Tirzepatide vs Retatrutide

Lilly's approved dual agonist vs its triple agonist still in phase 3

By MoveWell Research Team Updated November 1, 2026

We may earn a commission from links on this page. It never decides our picks. How we make money

Which one for what

Tirzepatide is the only one of the two you can legally get; retatrutide's trial weight loss looks larger, but it hasn't been tested against tirzepatide yet.

  • Any use today: tirzepatide
  • Most weight loss: no head-to-head yet
  • Sleep apnea: tirzepatide
  • Heart risk in diabetes: tirzepatide
  • Retatrutide today: clinical trials only

See all three side by side: Semaglutide vs Tirzepatide vs Retatrutide

Diagram of tirzepatide's label-confirmed changes: Aib at positions 2 and 13, a C20 fatty diacid on Lys20 and a C-terminal amide
TirzepatideGIP + GLP-1 · label changes only; letters not shownTirzepatide guide
Schematic, not a structure: retatrutide activating the GIP, GLP-1 and glucagon receptors
RetatrutideSchematic only: sequence not verified in our sourcesRetatrutide guide
In this guide
  1. Verdict
  2. At a glance
  3. Evidence by goal
  4. Head-to-head trials
  5. Side effects
  6. Key differences
  7. Can you use both?
  8. Where to get each
  9. FAQ
  10. References

At a glance

TirzepatideRetatrutide
What it isGIP and GLP-1 receptor agonist. A peptide based on the GIP sequence, with a fatty diacid that binds albumin1GIP, GLP-1 and glucagon receptor agonist, a "triple agonist"2, 3
StatusFDA-approved: Mounjaro (May 13, 2022) and Zepbound (November 8, 2023)4, 5Not approved anywhere. In phase 3. Lilly plans to submit a Biologics License Application to FDA in Q1 2027 and has given no approval date3, 6
Evidence5/5FDA-approved, with large outcome trials4/5Phase 2 trials and two phase 3 trials published (TRIUMPH-1 in NEJM and TRIUMPH-2 in the Lancet, September 29, 2026). Other phase 3 results are Lilly press releases7, 8
Dosing frequencyWeekly injection only: single-dose pen, single-dose or multi-dose vial, or multi-dose KwikPen1, 9Weekly injection, in clinical trials only. No approved dose10
Oral optionNo. Every labeled form is an injection1, 9No
Self-pay price (US)Zepbound vial or KwikPen $299 to $449 a month by dose, with a refill within 45 days. Mounjaro $499 a month, all doses11, 12No lawful price. Retatrutide sold online is unapproved13
Main side effectsNausea (25% to 29% vs 8% on placebo with Zepbound), diarrhea, vomiting, constipation; hair loss 4% to 5% vs 1%1Nausea (42.4% vs 14.8% at 12 mg in TRIUMPH-1), diarrhea, constipation, vomiting; abnormal skin sensation (dysesthesia)14
Boxed warningSame warning and same contraindication1No label. No boxed warning has been set

Evidence scale: 5 FDA-approved, 4 strong human, 3 limited human, 2 animal or lab only, 1 anecdotal. Prices are self-pay with a prescription, as checked November 1, 2026, and change often.

Retatrutide can't be bought legally. Any retatrutide sold today, including vials labeled "research use only," is unapproved and unlawful to sell for human use. FDA has said compounded retatrutide doesn't qualify for the compounding exemptions and recommends that consumers not buy unapproved products containing it13. It sent warning letters to at least three sellers on December 10, 2024, calling their products "unapproved new drugs" despite research-only labels15, 16, 17. In Aug 2026 Lilly sued six companies it says sold counterfeit retatrutide18, and in Jun 2026 health officials in Victoria, Australia, reported six cases of liver injury across Australia linked to products labeled retatrutide, possibly from a contaminant19. The only legal way to take it is in a clinical trial. See the peptide regulatory tracker for FDA actions.

Evidence by goal

Each goal is graded separately. Approved means an FDA-approved use. Trial data means human trial results but no approval for that use. "No study found" means no data in the sources we reviewed.

