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Research information only. Not medical advice. 18+ only. Not FDA-approved for human therapeutic use.

Retatrutide

Also known as: LY3437943, triple hormone receptor agonist, GIP/GLP-1/glucagon triple agonist

Synthetic triple receptor agonist peptide (GIP/GLP-1/glucagon receptor agonist)

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What it is

Retatrutide (LY3437943) is a novel synthetic peptide that acts as a triple agonist simultaneously activating three hormone receptors: the glucose-dependent insulinotropic polypeptide receptor (GIPR), the glucagon-like peptide-1 receptor (GLP-1R), and the glucagon receptor (GCGR) (PMIDs: 41090431, 37366315, 57385280). Through GLP-1R agonism, retatrutide increases insulin secretion, suppresses glucagon, slows gastric emptying, and reduces appetite and food intake. GIP receptor agonism provides complementary incretin effects that enhance glycemic control and weight loss. Glucagon receptor agonism promotes energy expenditure and fatty acid oxidation, contributing to additional weight and liver fat reduction (PMIDs: 42858523, 40563436). The molecule increases adenylyl cyclase activity and elevates cyclic AMP (cAMP) levels through all three cognate receptors. In isolated human atrial preparations, retatrutide increased force of contraction in a concentration-dependent manner via cAMP-mediated signaling through GLP-1R, GIPR, and GCGR. Mechanistically, retatrutide also reduces circulating ANGPTL3/8 complex concentrations — an effect attributed to GCGR agonism — which may contribute to reductions in triglycerides and LDL-C. Pharmacokinetic data from Phase 1/2 trials indicate dose-proportional pharmacokinetics and a mean half-life of approximately 6 days, supporting once-weekly dosing.

Class: Synthetic triple receptor agonist peptide (GIP/GLP-1/glucagon receptor agonist)

