FDA issues a batch of peptide warning letters naming tirzepatide

The U.S. Food and Drug Administration issued warning letters dated August 24, 2026 to three companies that sell peptides online, citing tirzepatide, semaglutide, retatrutide and other GLP-1-type compounds as unapproved new drugs ^[1][2][3]. The letters went to NuScience Peptides LLC of Cornelius, North Carolina ^[1]; Royal Peptides LLC of Boynton Beach, Florida ^[2]; and TXP Innovations LLC, doing business as Tex Peptides, of Dallas, Texas ^[3].

All three letters came from the Center for Drug Evaluation and Research and were signed by Tina Smith, director of the Office of Unapproved Drugs and Labeling Compliance ^[1][2][3]. Each was based on an FDA review of the company's website in July 2026 ^[1][2][3].

What the letters say

The agency listed specific products at each site. At NuScience, FDA named "GLP-2 Tirz Peptide," "GLP-1 Sema Research Peptide," "GLP-3 RT (Retatrutide) Research Peptide," survodutide, mazdutide, PT-141, tesamorelin, a tesamorelin-ipamorelin blend, and bacteriostatic water ^[1]. At Royal Peptides, the list included tirzepatide, semaglutide, retatrutide, SS-31 (elamipretide), PT-141, tesamorelin and a blend called "BIMORELIN" ^[2]. At Tex Peptides, FDA named "Semaglutide (GLP-1 SEM)," "Tirzepatide (GLP-2 TRZ)," "Retatrutide (GLP-3 RT)," SS-31, tesamorelin, PT-141 and "Bacteriostatic Water 0.9% Benzyl Alcohol (10 ml)" ^[3].

FDA's core finding is the same in each letter: these are drugs under the Federal Food, Drug, and Cosmetic Act because the websites describe them as treating disease or affecting the body's functions, and no approved applications are in effect for them ^[1][2][3]. Selling them across state lines therefore violates the law, the agency said ^[1][2][3].

The letters also dismiss the "research use only" disclaimers these sites carry. FDA wrote that despite labeling saying products are "for laboratory, research, and analytical use" and "not intended for human or veterinary use," website evidence shows they are intended as drugs for human use ^[1]. The agency pointed to the sale of bacteriostatic water alongside a "peptide calculator" — resources that, in FDA's words, "provide the means to prepare an injectable drug for human administration" ^[1][2]. Because bacteriostatic water is sold to reconstitute injectable peptides, FDA classified the water itself as a drug ^[1][3].

Some of the marketing language FDA quoted is explicitly about weight loss. Royal Peptides' site said tirzepatide "has led to up to 22.5% body weight reduction in participants over 72 weeks—comparable to or even better than Semaglutide (Wegovy, Ozempic)," and that early retatrutide trials suggest "up to 24.2% body weight reduction in just 48 weeks" ^[2]. Tex Peptides described its tirzepatide product as "a promising therapeutic option in endocrinology and obesity research" ^[3].

Each letter includes the same public health warning: injectable products "bypass some of the body's key defenses against toxins and microorganisms that can lead to serious and life-threatening conditions" ^[1][2][3].

Why it matters for patients

Gray-market peptide sites have become a low-cost channel for people who want GLP-1 drugs without a prescription or insurance coverage. These letters are a reminder that what those sites sell is not the same product as FDA-approved Mounjaro or Zepbound (tirzepatide) or Ozempic, Wegovy or Rybelsus (semaglutide). Retatrutide, survodutide and mazdutide are investigational and have no FDA approval at all ^[1][2][3].

Because these products have no approved application, they are not made under the manufacturing and testing rules that apply to approved drugs, and FDA says they are not generally recognized as safe and effective ^[1][2][3]. The letters do not state what was actually in any vial — FDA's review was of website claims, not laboratory testing of the products. Nothing in the letters reports specific injuries tied to these three sellers.

The "research use only" label does not change FDA's view of what the products are, and it does not mean a product has been tested for sterility or potency. There is also no prescriber or pharmacist involved in these sales to check for drug interactions or contraindications.

What happens next

Each company has 15 business days from receipt to send a written response to FDA describing corrective steps, referencing its case number — 733652 for NuScience, 734884 for Royal Peptides, 735067 for Tex Peptides ^[1][2][3]. FDA warned that failure to address the violations may lead to action "without further notice including, without limitation, seizure and injunction" ^[1][2][3]. Whether the companies respond or change their sites is not yet known.