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Comparison

Retatrutide vs Tirzepatide

Both are GLP-1 & incretins, so the meaningful differences are in kinetics, evidence and regulatory status.

On published evidence alone, Tirzepatide is the better documented of the two (regulator approved). That is a statement about the state of the literature, not a recommendation.

Retatrutide Tirzepatide
Class GLP-1 & incretins GLP-1 & incretins
Evidence Clinical trials Regulator approved
Human trials ~8 ~60
Half-life ~6 days ~5 days
Reported range 1-12 mg 2.5-15 mg
Frequency Once weekly (trial protocols) Once weekly, titrated over 20+ weeks
Routes Subcutaneous Subcutaneous
FDA approved No Yes
Research use only Yes No
Banned in sport No No
Studied for Investigational obesity treatment, Type 2 diabetes research, NAFLD research Type 2 diabetes, Chronic weight management, Obstructive sleep apnoea with obesity
Reported side effects Nausea, Vomiting, Diarrhoea, Increased heart rate, Constipation Nausea, Diarrhoea, Vomiting, Constipation, Dyspepsia, Injection-site reactions

Retatrutide

Retatrutide adds glucagon receptor agonism to the GIP and GLP-1 activity of tirzepatide. Glucagon receptor signalling raises energy expenditure and promotes hepatic fat oxidation, which is the proposed reason phase II results exceeded what incretin action alone produces. The phase II trial reported mean weight reduction of around 24% at 48 weeks on the highest dose. As of 2026 it is in Phase 3 (the TRIUMPH program) and is not FDA approved, so no regulatory conclusion on efficacy or safety has been reached.

Tirzepatide

Tirzepatide is a 39-amino-acid synthetic peptide that agonises both the glucose-dependent insulinotropic polypeptide receptor and the GLP-1 receptor, a combination sometimes called a twincretin. GIP receptor activity appears to add to the metabolic effect through adipose tissue and central pathways, and may attenuate some GLP-1-related nausea. A C20 fatty diacid moiety confers albumin binding and weekly dosing. The SURMOUNT programme reported mean weight reductions above 20% at the highest dose, and SURMOUNT-5 showed superiority over semaglutide directly.

Retatrutide vs Tirzepatide: common questions

What is the difference between Retatrutide and Tirzepatide?

Both are GLP-1 & incretins. Retatrutide: An investigational triple agonist at GIP, GLP-1 and glucagon receptors, in Phase 3 trials and not FDA approved. Tirzepatide: A dual GIP and GLP-1 receptor agonist that produced greater weight loss than semaglutide in head-to-head trial data.

Which has stronger evidence, Retatrutide or Tirzepatide?

Tirzepatide has the stronger evidence base (regulator approved, about 60 human studies) compared with Retatrutide (clinical trials).

Are Retatrutide and Tirzepatide FDA approved?

Only Tirzepatide is FDA approved (Type 2 diabetes mellitus (Mounjaro); Chronic weight management (Zepbound); Moderate to severe obstructive sleep apnoea in adults with obesity). Retatrutide is not approved for any indication.

References

Regulatory and primary sources

  1. PubChem compound record (CID 171390338) ↗ · structure, identifiers, synonyms
  2. FDA: Unapproved drugs and "research use only" products ↗ · regulatory status of non-approved products
  3. PubChem compound record (CID 156588324) ↗ · structure, identifiers, synonyms
  4. DailyMed: FDA-approved labeling for Tirzepatide ↗ · indications, dosing, warnings as approved
  5. FDA Drugs@FDA database ↗ · approval history
  6. CAS Registry Number 2023788-19-2 ↗ · chemical identity

