What is the difference between retatrutide and tirzepatide?

Retatrutide is an investigational triple agonist studied for activity at GIP, GLP-1, and glucagon receptors. Tirzepatide is a dual GIP and GLP-1 receptor agonist available in FDA-approved medications. This page is educational only and does not compare medications for personal treatment decisions.

Is retatrutide FDA approved?

No. Retatrutide is investigational and is not FDA approved for consumer use. Reta Support does not provide sourcing, dosing, prescribing, or treatment guidance.

Is tirzepatide FDA approved?

Tirzepatide is the active ingredient in FDA-approved prescription medications for certain approved uses. Questions about medication use, eligibility, risks, symptoms, side effects, or treatment decisions should be discussed with a licensed healthcare provider.

Can RetaTracker track retatrutide-related notes?

RetaTracker can help users organize personal notes, symptoms, food noise, injection dates, provider questions, and progress observations. It does not provide dosing guidance, medication instructions, safety claims, or treatment recommendations.

Does Reta Support give medication advice?

No. Reta Support provides educational tracking tools and personal organization resources only. It does not provide medical advice, diagnosis, treatment, prescribing guidance, dosing guidance, pharmacy guidance, medication sourcing, or emergency care.

GLP-1 Medication Comparison

Retatrutide vs Tirzepatide — Full GLP-1 Comparison

The retatrutide vs tirzepatide comparison below is built from publicly available clinical trial data and published research. Retatrutide and tirzepatide are both developed by Eli Lilly, but they are different agents. Retatrutide is an investigational GIP, GLP-1, and glucagon triple receptor agonist, while tirzepatide is an FDA-approved GIP and GLP-1 dual receptor agonist. They also differ in regulatory status, clinical-trial programs, and availability. Use this retatrutide vs tirzepatide reference to organize your questions before speaking with your own healthcare provider.

Last reviewed: September 26, 2026 · Updated with July 2026 TRIUMPH-2 and TRIUMPH-3 Phase 3 topline results · Primary sources: NEJM, Eli Lilly, ClinicalTrials.gov

Quick Answer — Retatrutide vs Tirzepatide

Retatrutide is an investigational triple agonist (GLP-1 + GIP + glucagon) with results now reported from multiple Phase 3 studies. Tirzepatide is a dual agonist (GLP-1 + GIP) that is FDA-approved as Mounjaro and Zepbound and commercially available by prescription. Results from separate retatrutide and tirzepatide trials should not be interpreted as a head-to-head comparison or as evidence that one medication is superior to the other. The studies differ in populations, durations, doses, endpoints, estimands, and protocols. Appropriate head-to-head evidence is needed for direct comparative conclusions. On July 23, 2026, Lilly announced Phase 3 topline results from TRIUMPH-2 and TRIUMPH-3 and said it plans a U.S. Biologics License Application submission in Q1 2027. Lilly continues to state that retatrutide is investigational and has not been approved by any regulatory agency. Tirzepatide is FDA-approved and commercially available by prescription.

Retatrutide vs Tirzepatide — Interactive Comparison Tool

Filter by category to explore specific aspects of the retatrutide vs tirzepatide comparison — mechanism, trial results, side effects, or FDA status. This comparison uses peer-reviewed research, clinical-trial registries, regulatory materials, and official sponsor-reported trial results. Sponsor-reported topline results are identified as such and should be distinguished from fully published peer-reviewed results.

What it is

A triple hormone receptor agonist that targets GLP-1, GIP, and glucagon receptors. Retatrutide remains investigational. Lilly has disclosed results from five Phase 3 retatrutide trials and has announced plans for a U.S. BLA submission in Q1 2027.

A dual hormone receptor agonist that targets GLP-1 and GIP receptors. Tirzepatide is FDA-approved under the brand names Mounjaro and Zepbound.

Developer

Eli Lilly and Company

Administration

Once-weekly subcutaneous injection in clinical trials

Once-weekly subcutaneous injection by prescription

Receptors targeted

Triple agonist
GLP-1, GIP, and glucagon receptors. The glucagon receptor component is a major difference in the retatrutide vs tirzepatide comparison.

Dual agonist
GLP-1 and GIP receptors only, without glucagon receptor activation.

Glucagon receptor activity

Yes. Retatrutide's glucagon receptor activity is part of its distinct mechanism, but mechanism alone does not establish greater clinical effectiveness than tirzepatide.

No. Tirzepatide does not include glucagon receptor agonism.

Selected weight-loss trial results — not head-to-head

Lilly-reported Phase 3 results include up to 20.8% average weight reduction at 80 weeks in TRIUMPH-2 among adults with obesity or overweight and type 2 diabetes, and up to 22.6% at 80 weeks in TRIUMPH-3 among adults with severe obesity and established cardiovascular disease, with or without type 2 diabetes. TRIUMPH-4 previously reported 28.7% at 68 weeks in adults with obesity or overweight and knee osteoarthritis. These results come from separate studies and are not head-to-head comparisons.

