Where sources disagree

Retatrutide (LY3437943) is described by its developers' phase 2 trial as an agonist of three receptors: the glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide 1 (GLP-1) and glucagon receptors.

Jastreboff, Kaplan, Frías et al. (Retatrutide Phase 2 Obesity Trial Investigators) · Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial · 2023-08

FDA identified a product sold as "GLP-3R" as retatrutide and listed it among unapproved new drugs offered by the website.

FDA · Peak Performance Peptides warning letter (MARCS-CMS 735127) · 2026-08

FDA noted that another firm referred to retatrutide as "GLP-1-R peptide" and to tirzepatide as "GLP-2 peptide", and treated both as unapproved new drugs.

FDA · Gram Peptides warning letter (MARCS-CMS 721806) · 2026-03

Glucagon-like peptide-2 is a natural 33-amino-acid hormone derived from proglucagon, secreted by gut L cells and acting through its own receptor in the gastrointestinal tract, which makes 'GLP-2' a misleading label for tirzepatide.

Drucker and Yusta (University of Toronto) · Physiology and pharmacology of the enteroendocrine hormone glucagon-like peptide-2 · 2014

Seller labeling quoted in FDA's August 2026 warning letter used 'GLP-3R' as the product name and described it as a synthetic peptide acting as "a multi-receptor agonist targeting GIP, GLP-1, and glucagon receptors in research settings", with FDA supplying the INN retatrutide in brackets.

A US online research-peptide seller, as quoted by FDA · Peak Performance Peptides warning letter (MARCS-CMS 735127) · 2026-08

FDA's current compounding page lists BPC-157 among substances once placed in 'category 2' whose nominations were withdrawn by the nominators; it is not in the active category 2 table. FDA's stated concern is immunogenicity risk and a lack of safety information.

FDA · Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (page updated April 2026) · 2026-04

A peer-reviewed narrative review says the lack of human evidence 'has led both the FDA and WADA to restrict BPC-157'.

Authors of 'Regeneration or Risk?' narrative review · Regeneration or Risk? A Narrative Review of BPC-157 for Musculoskeletal Healing

Press coverage reports HHS Secretary Robert F. Kennedy Jr. saying FDA may move 14 peptides that compounders were previously barred from making off a banned list, while acknowledging there is no robust scientific data supporting their use.

Korin Miller (SELF) · RFK Jr. Wants to Un-ban 14 Peptides. What Doctors Want You to Know · 2026-03

A review concludes GHK-Cu has regenerative and protective actions and cites clinical studies of facial and eye creams in women with photoaged skin; it also reviews systemic effects seen in rodents and pigs. The review carries a formal declaration of no conflict of interest; the authors’ stated affiliation is their own copper-peptide skincare company, and the lead author is the discoverer of the molecule.

Loren Pickart and Anna Margolina · Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data · 2018-07

For injectable GHK-Cu, FDA flags immunogenicity risk from aggregation and impurities and says there are limited data in humans to inform safety.

FDA · Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks · 2026-04

The originating group reported that epithalon induced telomerase activity and telomere elongation in cultured human somatic cells.

Khavinson et al. · Epithalon peptide induces telomerase activity and telomere elongation in human somatic cells · 2003-06

In the originating group's own mouse study, epithalon did not change mean life span, but raised the life span of the longest-lived 10% of survivors and the maximum life span, and did not change total tumor incidence.

Anisimov, Khavinson et al. · Effect of Epitalon on biomarkers of aging, life span and spontaneous tumor incidence in female Swiss-derived SHR mice · 2003

A UK university lab says earlier work lacked a comprehensive quantitative study, and reports that epithalon lengthened telomeres in human cell lines via telomerase upregulation or ALT activity. This is cell-line work, not a lifespan study.

Sarah Al-dulaimi, Ross Thomas, Sheila Matta, Terry Roberts (Brunel University London) · Epitalon increases telomere length in human cell lines through telomerase upregulation or ALT activity · 2025-09

FDA has not identified safety information for epithalon's proposed route and says it lacks sufficient information to know whether it would cause harm in humans.

FDA · Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks · 2026-04

FDA determined the tirzepatide injection shortage resolved on December 19, 2024 and the semaglutide injection shortage resolved on February 21, 2025, and set enforcement-discretion deadlines for compounders afterwards (for outsourcing facilities and semaglutide, until May 22, 2025).