What it's studied for

  • Obesity / weight management (adults with overweight or obesity without diabetes) Mixed
    • Phase 2 RCT (n=338, 48 weeks, subcutaneous once-weekly). Least-squares mean percentage change in body weight at 48 weeks: -8.7% (1 mg), -17.1% (combined 4 mg), -22.8% (combined 8 mg), -24.2% (12 mg) vs. -2.1% placebo. At 48 weeks, 100% of 8 mg and 12 mg participants achieved ≥5% weight loss; 83% (12 mg) achieved ≥15%. PMID 37366315 Jastreboff AM et al. N Engl J Med. 2023
    • Systematic review: Retatrutide 12 mg once weekly produced weight loss of up to 22.1% (95% CI 19.3%–24.9%) after 48 weeks compared with placebo, exceeding tirzepatide and semaglutide at corresponding follow-up. PMID 39761578 Moiz A et al. Ann Intern Med. 2025
    • Network meta-analysis: retatrutide 12 mg (-22.10% body weight, -17.00 cm waist circumference) and 8 mg (-20.70%, -15.90 cm) were the two most efficacious treatments vs. placebo among GLP-1 receptor agonists and polyagonists assessed. PMID 39305981 Xie Z et al. Metabolism. 2024
    • Bayesian NMA: retatrutide achieved equivalent mean weight loss to dual agonists (-11.0 kg), surpassing GLP-1RAs (-9.0 kg), and excelled at achieving ≥15% weight loss (OR 54.6). Retatrutide had the highest AE risk. PMID 40685589 Sinha B, Ghosal S. Obesity (Silver Spring). 2025
    • Systematic review and meta-analysis of 4 RCTs: 12 mg dose showed the most significant reductions in body weight, BMI, and waist circumference, and the highest proportions achieving ≥5%, ≥10%, ≥15%, and ≥20% weight loss. Safety profile comparable to control. PMID 39817343 Tewari J et al. Expert Rev Clin Pharmacol. 2025
  • Type 2 diabetes mellitus — glycemic control and weight reduction Mixed
    • Phase 2 RCT (n=281, 36 weeks, USA). In people with T2D, retatrutide reduced HbA1c by up to -2.02% (12 mg) vs. -0.01% placebo at 24 weeks. Bodyweight decreased dose-dependently up to -16.94% (12 mg) vs. -3.00% placebo at 36 weeks. Mild-to-moderate GI AEs most common. No severe hypoglycemia or deaths. PMID 37385280 Rosenstock J et al. Lancet. 2023
    • Phase 3 RCT (n=537, 40 weeks, USA/Mexico/India). Retatrutide as monotherapy for T2D inadequately controlled by diet/exercise: mean HbA1c change -1.69% (4 mg), -1.86% (9 mg), -1.94% (12 mg) vs. -0.81% placebo (all p<0.0001). Mean bodyweight change: -11.5% (4 mg), -13.9% (9 mg), -15.3% (12 mg) vs. -2.6% placebo. No sever PMID 42250575 Bajaj HS et al. Lancet. 2026
    • Review: HbA1c decreased by up to 2.16% and fasting glucose by up to 69.1 mg/dL in subjects with T2DM. Weight loss up to 16.94% in T2DM subjects. GI adverse events (nausea, vomiting, constipation, diarrhea) most frequent at highest doses, partly attributable to rapid dose escalation. PMID 41785010 Panou T et al. Expert Rev Clin Pharmacol. 2026
  • Metabolic dysfunction-associated steatotic liver disease (MASLD) / liver fat reduction Mixed
    • Phase 2a RCT substudy (n=98, 48 weeks subcutaneous once-weekly). Mean relative change from baseline in liver fat at 24 weeks: -42.9% (1 mg), -57.0% (4 mg), -81.4% (8 mg), -82.4% (12 mg) vs. +0.3% placebo (all p<0.001 vs. placebo). Normal liver fat (<5%) achieved by 86% (12 mg) vs. 0% placebo at 24 weeks. PMID 38858523 Sanyal AJ et al. Nat Med. 2024
    • Review: retatrutide reduced hepatic fat on MRI-PDFF placebo-subtracted by 81% after 48–72 weeks, the largest reduction reported among semaglutide, tirzepatide, and retatrutide. PMID 40554267 Rodriguez N, Hartmann P. Pharmacol Rev. 2025
    • Systematic review and meta-analysis: among GLP-1RAs studied, retatrutide displayed the most obvious treatment effects on liver fat content reduction. PMID 40489581 Wang Y et al. J Clin Endocrinol Metab. 2025
  • Body composition — fat mass reduction in type 2 diabetes Human RCT
    • Phase 2 body composition substudy (n=189 enrolled, 103 completed, DXA-measured). Percent reduction in total fat mass: 26.1% (8 mg pooled), 23.2% (12 mg), 15.2% (4 mg pooled), 4.9% (0.5 mg) vs. 4.5% placebo and 2.6% dulaglutide. Proportion of lean mass loss to total weight loss was similar to other obesity treatments. PMID 40609566 Coskun T et al. Lancet Diabetes Endocrinol. 2025
  • Blood pressure and lipid profile improvement Human RCT
    • Systematic review and meta-analysis of RCTs: retatrutide significantly decreased systolic BP (WMD -6.79 mmHg, 95% CI -8.36 to -5.23, p<0.0001), diastolic BP (WMD -2.46 mmHg, p<0.0001), total cholesterol (WMD -21.88 mg/dL), LDL-C (WMD -13.10 mg/dL), and triglycerides (WMD -40.90 mg/dL). No significant effect on HDL-C. PMID 42371360 Simental-Mendía LE et al. High Blood Press Cardiovasc Prev. 2026
    • Post-hoc analysis of two phase 2 RCTs: ANGPTL3/8 reductions observed with 8 mg and 12 mg retatrutide in T2D participants and with 1, 4, 8, and 12 mg in participants with obesity/overweight without diabetes. ANGPTL3/8 decreases paralleled TG and LDL-C reductions. In vitro: glucagon and retatrutide decreased ANGPTL3/8 se PMID 40726454 Wen Y et al. Diabetes Obes Metab. 2025
  • Appetite modulation and eating behavior modification Human RCT
    • Phase 2 pre-specified exploratory analysis (n=275, T2D). Retatrutide ≥4 mg vs. placebo: greater reductions in overall appetite, hunger, and prospective food consumption at Week 24 (all p<0.05). At 8 mg and 12 mg: greater improvements in Perceived Hunger and Disinhibition vs. placebo at Weeks 24 and 36. Dietary Restrain PMID 40916752 Kanu C et al. Diabetes Obes Metab. 2025
  • Obstructive sleep apnea (OSA) — Phase 3 investigation Human RCT
    • TRIUMPH Phase 3 program design: OSA protocols nested within TRIUMPH-1 and TRIUMPH-2 weight management basket trials (>5800 total participants). Primary OSA endpoint is change in Apnea-Hypopnea Index. Results not yet reported in this design publication. PMID 41090431 Giblin K et al. Diabetes Obes Metab. 2026
  • Knee osteoarthritis — Phase 3 investigation Human RCT
    • TRIUMPH Phase 3 program design: OA protocols nested in TRIUMPH-1/-2 and a stand-alone OA trial (TRIUMPH-4, >5800 total participants). Primary OA endpoint: change in WOMAC pain subscale score. Results not yet reported. PMID 41090431 Giblin K et al. Diabetes Obes Metab. 2026
  • Chronic kidney disease — Phase 2 investigation Human observational
    • TRANSCEND-CKD Phase 2b mechanistic study (n=146 randomized, eGFR 25–75 mL/min/1.73 m², with/without T2D). Participants randomized 1:1 to once-weekly retatrutide maximum tolerated dose up to 12 mg or placebo. Primary endpoint: change in measured GFR by iohexol clearance at Week 24. Results pending. PMID 41160422 Heerspink HJL et al. Nephrol Dial Transplant. 2026
  • Triple-negative breast cancer (TNBC) in obesity — preclinical investigation Animal studies only
    • Preclinical study: retatrutide inhibited the hexosamine biosynthetic pathway (HBP) and YAP O-GlcNAcylation, leading to increased YAP degradation and decreased tumor size in obese mice bearing TNBC tumors. Enhanced chemotherapy efficacy observed, particularly in obese mice. Mechanism involved EIF3H-mediated deubiquityla PMID 39868848 Cui X et al. Adv Sci. 2025
  • Cardiac inotropic effects — in vitro/ex vivo human tissue In vitro only
    • Ex vivo human right atrial preparations (open heart surgery patients): retatrutide (10–100 nM, cumulative) elevated force of contraction in a concentration- and time-dependent manner via cAMP through GLP-1R, GIPR, and GCGR. Effects diminished by respective receptor antagonists, ryanodine, carbachol, and adenosine recep PMID 40613938 Neumann J et al. Naunyn Schmiedebergs Arch Pharmacol. 2026

