FDA's warning letters are the one public, dated, primary record of how the agency reads the research-peptide market. They name the seller, the website, the products and the sentences on the product pages that FDA treated as drug claims, and they say in FDA's own words why "research use only" did not help. This page collects every such letter we could find, keeps FDA's wording where it matters, and separates the letters about marketing from the two about what was in the product. It is a documentary page: nothing here is a test result of ours, and a vendor's absence from the table means only that we found no letter.
Rankings on Peptifact follow the published criteria and are never sold; how brands appear on this site is set out on our disclosure page. Warning-letter status is one input to the compliance section of our vendor protocol, described on the methodology page.
The letters, by date
All letters are from FDA's Center for Drug Evaluation and Research (CDER). "What FDA cited" gives the statutory sections in the letter; 301(d) and 505(a) of the Federal Food, Drug, and Cosmetic Act together mean "introducing an unapproved new drug into interstate commerce". Each row links to the letter on fda.gov.
| Letter date | Seller (as addressed) | Location | Products named | What FDA cited | Evidence FDA quoted |
|---|---|---|---|---|---|
| 2024-12-10 | Summit Research Peptides | Hoover, AL | Semaglutide, retatrutide, cagrilintide, tirzepatide, mazdutide | 301(d), 505(a) | Website and Facebook page; claims about diabetes treatment and weight loss |
| 2024-12-10 | Prime Vitality Inc. dba Prime Peptides | Santa Barbara, CA | Semaglutide, retatrutide, tirzepatide | 301(d), 505(a), 201(g)(1) | "Semaglutide reduces cardiovascular events"; "Retatrutide improves glycemic control"; Facebook, Instagram and YouTube reviewed |
| 2025-02-26 | USApeptide.com | Germany | Semaglutide 5 mg and 10 mg, tirzepatide 5 mg and 10 mg, bacteriostatic water 20 mL, insulin syringes | 301(d), 505(a); misbranding under 301(a), 301(k), 502(f)(1), 503(b)(1) | "Semaglutide ... is an FDA-approved injectable for weight loss"; syringes sold alongside |
| 2025-12-12 | Pinnacle Professional Research dba Pinnacle Peptides | Greensboro, NC | S4 (andarine), LGD-4033, MK-2866 (SARMs, not peptides) | 301(d), 505(a) | Therapeutic claims despite "FOR RESEARCH ONLY" and "NOT FOR HUMAN USE" labels |
| 2026-01-20 | GenoGenix LLC | Boca Raton, FL | Semaglutide, tirzepatide, retatrutide, thymosin beta-4, epithalon, NAD+, 5-amino-1MQ and others (a compounder) | 501(a)(2)(A) and (B) adulteration; 505(a), 301(d); 502(f)(1); 501(c) | Insanitary conditions; products at 43.1% to 65.3% of labeled strength |
| 2026-03-31 | Gram Peptides | Rancho Santa Fe, CA | Retatrutide ("GLP-1-R"), tirzepatide ("GLP-2"), bacteriostatic water | 301(d), 505(a) | "influences appetite suppression, insulin sensitivity, thermogenesis" |
| 2026-03-31 | Lovega LLC dba Pink Pony Peptides | Wellington, FL | "GLP-2 TZ", "GLP-3 RT", bacteriostatic water | 301(d), 505(a) | "Reduce appetite and increase satiety"; "fat-fighting horsepower" |
| 2026-03-31 | Prime Sciences | Scottsdale, AZ | Cagrilintide, retatrutide, semaglutide, tirzepatide, mazdutide, bacteriostatic water | 301(d), 505(a), 201(g)(1) | Trial results quoted on product pages: "Up to 28% body weight reduction" |
| 2026-03-31 | Mile High Compounds LLC | Clifton, CO | Semaglutide, tirzepatide, retatrutide, bacteriostatic water | 301(d), 505(a), 201(g)(1) | Weekly dosing schedules on the site and a Skool community |
| 2026-05-01 | Harbin Jixianglong Biotech Co., Ltd. | Harbin, China | Semaglutide and tirzepatide active pharmaceutical ingredient (an API manufacturer, not a retailer) | 501(a)(2)(B) adulteration; 510(j), 301(p) unlisted; 502(o), 502(a), 502(b)(1) misbranding | Shipped quantities exceeded R&D volumes; a proposed "Only for R&D use" certificate was rejected |
| 2026-06-17 | Wholesale Peptide | Brooksville, FL | Prostamax 20 mg, gonadorelin 5 mg | 301(d), 505(a) | "reduces chronic inflammation in the prostate"; "supports testes function" |
| 2026-08-24 | NuScience Peptides LLC | Cornelius, NC | Tirzepatide, semaglutide, retatrutide, survodutide, mazdutide, PT-141, tesamorelin, a tesamorelin-ipamorelin blend, bacteriostatic water | 301(d), 505(a) | A "peptide calculator" for preparing injectable doses; efficacy claims for survodutide and mazdutide |
| 2026-08-24 | Peak Performance Peptides | Phoenix, AZ | Bacteriostatic water, retatrutide, semaglutide, SS-31, PT-141, tesamorelin | 301(d), 505(a) | "studied for its potential effects on glucose regulation, appetite control" |