FDA · FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize · 2025-02

The compounders' trade group called the semaglutide decision 'reckless and arbitrary' and said it denied the public access to needed medicine; a federal district judge sided with FDA and denied the injunction.

Outsourcing Facilities Association, as reported by BioSpace · Judge Rules Against Semaglutide Compounders After Shortage Declared Over · 2025-04

FDA staff told its compounding advisory committee that Ta1 is not approved in the United States, Japan, or Europe (except Italy), and that FDA could not independently verify the manufacturer's claims of approval in all the countries listed.

FDA · Thymosin Alpha-1 (Ta1) Related Bulk Drug Substances (Pharmacy Compounding Advisory Committee briefing) · 2024-12

A published review states that thymalfasin is 'approved in more than 35 countries' for hepatitis B and C and as an immune enhancer. The statement is cited to a 2015 historical review, and the authors declare no conflicts.

Dominari, Hathaway et al. · Thymosin alpha 1: A comprehensive review of the literature · 2020-12

A randomized, double-blind, placebo-controlled study of CJC-1295, a long-acting GHRH analog, found sustained GH and IGF-I increases with an estimated half-life of 5.8 to 8.1 days and no serious adverse reactions in healthy adults.

Teichman, Neale, Lawrence, Gagnon, Castaigne, Frohman · Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults · 2006-03

FDA reports serious adverse events associated with CJC-1295, including increased heart rate and a systemic vasodilatory reaction, and says the available clinical data are limited.

FDA · Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks · 2026-04

A community reference site states that 'no-DAC' (Mod GRF 1-29) is a different, short-acting molecule with no completed trials of its own, that its human data are extrapolated from other analogs, and that products are frequently mislabeled or substituted between the two forms.

peptideschedule.com (community reference) · CJC-1295 No DAC: Science vs Community Consensus

After reviewing trials, post-marketing data and literature, EMA's safety committee concluded NAION is a very rare side effect of semaglutide medicines; large epidemiological studies suggest roughly a two-fold relative risk in adults with type 2 diabetes, about one extra case per 10,000 person-years.

EMA PRAC · PRAC concludes eye condition NAION is a very rare side effect of semaglutide medicines · 2025-06

A consensus statement says many studies report a small possible increased risk, but some report no correlation, including a meta-analysis of 69 randomized trials that found no association and a military claims-data study that found lower risk in people with diabetes. Overall magnitude of risk remains low.

NANOS and the American Academy of Ophthalmology · GLP-1 Receptor Agonists and the Risk of NAION: A Consensus Statement by NANOS and the AAO · 2026-05

Argued that most weight lost on GLP-1 drugs is fat, that lean mass contributes a proportion typical of any weight loss, that there is no evidence these drugs cause frailty or sarcopenia, and that weight loss improves muscle quality and function.

Samuel Klein, MD · Should We Be Concerned About Muscle Loss With GLP-1s? (ADA 2026 debate) · 2026-07

Agreed there is little evidence of harm in otherwise healthy people but said older patients, women in menopause, and people with sarcopenic obesity warrant worry because excessive muscle loss can affect strength, balance and bone, raising frailty and fracture risk.

Eric Ravussin · Should We Be Concerned About Muscle Loss With GLP-1s? (ADA 2026 debate) · 2026-07

A review of the clinical literature says lean mass typically accounts for about a quarter of weight lost, comparable to other weight-loss approaches, but that the incidence of clinically significant muscle wasting attributable to GLP-1 therapy remains undefined.

Authors of 'Muscle loss and GLP-1R agonists use' · Muscle loss and GLP-1R agonists use

In the TRIUMPH-4 phase 3 readout, Lilly reported dysesthesia in 8.8% and 20.9% of patients in the lower and higher dose arms versus 0.7% on placebo; Lilly said the events did not seem to lead to discontinuation. BioSpace describes it as a new safety signal not reported in the earlier mid-stage trial.

