy is labeling, and the structure-or-function prong means it need not mention a disease. Bacteriostatic water sold alongside compounds is both evidence and, itself, an unapproved drug. Calculators, guides and kits are evidence without any claim attached to them. And a renamed product is listed beside its real name.
Veridian Research supplies material for in-vitro laboratory research only. This piece is a reading of public regulatory documents, not legal advice, and the citations are given so each sentence can be checked against its source.
Sources
FDA warning letters, all in the agency's public database by reference number: Gram Peptides, MARCS-CMS 721806, 31 March 2026. Prime Sciences, MARCS-CMS 721805, 31 March 2026. NuScience Peptides LLC, MARCS-CMS 733652, 24 August 2026. The remaining March recipients were Lovega LLC dba Pink Pony Peptides (721088), Mile High Compounds LLC (721600), PekCura Labs (721709), FormPour (722215) and Guangzhou Huli Technology dba Fantasy Face (722228). The remaining August recipients were TXP Innovations LLC dba Tex Peptides (735067), Royal Peptides LLC (734884), Peptide Partners LLC (735063) and Peak Performance Peptides (735127). 21 CFR 201.128 and 21 U.S.C. 321(g)(1) are quoted from the current text.