| 2026-08-24 | Royal Peptides LLC | Boynton Beach, FL | Tirzepatide, semaglutide, retatrutide, SS-31, PT-141, tesamorelin, "bimorelin" | 301(d), 505(a) | "up to 22.5% body weight reduction"; bacteriostatic water offered with peptide guides and calculators |
| 2026-08-24 | TXP Innovations LLC dba Tex Peptides | Dallas, TX | Semaglutide, tirzepatide, retatrutide, SS-31, tesamorelin, PT-141, bacteriostatic water 10 mL | 301(d), 505(a) | "helps regulate blood glucose levels"; "increase arousal and desire" |
| 2026-08-24 | Peptide Partners LLC | Sarasota, FL | Semaglutide, tirzepatide, retatrutide, SS-31, tesamorelin, PT-141, "Reconstitution Solution (BAC)" | 301(d), 505(a) | Bacteriostatic water marketed as a reconstitution solvent; claims about Alzheimer's, kidneys and breast cancer |
Two letters that surfaced in the same searches are not in the table because they are not about peptides: PureRawz (2025-09-08, tianeptine products, sold "for laboratory and research use only") and a June 2026 set of letters to telehealth companies over compounded semaglutide and tirzepatide (NativeMed, HydraMed IV, Nexus Health Solutions, FitRX, Altru Telehealth, Eden Health International, Trinity HealthCare Supply, all dated 2026-06-08). The first shows the same research-use-only argument being rejected outside peptides; the second is a different market, compounding pharmacies and their marketers, which this page does not cover — the permissions those operators work under, and the two separate ingredient lists attached to them, are set out in 503A vs 503B.
Two further letters fall outside the table by date rather than by subject, and a reader searching it for a nootropic compound will not find them here: FDA's letter of 2021-11-10 to a physician's compounding operation, which states that cerebrolysin, selank and semax, among others, "were not nominated for inclusion on the 503A bulks list", and its letter of 2022-02-04 to Crystal Clear Supplements, which cites "Noopept Powder" among unapproved new drugs and quotes the seller's own product copy as the evidence. Both are read in full on our cognitive peptides page, which takes those compounds through the primary record.
What FDA said about "research use only"
The disclaimer appears on every seller's labels. FDA's answer, in every letter that addressed it, is the same sentence with the seller's own wording substituted in. To Peak Performance Peptides: "Despite statements on your product labeling marketing your products for 'research use only' and 'not for human consumption,' evidence obtained from your website establishes that your products are intended to be drugs for human use." To Prime Peptides in 2024, the same construction with "research purposes only" and "not for human consumption or clinical use". To Summit Research Peptides, with "RESEARCH USE ONLY" and "INTENDED AS A RESEARCH CHEMICAL ONLY".
The evidence FDA then lists is never the vial. It is the copy around the vial. Across the letters, four kinds recur:
- Therapeutic claims on the product page, including trial results reported as if about the product: "Weight loss of 25% or more was achieved in 40.4% of patients" (Prime Sciences), "up to 22.5% body weight reduction" (Royal Peptides), "Semaglutide reduces cardiovascular events" (Prime Peptides).
- Bacteriostatic water sold beside the peptides, which FDA reads as a reconstitution solvent for injection. It appears in nine letters, and Peptide Partners' letter says so directly.
- Calculators, guides and dosing schedules. NuScience's "peptide calculator" for preparing injectable doses; Royal Peptides' guides and calculators; Mile High Compounds' weekly titration schedules.
- Social media and communities: Facebook, Instagram and YouTube for Prime Peptides, a Skool community for Mile High Compounds.
The lesson is not subtle. The disclaimer is a label; intended use is inferred from everything else the seller publishes, and FDA reads all of it.
There is a second half to this that the letters do not spell out, because they had no need to: the phrase is not a disclaimer a seller invented. It is the label text required by 21 CFR 312.160, a regulation that authorises shipping an investigational drug for laboratory use — and the label is one of four conditions, alongside due diligence about who the consignee is, records naming the recipient kept two years for FDA inspection, and the return of unused supplies. Our page on whether peptides are legal quotes the regulation in full.
Patterns worth knowing
- The GLP-1 wave. Semaglutide, tirzepatide or retatrutide appear in 12 of the 15 seller letters. The 2024 letters were the first to name retatrutide, a compound then in Phase 2; by August 2026 it was in five letters on one day. Whatever else these letters are, they are a map of where FDA's attention has been: on the compounds with a famous brand name attached.