Annalee Armstrong (BioSpace), reporting Lilly's results · Lilly's Retatrutide Scores Triple Trial Triumph With 26% Weight Loss, But New Safety Signal Emerges · 2025-12

A pharmacovigilance and literature review notes that in the phase 2 retatrutide trial, cutaneous hyperesthesia and skin sensitivity adverse events were reported in 7% of retatrutide participants versus 1% on placebo, in a dose-dependent pattern, and reviews dysesthesia reports across GLP-1 drugs.

Laroche, Geniaux, Jardou · Dysesthesia associated with GLP-1 agonist therapies: data-mining analysis and literature review · 2026-05

FDA says retatrutide cannot be used in compounding under federal law and has not been found safe and effective for any condition; it has warned telehealth companies and API suppliers over retatrutide.

FDA · FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss · 2026-10

Stability testing provides evidence on how a drug's quality changes over time under temperature, humidity and light, and is used to set a retest period or shelf life. Formal data should cover at least three primary batches; for a substance stored in a freezer, at least 12 months of long-term data at -20 °C is expected at submission.

ICH, as adopted by FDA · Q1A(R2) Stability Testing of New Drug Substances and Products · 2003-11

Solid peptides still degrade by deamidation, peptide bond cleavage, oxidation and aggregation, and the rate depends on temperature, moisture content, excipients and whether the solid is amorphous or crystalline, so stability is specific to the material and formulation.

Lai and Topp (University of Kansas) · Solid-state chemical stability of proteins and peptides · 1999-05

A seller's guide states that freeze-dried peptides stay stable for 2 to 5 years frozen at -20 °C and 12 to 24 months in a fridge, supporting the range with reagent suppliers' general statements and published studies of other molecules rather than with batch stability data for its own products.

A US online research-peptide seller (analytical team blog) · How Long Do Peptides Last in Powder Form? Shelf Life Data · 2026-08

FDA determined that Geref (sermorelin acetate) was not withdrawn from sale for reasons of safety or effectiveness. The maker discontinued it in 2008; its approvals covered idiopathic growth hormone deficiency in children and a diagnostic use.

FDA · Determination That GEREF (Sermorelin Acetate) Injection ... Were Not Withdrawn From Sale for Reasons of Safety or Effectiveness (78 FR 14095) · 2013-03

TIME describes sermorelin as previously approved to treat children with growth hormone deficiency, now sold through compounding pharmacies, with people taking it for muscle growth and fat loss.

Dominique Mosbergen (TIME) · What to Know About the 'Anti-Aging' Peptide Shots Flooding Social Media · 2026-02

FDA lists 'Thymosin beta-4, fragment (LKKTETQ), also known as TB-500' and says it has not identified any human exposure data for this fragment.

FDA · Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks · 2026-04

Anti-doping chemists identified the N-terminal acetylated 17-23 fragment of human thymosin beta-4 (Ac-LKKTETQ) in a TB-500 product, i.e. a seven-residue fragment rather than the full protein.

Esposito, Deventer, Goeman, Van der Eycken, Van Eenoo · Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential · 2012-09

A 2026 scoping review treats 'TB-500' as a commercial designation whose meaning varies across commercial, regulatory and research contexts; most included studies evaluated thymosin beta-4, and direct TB-500 evidence was limited to a single study.

McGuire, Hughes, Maak, Cushman · Thymosin Beta-4 and TB-500 in Tissue Healing, Regeneration, and Musculoskeletal Repair: A Scoping Review · 2026-06

A community forum post says TB-500 and thymosin beta-4 get used interchangeably online, and that most studies cited for 'TB-500' were run on thymosin beta-4.

Reddit user, r/NTNPerformance · Peptide TB-500 vs TB-4: Why the Thing in the Vial Often Isn't ...

FDA warning letters say that despite 'research use only' and 'not for human consumption' statements on labeling, evidence from the seller's website establishes that the products are intended as drugs for human use.

FDA · Peak Performance Peptides warning letter (735127) · 2026-08

FDA's GLP-1 page says it has warned companies that sold semaglutide, tirzepatide, retatrutide, survodutide or mazdutide falsely labeled 'for research purposes' or 'not for human consumption' directly to consumers with dosing instructions.

FDA · FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss · 2026-10

A review argues the 'research use only' label is especially problematic because it may shift liability away from vendors while products circulate among consumers who discuss self-administration.