GoalTirzepatideRetatrutide
Weight lossApproved5/5Zepbound. SURMOUNT-1 (n=2,539): −20.9% on 15 mg vs −3.1% on placebo at 72 weeks20Trial data4/5TRIUMPH-1 (n=2,339; NEJM): −25.0% on 12 mg vs −3.9% on placebo at 80 weeks7. Lilly's May 2026 press release also gave −28.3% vs −2.2% counting only people who stayed on treatment (efficacy estimand), which makes the gap look larger14
Type 2 diabetesApproved5/5Mounjaro, for adults and children 10 and older9Trial data4/5Phase 2: A1C down up to 2.02 points vs 1.41 on dulaglutide at 24 weeks2. Phase 3: TRIUMPH-2 (n=1,152; Lancet), in obesity with type 2 diabetes: −18.8% body weight on 12 mg vs −5.1% on placebo at 80 weeks, counting everyone who started8; TRANSCEND-T2D-1 and -2 reported by press release21, 6 Press release
Heart attack and stroke riskApproved5/5Mounjaro, in type 2 diabetes at high heart risk (August 28, 2026)22. SURPASS-CVOT vs dulaglutide: HR 0.92, non-inferior; superiority not shown23. Not approved for heart risk without diabetesTrial dataTRIUMPH-3 (n=1,949, established heart disease) included pre-planned heart-event analyses; neither was significant: MACE-5 HR 0.82 (0.55–1.22), MACE-3 HR 1.12 (0.64–1.96). No result from a dedicated heart-outcome trial yet3 Press release
Sleep apneaApproved5/5Zepbound, the first drug approved for sleep apnea (with obesity). Breathing pauses −25.3 vs −5.3 per hour without CPAP24, 25Trial data3/5Limited: one pre-specified TRIUMPH-1 substudy (n=243): apnea-hypopnea index (AHI) fell −31.7 events per hour on 12 mg vs −9.9 on placebo at 80 weeks (NEJM; first presented at ADA, Jun 2026). Not an approved use7, 26
Kidney diseaseNo study foundNo data: no kidney indication9No study foundNo data in the sources we reviewed
MASH (fatty liver)No study foundNo data in the sources we reviewed. Not an approved use1, 9No study foundNo data in the sources we reviewed
Heart failure (HFpEF)Trial data4/5SUMMIT (n=731): heart death or worsening heart failure 9.9% vs 15.3%27. Not approved: Lilly withdrew the US application after FDA asked for another trial28No study foundNo data in the sources we reviewed

Two retatrutide phase 3 trials are peer reviewed: TRIUMPH-1 in NEJM and TRIUMPH-2 in the Lancet, both published September 29, 20267, 8. TRIUMPH-3, TRIUMPH-4 and the TRANSCEND-T2D results are so far Lilly press releases.

Head-to-head trials

  • TRIUMPH-5Retatrutide vs tirzepatideOngoing
    Obesity. No results yet6

Without more direct trials, the best overview is a 2025 review of 26 trials in about 15,491 adults without diabetes. Placebo-adjusted weight loss was about 22% for retatrutide 12 mg (one 48-week phase 2 trial), 18% for tirzepatide 15 mg (72 weeks) and 14% for semaglutide 2.4 mg (68 weeks)29. The trials were too different to pool, so the reviewers ran no combined analysis, and the retatrutide figure predates phase 330.

Numbers from separate trials can't be ranked against each other: lengths (72 and 80 weeks), populations and analysis methods differ.

Side effects

All carry mostly stomach side effects that are worst while the dose is going up. Rates are each drug vs placebo in its own trials, not a head-to-head comparison.

EffectTirzepatideRetatrutide
SourceZepbound 15 mg vs placebo, label112 mg vs placebo, TRIUMPH-114 Press release
Nausea28% vs 8%42.4% vs 14.8%
Diarrhea23% vs 8%32.0% vs 13.5%
Vomiting13% vs 2%25.3% vs 4.8%
Constipation11% vs 5%26.1% vs 10.9%
Stopped for side effects6.2% vs 2.6% (SURMOUNT-1, 15 mg)2011.3% vs 4.9% (TRIUMPH-1, 12 mg)14
Stands outHair loss 4% to 5% vs 1%1Dysesthesia (tingling or touch-sensitive skin): 12.5% vs 0.9% in TRIUMPH-1 and 20.9% at 12 mg in TRIUMPH-414, 31. Heart rate rose early in phase 2, peaking at 24 weeks10

Semaglutide and tirzepatide labels list warnings for serious allergic (hypersensitivity) reactions, pancreatitis, gallbladder disease, low blood sugar (with insulin or insulin secretagogues), kidney injury from dehydration, diabetic eye complications and inhaling stomach contents under anesthesia1.