Community-reported dosing

RouteDoseFrequency / DurationPopulation / contextSource tier
Subcutaneous injection, once weekly1 mg, 4 mg (initial dose 2 mg or 4 mg), 8 mg (initial dose 2 mg or 4 mg), or 12 mg (initial dose 2 mg) once weekly subcutaneous48 weekshumanResearch PMID 37366315
Subcutaneous injection, once weekly0.5 mg, 4 mg (starting dose 2 mg), 4 mg (no escalation), 8 mg (starting dose 2 mg), 8 mg (starting dose 4 mg), or 12 mg (starting dose 2 mg) once weekly subcutaneous; active comparator: dulaglutide 1.5 mg once weekly36 weekshumanResearch PMID 37385280
Subcutaneous injection, once weekly1 mg, 4 mg, 8 mg, or 12 mg once weekly subcutaneous48 weekshumanResearch PMID 38858523
Subcutaneous injection, once weekly0.5 mg, 4 mg (2 mg initial dose), 4 mg (4 mg initial dose), 8 mg (2 mg initial dose), 8 mg (4 mg initial dose), or 12 mg once weekly subcutaneous36 weekshumanResearch PMID 40609566
Subcutaneous injection, once weekly0.5 mg, 4 mg, 8 mg, or 12 mg once weekly subcutaneous36 weekshumanResearch PMID 40916752
Subcutaneous injection, once weeklyMaximum tolerated dose up to 12 mg once weekly subcutaneous24 weeks (primary endpoint); ongoinghumanResearch PMID 41160422
Subcutaneous injection, once weekly4 mg, 9 mg, or 12 mg once weekly subcutaneous40 weekshumanResearch PMID 42250575
Subcutaneous injection, once weeklyWeekly subcutaneous retatrutide (specific dose not stated in design abstract); compared to placeboPhase 3 multicenter trials (duration not specified in abstract)humanResearch PMID 41090431
In vitro/ex vivo (isolated human atrial preparations)10 nM to 100 nM (cumulative concentrations applied ex vivo)Acute ex vivo experimentin_vitroResearch PMID 40613938
subcutaneous injection2 mgonce weeklybiohackers and self-experimenters pursuing aggressive fat loss / body recomposition[S] Claude Sonnet 4.6 — synthesized from aggregate training data
subcutaneous injection4 mgonce weeklybiohackers and self-experimenters pursuing fat loss after tolerating 2 mg[S] Claude Sonnet 4.6 — synthesized from aggregate training data
subcutaneous injection6 mgonce weeklybiohackers pursuing aggressive fat loss; individuals with obesity or high starting body weight[S] Claude Sonnet 4.6 — synthesized from aggregate training data
subcutaneous injection8 mgonce weeklyexperienced biohackers tolerating lower doses; individuals with significant weight loss goals[S] Claude Sonnet 4.6 — synthesized from aggregate training data
subcutaneous injection12 mgonce weeklyaggressive biohackers; typically heavier individuals or those specifically chasing maximum fat loss outcomes[S] Claude Sonnet 4.6 — synthesized from aggregate training data
subcutaneous injection2 mg → 4 mg → 6 mg → 8 mgonce weekly per stepbiohackers and self-experimenters new to GLP-1/triple agonist class peptides[S] Claude Sonnet 4.6 — synthesized from aggregate training data
subcutaneous injection4 mgonce weeklybiohackers who reached target weight or body composition and are transitioning to maintenance[S] Claude Sonnet 4.6 — synthesized from aggregate training data
subcutaneous injection2 mgonce weeklylean biohackers using Retatrutide for metabolic health or longevity rather than aggressive fat loss[S] Claude Sonnet 4.6 — synthesized from aggregate training data