Published literature

  1. Jastreboff AM, Kaplan LM, Frías JP, et al.. Triple-Hormone-Receptor Agonist Retatrutide for Obesity - A Phase 2 Trial.N Engl J Med 2023.PubMed 37366315 · doi:10.1056/NEJMoa2301972
  2. Sanyal AJ, Kaplan LM, Frias JP, et al.. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial.Nat Med 2024.PubMed 38858523 · doi:10.1038/s41591-024-03018-2
  3. Misra S, Narayan RK, Kaur M. Efficacy and safety of retatrutide for the treatment of obesity: a systematic review of clinical trials.J Basic Clin Physiol Pharmacol 2025.PubMed 40728138 · doi:10.1515/jbcpp-2025-0113
  4. Katsi V, Koutsopoulos G, Fragoulis C, et al.. Retatrutide-A Game Changer in Obesity Pharmacotherapy.Biomolecules 2025.PubMed 40563436 · doi:10.3390/biom15060796
  5. Locatelli JC, Costa JG, Haynes A, et al.. Incretin-Based Weight Loss Pharmacotherapy: Can Resistance Exercise Optimize Changes in Body Composition?.Diabetes Care 2024.PubMed 38687506 · doi:10.2337/dci23-0100
  6. Moiz A, Filion KB, Toutounchi H, et al.. Efficacy and Safety of Glucagon-Like Peptide-1 Receptor Agonists for Weight Loss Among Adults Without Diabetes : A Systematic Review of Randomized Controlled Trials.Ann Intern Med 2025.PubMed 39761578 · doi:10.7326/ANNALS-24-01590
  7. Panou T, Gouveri E, Popovic DS, et al.. Retatrutide in type 2 diabetes mellitus and obesity: an overview.Expert Rev Clin Pharmacol 2026.PubMed 41785010 · doi:10.1080/17512433.2026.2642415
  8. Drucker DJ. Efficacy and Safety of GLP-1 Medicines for Type 2 Diabetes and Obesity.Diabetes Care 2024.PubMed 38843460 · doi:10.2337/dci24-0003
  9. Jastreboff AM, le Roux CW, Stefanski A, et al.. Tirzepatide for Obesity Treatment and Diabetes Prevention.N Engl J Med 2025.PubMed 39536238 · doi:10.1056/NEJMoa2410819
  10. Jastreboff AM, Aronne LJ, Ahmad NN, et al.. Tirzepatide Once Weekly for the Treatment of Obesity.N Engl J Med 2022.PubMed 35658024 · doi:10.1056/NEJMoa2206038
  11. Aronne LJ, Sattar N, Horn DB, et al.. Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial.JAMA 2024.PubMed 38078870 · doi:10.1001/jama.2023.24945
  12. Malhotra A, Grunstein RR, Fietze I, et al.. Tirzepatide for the Treatment of Obstructive Sleep Apnea and Obesity.N Engl J Med 2024.PubMed 38912654 · doi:10.1056/NEJMoa2404881
  13. Packer M, Zile MR, Kramer CM, et al.. Tirzepatide for Heart Failure with Preserved Ejection Fraction and Obesity.N Engl J Med 2025.PubMed 39555826 · doi:10.1056/NEJMoa2410027
  14. Aronne LJ, Horn DB, le Roux CW, et al.. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity.N Engl J Med 2025.PubMed 40353578 · doi:10.1056/NEJMoa2416394
  15. Look M, Dunn JP, Kushner RF, et al.. Body composition changes during weight reduction with tirzepatide in the SURMOUNT-1 study of adults with obesity or overweight.Diabetes Obes Metab 2025.PubMed 39996356 · doi:10.1111/dom.16275
  16. Frías JP, Davies MJ, Rosenstock J, et al.. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes.N Engl J Med 2021.PubMed 34170647 · doi:10.1056/NEJMoa2107519

Literature retrieved from PubMed on October 16, 2026, favouring human studies and reviews. Numbered markers in the text show which paper supports which statement; uncited entries are background reading.

Read this first This page compares published reference data. It is not medical advice and not a recommendation to use either compound. Several compounds documented on this site are not approved for human use.