Key differences

  • Approved vs not. Tirzepatide is FDA-approved as Mounjaro and Zepbound4, 5. Retatrutide is investigational, with a filing planned for Q1 20273.
  • Receptors. Tirzepatide hits GIP and GLP-1 receptors. Retatrutide adds the glucagon receptor1, 2.
  • No head-to-head yet. TRIUMPH-5 is testing retatrutide against tirzepatide; no results yet6. Larger numbers in separate trials can't settle it: lengths, populations and analysis methods differ30.
  • Side effects. Retatrutide has a signal tirzepatide doesn't: dysesthesia, an abnormal skin sensation, in up to 20.9% at 12 mg in one trial31.
  • Where to get it. Tirzepatide is sold through pharmacies and LillyDirect11. Retatrutide can't be bought legally; FDA tells consumers not to buy it13.

Can you use both?

NoNot tested, not legal

Retatrutide isn't approved, so it isn't a legal option alongside tirzepatide. The Zepbound label also says using it with other tirzepatide products or any GLP-1 receptor agonist is not recommended1.

FDA actions on GLP-1 compounding and retatrutide sellers are on the peptide regulatory tracker.

Where to get each

MoveWell sells nothing. Prices as checked November 1, 2026

DrugOptionFormPriceNotes
TirzepatideLillyDirect ZepboundSingle-dose vial or multi-dose KwikPen$299 (2.5 mg), $399 (5 mg), $449 (7.5 to 15 mg) a month with a refill within 45 days; otherwise $499 to $69911Prescription needed. Vials need syringes bought separately. The single-dose pen is for insured patients
TirzepatideLillyDirect MounjaroSingle-dose pen$499 a month, all doses12Prescription needed. For type 2 diabetes
RetatrutideNot available legally. Clinical trials onlyNone approvedNo lawful priceFind a trial on ClinicalTrials.gov. Anything sold today is unapproved and unlawful to sell for human use13, 15

Left off: compounded copies and "research use only" vials. The tirzepatide shortage over in Oct 2024, confirmed December 19, 202432. The Fifth Circuit upheld that decision on August 27, 202633. Routine compounded copies are no longer allowed, and FDA says compounded drugs are not FDA-approved and not the same as generics34. Compounded retatrutide has no lawful path13. More on the regulatory tracker. More options in the Tirzepatide guide.

FAQ

Is retatrutide stronger than tirzepatide?

Unknown. They haven't been compared directly; TRIUMPH-5 is testing that now. Separate trials differ in length, people and analysis, so their numbers can't be lined up.

When will retatrutide be approved?

Lilly plans to submit to FDA in Q1 2027 and hasn't given an approval date.

Can I switch from tirzepatide to retatrutide?

Not legally outside a clinical trial. Retatrutide sold online is unapproved.

Are they made by the same company?

Yes, both are Eli Lilly drugs22, 3.

What side effect is different with retatrutide?

Dysesthesia, an abnormal skin sensation such as tingling, reported in up to 20.9% at 12 mg in one trial. Lilly describes it as mostly mild to moderate.