Authors of 'Unregulated Peptide Use in the Age of Biohacking' · Unregulated Peptide Use in the Age of Biohacking: Digital Promotion, Gray-Market Access, and Emerging Public Health Risks

Sellers' labeling presents the products as laboratory materials not intended for people, which they treat as sufficient. FDA's letters quote these exact labels and reject them (USApeptide.com letter).

Sellers, as quoted in an FDA warning letter · USApeptide.com warning letter (MARCS-CMS 696885) · 2025-02

A test-purchase study of semaglutide vials from online sellers found measured purity of 7.7% to 14.37% against the 99% claimed, content above the labeled amount by 28.56% to 38.69%, and endotoxin in every sample; all vials were judged probable substandard or falsified products.

Ashraf, Mackey, Vida, Kulcsar, Schmidt, et al. · Multifactor Quality and Safety Analysis of Semaglutide Products Sold by Online Sellers Without a Prescription · 2024-11

FDA warns that illegally marketed GLP-1 products may contain the wrong ingredients, harmful ingredients, or too little, too much or no active ingredient at all.

FDA · FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss · 2026-10

A peptide-testing laboratory's guide says HPLC purity and content are different measures: a sample 100% pure by HPLC may be only 70 to 85% peptide by mass because of bound counterions, water and solvents.

Vanguard Laboratory (testing-services guide) · The Ultimate Guide to HPLC Testing for Peptides

FDA says compounded GLP-1 drugs are not FDA approved and are not reviewed for safety, effectiveness or quality; it lists claims that a compounded drug is 'the same as' an approved drug as a telehealth red flag, and reports dosing-error adverse events, some requiring hospitalization. As of May 31, 2026 it had 990 adverse-event reports for compounded semaglutide and over 730 for compounded tirzepatide.

FDA · FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss · 2026-10

FDA warning letters cite telehealth sites that advertised compounded products as having the 'same active ingredient as Ozempic and Wegovy' or 'as Mounjaro and Zepbound'.

FDA · Remedy Meds warning letter (MARCS-CMS 716830) · 2025-09

Press coverage reports FDA sent more than 50 warning letters to telehealth firms for false or misleading claims implying compounded products were approved or equivalent.

Katie Palmer (STAT) · FDA warns telehealth providers over obesity drug marketing · 2025-09

FDA cites published case reports of serious adverse events with melanotan II, including melanoma, posterior reversible encephalopathy syndrome, sympathomimetic toxidrome and priapism, plus an immunogenicity risk.

FDA · Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks · 2026-04

Australia's TGA says melanotan is not approved for tanning, has not been assessed for quality or safety, and that melanotan II has been linked to increased moles and freckles, kidney dysfunction and brain swelling. TGA also notes promoters often claim the products are safe and natural.

TGA · Don't risk using tanning products containing melanotan · 2025-01

A UNSW medical expert says case reports describe melanomas emerging from existing moles during or shortly after melanotan II use, and warns about social-media advertising.

Prof. Bernard Stewart · What is Melanotan-II - the drug that the TGA urges consumers to avoid? · 2023-01

Online promoters present injectable and nasal melanotan products as a safe, natural way to tan without the sun (as characterised by the TGA).

Online promoters, as described by TGA · Don't risk using tanning products containing melanotan · 2025-01

A systematic review of BPC-157 in orthopaedic sports medicine found the literature to be almost entirely preclinical, with a single small human study (knee pain, subjective follow-up survey) and no controlled human trials.

Authors of the HSS Journal systematic review · Emerging Use of BPC-157 in Orthopaedic Sports Medicine: A Systematic Review · 2025

A narrative review calls human data 'exceedingly sparse' and describes only three published human studies, one an open-label knee-pain trial.

Authors of 'Regeneration or Risk?' narrative review · Regeneration or Risk? A Narrative Review of BPC-157 for Musculoskeletal Healing

FDA's compounding review found no or only limited safety information for the proposed routes and said it lacks sufficient information to know whether BPC-157 would cause harm in humans.

FDA · Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks · 2026-04

Popular promotion presents BPC-157 as a 'Wolverine peptide' that heals tendon, muscle, gut and nerve tissue; clinicians interviewed say there is almost no human trial evidence behind that framing.

Promoters, as described by UCHealth Today · Peptides: Doctors explain the benefits, risks and FDA concerns