SURMOUNT-1 reported mean body weight reduction up to 20.9% at 72 weeks in adults with obesity or overweight without diabetes. Because SURMOUNT-1 and the retatrutide TRIUMPH trials used different populations, durations, doses, endpoints, and protocols, these percentages cannot establish comparative superiority.

Trial stage

Phase 3 clinical development

Approved medication with large Phase 3 trial data and post-market use

Other noted effects

TRIUMPH-4 also reported improvements in WOMAC pain and physical function in people with knee osteoarthritis, along with cardiometabolic improvements.

Tirzepatide has shown improvements in blood sugar, HbA1c, cardiometabolic markers, and weight-management outcomes across multiple trials.

Common side effects

Nausea, vomiting, diarrhea, constipation, and decreased appetite are commonly reported during dose escalation in trial participants.

Nausea, vomiting, diarrhea, constipation, and decreased appetite are also common, especially during dose initiation and escalation.

Long-term safety data

Safety follow-up continues through the retatrutide clinical-development program because retatrutide remains investigational.

Tirzepatide has clinical-trial and post-marketing safety data following FDA approval.

FDA approval status

Not FDA-approved. Retatrutide remains investigational and has not been approved by any regulatory agency. Lilly has announced plans to submit a U.S. Biologics License Application in Q1 2027.

FDA-approved. Tirzepatide is approved as Mounjaro for type 2 diabetes and Zepbound for chronic weight management.

Availability

Not commercially available. Any online “retatrutide peptide” listings should not be treated as equivalent to regulated clinical-trial drug supply.

Commercially available by prescription through licensed healthcare providers and approved dispensing channels.

Can I get it now?

Only through participation in an active clinical trial, if eligible.

Yes, if prescribed by a licensed healthcare provider and clinically appropriate.

Retatrutide vs tirzepatide — data source note: This comparison includes published and publicly released data from Phase 2 and Phase 3 programs, including the NEJM retatrutide Phase 2 paper, Eli Lilly TRIUMPH-4 results, and SURMOUNT-1 tirzepatide results. Trial figures represent group averages from different study populations and do not predict individual outcomes. Cross-trial percentages cannot establish comparative superiority because populations, durations, doses, endpoints, estimands, and protocols differ. Direct comparative conclusions require appropriate head-to-head evidence. Last reviewed: September 26, 2026.

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Primary sources

Sources & outbound links

These are the primary external sources used for this retatrutide vs tirzepatide comparison. They open in a new tab.

Retatrutide Phase 2 trial — New England Journal of Medicine

Peer-reviewed Phase 2 trial data on retatrutide in adults with obesity.

View source

TRIUMPH-4 Phase 3 topline results — Eli Lilly

Company press release summarizing Phase 3 retatrutide results in obesity and knee osteoarthritis.

View source

SURMOUNT-1 tirzepatide trial — New England Journal of Medicine

Peer-reviewed Phase 3 trial results for tirzepatide in adults with obesity or overweight.

View source

ClinicalTrials.gov

Registry source for ongoing retatrutide and tirzepatide clinical trials and study details.

View source

Mounjaro prescribing information

FDA-approved prescribing information for tirzepatide as Mounjaro.

View source

Zepbound prescribing information

FDA-approved prescribing information for tirzepatide as Zepbound.

View source

Full disclaimer — retatrutide vs tirzepatide comparison

This retatrutide vs tirzepatide comparison tool is provided by ABX Apps for educational and informational purposes only. The information presented is compiled from publicly available clinical trial data, peer-reviewed research, and published regulatory materials. ABX Apps does not sell, prescribe, source, or recommend any medication, including retatrutide or tirzepatide.

Nothing on this page constitutes medical advice, diagnosis, or a treatment recommendation. Individual results vary. Trial data reflects averages across study populations and may not apply to any one individual.

Retatrutide is an investigational drug that is not approved by the FDA. It is not legally available for routine purchase or use outside authorized clinical trials.

Always consult a qualified, licensed healthcare provider before making decisions about medications, side effects, dose changes, or clinical trial participation.

Editorial disclosure — RetaSupport

This retatrutide vs tirzepatide page is written and maintained by a licensed clinical social worker who is also a personal GLP-1 user. All clinical data referenced is sourced to primary literature, Eli Lilly materials, and trial registries.

The author’s clinical background informs the behavioral and psychological discussion on topics like food noise, emotional adjustment, and access stress, but this page is not clinical care and should not be treated as healthcare guidance.

ABX Apps does not have a paid commercial relationship with Eli Lilly, Novo Nordisk, or any GLP-1 manufacturer. No sponsored placement appears on this page.