GIP / GLP-1 / Glucagon receptor agonist · Investigational · Weekly subcutaneous
Retatrutide: the triple-agonist redefining the weight-loss ceiling.
Retatrutide is an investigational once-weekly agonist of three metabolic receptors — GIP, GLP-1, and glucagon. Phase 2 data showed mean weight loss of 24.2% at 48 weeks at the highest dose, exceeding any pharmacologic agent in clinical development. Phase 3 (TRIUMPH program) is ongoing through 2025–2026.
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What Retatrutide is
Retatrutide is an investigational synthetic peptide developed by Eli Lilly with balanced agonism at the GIP, GLP-1, and glucagon receptors. It adds glucagon activity to the dual-agonist architecture pioneered by tirzepatide.
It is NOT FDA-approved. Phase 3 trials (TRIUMPH-1 through TRIUMPH-4) in obesity, type 2 diabetes, knee osteoarthritis, and obesity with cardiovascular risk are enrolling or ongoing through 2025–2026.
There is no legal U.S. commercial supply outside of clinical trials. Compounded retatrutide is not a permitted §503A product and is not part of legitimate U.S. clinical care.
How it works
GLP-1 receptor activation drives the familiar incretin effects: glucose-dependent insulin secretion, glucagon suppression, slowed gastric emptying, reduced appetite.
GIP receptor activation contributes additional central appetite suppression and may improve adipose-tissue lipid handling. Together these reproduce the tirzepatide profile.
Glucagon receptor activation — the third agonist — modestly increases resting energy expenditure and promotes hepatic fat oxidation. This appears to be the key contributor to retatrutide's superior weight-loss magnitude.
What patients use it for
Highest weight loss seen in any incretin trial
Phase 2 (Jastreboff AM et al., NEJM 2023): 24.2% mean body-weight reduction at 12 mg over 48 weeks — exceeding tirzepatide and semaglutide trial benchmarks.
Improved glycemic control
Phase 2 in type 2 diabetes: HbA1c reductions of ~2.0% — competitive with the best incretin therapies in class.
Reduction in hepatic fat
Phase 2 NAFLD analyses showed substantial reduction in liver fat content — likely driven by the glucagon-receptor arm.
Triple-mechanism architecture
Combining incretin + glucagon receptor activity provides both reduced energy intake and modestly increased energy expenditure — a pharmacologically novel weight-loss profile.
Evidence summary
Jastreboff AM et al. (NEJM 2023): Phase 2 obesity trial showing 24.2% mean weight loss at 12 mg/48 wk — the headline result that established retatrutide as the leading candidate to surpass tirzepatide.
Rosenstock J et al. (Lancet 2023): Phase 2 type 2 diabetes trial showing HbA1c reductions of up to 2.0%.
TRIUMPH-1 (obesity), TRIUMPH-2 (T2D), TRIUMPH-3 (knee OA with obesity), TRIUMPH-4 (obesity with CVD) — Phase 3 program enrolling/ongoing through 2025–2026.
Dosing and clinical context
General clinical context only. Kindr Health physicians determine the appropriate dose and protocol for each patient based on history and labs. This is not a prescription or dosing recommendation.
Phase 2 dose range: 1 mg, 4 mg, 8 mg, 12 mg weekly subcutaneous, with gradual titration starting at 2 mg.
There is no FDA-approved dose because the drug is not approved. Trial titration protocols are not a substitute for FDA labeling.
Outside of clinical-trial participation, retatrutide is not legally available in the U.S. Patients interested in trials can search clinicaltrials.gov for active TRIUMPH sites.
Safety and contraindications
Most common side effects in Phase 2 were GI: nausea, diarrhea, vomiting, constipation — comparable in profile to other incretins. Mostly titration-dependent.
Glucagon receptor activity introduces additional considerations: transient increases in heart rate, transient ALT elevations, and small increases in fasting glucose at higher doses in some subgroups.
No long-term human safety data yet. The Phase 3 program is designed to characterize long-term safety, including cardiovascular, hepatic, and pancreatic endpoints.
Not appropriate in pregnancy. Not appropriate in medullary thyroid carcinoma or MEN-2 by class precaution.
Who it's typically considered for
- Adults with severe obesity who are willing to consider clinical-trial participation
- Patients who have plateaued on semaglutide or tirzepatide and want exposure to next-generation mechanism — through a trial
- Patients seeking peer-reviewed evidence to inform future treatment decisions when retatrutide approves
- NOT appropriate for off-label compounded use — there is no legitimate U.S. commercial supply chain
Frequently asked questions
Can I get retatrutide from a compounding pharmacy?
No. Retatrutide is an investigational drug and was never on an FDA shortage list. It is not eligible for §503A compounding. Internet "retatrutide" supply is not legitimate U.S. clinical care.
When will retatrutide be FDA-approved?
Eli Lilly's Phase 3 TRIUMPH program is expected to read out through 2025–2026. Realistic earliest U.S. approval is 2026, with broad commercial availability following.
How much more effective is retatrutide vs tirzepatide?
Phase 2 retatrutide showed 24.2% weight loss at 12 mg/48 wk. SURMOUNT-1 tirzepatide showed 20.9% at 15 mg/72 wk. The magnitudes suggest retatrutide is the more potent agent — but this awaits direct head-to-head Phase 3 confirmation.
What does the glucagon receptor add?
Glucagon receptor activity modestly increases resting energy expenditure and promotes hepatic fat oxidation. It is the mechanism most likely responsible for retatrutide's edge over dual agonists.
Why does retatrutide reduce liver fat so much?
Glucagon-receptor activation directly drives hepatic fat oxidation. Combined with the weight-loss-mediated metabolic benefit, retatrutide produces substantial reductions in hepatic fat content in early studies.
Is retatrutide safe for diabetes?
Phase 2 data in type 2 diabetes look favorable, but the glucagon arm raises specific monitoring needs around glycemic variability and liver enzymes. Phase 3 will define the long-term picture.
Can I participate in a retatrutide trial?
Yes — search clinicaltrials.gov for active TRIUMPH sites. Enrollment criteria vary by trial; your clinician can help review eligibility.
How does retatrutide compare to bariatric surgery?
Mean Roux-en-Y gastric bypass weight loss is ~30% at 1 year. Phase 2 retatrutide at 24% approaches surgical benchmarks pharmacologically — without the procedural risk profile.
Sources
- Jastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. NEJM (2023). — pubmed.ncbi.nlm.nih.gov/37366315
- Rosenstock J et al. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial. Lancet (2023). — pubmed.ncbi.nlm.nih.gov/37385275
- TRIUMPH Phase 3 program — ClinicalTrials.gov. — clinicaltrials.gov/search?term=retatrutide&aggFilters=phase:3
- Eli Lilly investor materials — retatrutide development update. — investor.lilly.com
Considering Retatrutide?
A Kindr Health physician reviews every longevity intake — peptides are prescribed only when medically indicated based on your history and labs. There is no charge for the initial review.
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Medically reviewed by Kindr Health Clinical Team
Kindr Health Inc. — Editorial & Clinical Team (physician-supervised)
NPI 1609792902 · Last reviewed: July 3, 2026
Last reviewed July 3, 2026. Compounded medications are prepared by FDA-registered 503A pharmacies and are not FDA-approved drug products. Prescriptions require a clinical evaluation; a Kindr Health physician determines eligibility. Not for use in pregnancy. This page provides educational information and is not medical advice.