References

34 sources, with links
  1. FDA. Zepbound (tirzepatide) prescribing information, revised 04/2026. PDF
  2. Rosenstock J et al. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a phase 2 trial. Lancet 2023 (online Jun 26, 2023). doi:10.1016/S0140-6736(23)01053-X. Author PDF
  3. Eli Lilly press release (via BioSpace). TRIUMPH-2 and TRIUMPH-3 topline results; BLA submission planned for Q1 2027 (Jul 23, 2026). Link
  4. BioSpace (FDA release). FDA approves novel, dual-targeted treatment for type 2 diabetes (May 13, 2022). Link
  5. BioSpace (FDA release). FDA approves new medication for chronic weight management (Nov 8, 2023). Link
  6. Eli Lilly press release. TRANSCEND-T2D-2: retatrutide vs Ozempic 2 mg, topline results (Oct 28, 2026). Not peer reviewed. Link
  7. Jastreboff AM, Kaplan LM, Davies MJ et al. Retatrutide, a triple hormone receptor agonist, for treatment of obesity (TRIUMPH-1). NEJM, published online Sep 29, 2026. doi:10.1056/NEJMoa2604169. Summary: GPnotebook
  8. Bellido V, le Roux CW, Ekinci EI et al. Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2). Lancet, published online Sep 29, 2026. doi:10.1016/S0140-6736(26)01861-1. Summary: Cardioteca
  9. FDA. Mounjaro (tirzepatide) prescribing information, revised 08/2026. PDF
  10. Jastreboff AM et al. Triple-hormone-receptor agonist retatrutide for obesity: a phase 2 trial. NEJM 2023 (online Jun 26, 2023). doi:10.1056/NEJMoa2301972. Author PDF
  11. LillyDirect. Zepbound self-pay pricing (page dated Sep 2, 2026; checked Nov 1, 2026). Link
  12. LillyDirect. Mounjaro self-pay pricing (page dated Oct 14, 2026; checked Nov 1, 2026). Link
  13. FDA letter to the Federation of State Medical Boards on retatrutide (Apr 2, 2025), posted by the Arizona Board of Osteopathic Examiners. Link
  14. Eli Lilly press release. TRIUMPH-1 topline results (May 21, 2026). Link
  15. FDA warning letter. Swisschems (Dec 10, 2024). fda.gov
  16. FDA warning letter. Prime Vitality Inc. dba Prime Peptides (Dec 10, 2024). fda.gov
  17. FDA warning letter. Summit Research Peptides (Dec 10, 2024). fda.gov
  18. Healio. Eli Lilly files lawsuits against six companies for allegedly selling retatrutide (Aug 14, 2026). Link
  19. Victoria Department of Health. Toxicity linked to unapproved peptide product labelled retatrutide (Jun 19, 2026). Link
  20. Jastreboff AM et al. Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1). NEJM 2022;387:205–16. Ovid
  21. Eli Lilly press release. TRANSCEND-T2D-1 topline results (Mar 19, 2026). Link
  22. Eli Lilly. FDA approves Lilly's Mounjaro (tirzepatide) to reduce cardiovascular risk (Aug 28, 2026). Link
  23. TCTMD. SURPASS-CVOT published: large trial confirms CVD efficacy of tirzepatide (Nicholls, NEJM 2025;393:2409–20). Link
  24. FDA. FDA approves first medication for obstructive sleep apnea (Dec 20, 2024). fda.gov
  25. American College of Cardiology. SURMOUNT-OSA trial summary (Malhotra, NEJM 2024;391:1193–205). Link
  26. HCPLive. Retatrutide improves weight loss, knee osteoarthritis pain, sleep apnea versus placebo (TRIUMPH-1, NEJM; Sep 29, 2026). Link
  27. American College of Cardiology. SUMMIT trial summary (Packer, NEJM 2024). Link
  28. ConscienHealth. Lilly withdraws tirzepatide application to FDA for heart failure (May 3, 2025). Link
  29. Drugs.com / HealthDay. Some GLP-1s achieve more weight loss than others (on Moiz et al., Ann Intern Med, Jan 2025). Link
  30. TheNNT. Efficacy of tirzepatide, retatrutide and semaglutide for weight loss in obese individuals without diabetes (review of Moiz et al.). Link
  31. Eli Lilly press release. TRIUMPH-4 topline results (Dec 11, 2025). Link
  32. Pharmacy Times. FDA affirms tirzepatide shortage resolved, sets transition period for compounding (Dec 2024). Link
  33. US Court of Appeals for the Fifth Circuit. Outsourcing Facilities Ass'n v. FDA, No. 25-10600 (tirzepatide), unpublished (Aug 27, 2026). PDF
  34. FDA. FDA warns 30 telehealth companies against illegal marketing of compounded GLP-1s (Mar 3, 2026). fda.gov

This page is for education and is not medical advice. Retatrutide is not approved and is available only in clinical trials. Talk to a clinician before starting, stopping or switching any of these drugs.