- Enforcement comes in batches. Two letters on 2024-12-10, four on 2026-03-31, five on 2026-08-24. A seller reading about a competitor's letter on a given date has a reasonable expectation that others were sent the same day.
- Location tells you little. Florida (five sellers), then Arizona, California, Colorado, North Carolina, Texas and Alabama, plus Germany. The Germany letter, to USApeptide.com, shows that a foreign address does not put a US-facing site out of reach.
- Two letters are about what was in the product; thirteen are not. GenoGenix's products tested at 43.1% to 65.3% of labeled strength under insanitary conditions; Harbin's API was adulterated and unlisted. Every other letter is about marketing. A reader who conflates the two will conclude, wrongly, that a warning letter is a purity finding, or, equally wrongly, that a clean marketing record says anything about purity. What Harbin's letter found, set against FDA's GLP-1 import alert, is on our Chinese peptides page.
- No close-outs found. FDA posts a close-out letter when it is satisfied that violations were corrected. None of the letter pages we opened on 2026-09-05 showed one, and none showed a company response. Re-checked 2026-09-07: all sixteen letter pages linked in the table were fetched again and all sixteen still resolve, still carry the original letter text, and still show no close-out letter and no posted company response. The oldest two, to Summit Research Peptides and Prime Peptides, are dated 2024-12-10 and have now stood without a posted close-out for more than twenty months. We re-check monthly and note any change here with the date.
What a warning letter is, and is not
A warning letter is FDA's formal notice that it believes a company has violated the law, with a 15-working-day window to respond. It is not a court finding, an injunction or a product recall, and the company may contest it. It also says nothing about vendors who did not receive one. Several of the features FDA cited as evidence of intended human use are widespread in the market, including at vendors ranked on this site: Medibact sells bacteriostatic water and publishes a reconstitution calculator. Absence from this table is not a finding of compliance, and our vendor protocol treats it as exactly that, an absence.
How to check for yourself
- FDA's warning-letter database, searched by term:
https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/compliance-actions-and-activities/warning-letters?search_api_fulltext=peptides. Replace the last word with a company name or a compound. The results list the company, the letter date, the posting date and the issuing office; open the letter itself for the products, the website and the review date. - Read the first three paragraphs of the letter. They name the website and the date FDA reviewed it, the products, and the labeling statements FDA quotes. The evidence section that follows is the part sellers most often misdescribe.
- Check the posting lag. The August 2026 letters were dated 2026-08-24; they appeared in the database within the following two weeks. A search on the day of a rumored letter may find nothing.
- Do not treat this page as the database. It is what the searches described above returned on one date. The database is the record.
- A certificate of analysis is a separate question. Sellers named here often publish one, and it is a chemistry document with no bearing on regulatory status in either direction. What it does and does not certify is set out in how to read a certificate of analysis.
There is no machine-readable version of this record, and that is why it is tracked so badly
Anyone trying to monitor these letters automatically runs into a gap in FDA's own publishing, which we checked directly on 2026-09-07 and which a reader can reproduce in two requests.
openFDA, the agency's public API, carries no warning-letter dataset at all. Its endpoint index at https://api.fda.gov/download.json lists nine categories; the drug category offers Drugs@FDA, the Orange Book, labeling, enforcement (recalls), adverse events, shortages and the NDC directory. Warning letters are in none of them, for drugs or for any other category.
The one bulk file FDA does publish stops in 2021. The static datatable behind the warning-letter search, https://www.fda.gov/files/api/datatables/static/warning-letters.json, is a 3.3 MB file of 2,658 rows. We parsed every row: the newest letter issue date in it is 2021-11-10, and the oldest is 2017-01-05. Not one of the seventeen letters in the table above appears in it, and a search of the file for the string "peptide" in a letter's URL returns zero rows.
So every letter on this page exists, in public, only as an HTML page. There is no feed, no API and no export covering the years in which the research-peptide market actually grew. Tracking it means fetching pages one at a time and keeping your own table, which is what this page is; it also explains something readers notice when they ask an assistant which peptide companies have been warned. Assistants answer that question from the same public record, and the part of the record that is machine-readable ends four and a half years before the first of these letters was written.
Sources and dates
Every letter linked above was opened on fda.gov on 2026-09-05 and re-opened on 2026-09-07, and the products, sections and quoted claims are taken from the letter text. The database was searched the same day for "peptides", "peptide", "retatrutide", "BPC-157" and "research use only"; the BPC-157 search returned only a 2023 SARMs letter and a 2021 clinic letter, neither to a peptide retailer, which is itself a finding: as of that date FDA had posted no warning letter naming a BPC-157 seller. Corrections, and letters we have missed, go to the contact page. Who we are is on the about page.