Tier key: Research = PMID-cited study · [C] = scraped community source · [S] = model-synthesized from aggregate community reports (softer evidence). How we source.

Safety signals

  • Gastrointestinal adverse events (nausea, vomiting, diarrhea, constipation) — most common AEs across trials; dose-related, mostly mild-to-moderate; partially mitigated by lower starting doses and slower escalation PMID 37366315
  • Gastrointestinal adverse events (nausea, diarrhea, vomiting, constipation) reported in 35% of retatrutide-treated participants (vs. 13% placebo) in Phase 2 T2D trial; higher frequency with faster escalation (50% at 8 mg fast escalation vs. 13% placebo) PMID 37385280
  • Dose-dependent increases in heart rate peaking at 24 weeks and declining thereafter in Phase 2 obesity trial PMID 37366315
  • Two deaths in Phase 3 T2D trial (both in the retatrutide 4 mg group), assessed by investigators as unrelated to study drug; discontinuations due to AEs 2–5% with retatrutide vs. 0% with placebo PMID 42250575
  • Higher AE risk with retatrutide compared to dual agonists and GLP-1RAs in Bayesian network meta-analysis (highest AE risk among agents compared) PMID 40685589
  • Serious adverse events occurred in 3–9% of participants across treatment groups in the body composition substudy (Phase 2, T2D); no deaths reported in this substudy PMID 40609566
  • Increased frequency of mild-to-moderate GI adverse events at highest doses, likely due to rapid dose escalation and higher starting dose, noted in review PMID 41785010
  • GLP-1 receptor agonist class signal: slightly increased risk of pancreatitis in meta-analysis of GLP-1 RA RCTs (including retatrutide); pancreatic cancer risk not significantly elevated overall PMID 40988099
  • Positive inotropic effects on isolated human atrial preparations at 10–100 nM; clinical cardiovascular significance of this ex vivo finding is not established in the reviewed abstracts PMID 40613938
  • Described as lacking established human safety profile when used outside clinical supervision; risks of contamination, manufacturing impurities, inaccurate dosing, and supraphysiological hormonal signaling noted for unregulated use PMID 42757290

Contraindications

  • No absolute contraindications are explicitly stated in the reviewed abstracts. Phase 2 T2D trial excluded participants outside the age range 18–75 years or outside HbA1c 7.0–10.5% and BMI 25–50 kg/m²; these represent study eligibility criteria, not formally stated contraindications. PMID 37385280
  • Phase 3 T2D trial enrolled adults ≥18 years with BMI ≥23 kg/m² and HbA1c 7.0–9.5%; populations outside these parameters were not studied in this trial. PMID 42250575
  • GLP-1 receptor agonist class: more severe side effects include pancreatitis, allergic reactions, renal function disorders, and possibly increased risk of thyroid cancer, noted as class concerns for GLP-1 RAs including retatrutide. PMID 40042613

References

  1. [1] PMID 37366315 — Phase 2 RCT (n=338, 48 weeks, subcutaneous once-weekly). Least-squares mean percentage change in body weight at 48 weeks: -8.7% (1 mg), -17.1% (combined 4 mg),
  2. [2] PMID 39761578 — Systematic review: Retatrutide 12 mg once weekly produced weight loss of up to 22.1% (95% CI 19.3%–24.9%) after 48 weeks compared with placebo, exceeding tirzep
  3. [3] PMID 39305981 — Network meta-analysis: retatrutide 12 mg (-22.10% body weight, -17.00 cm waist circumference) and 8 mg (-20.70%, -15.90 cm) were the two most efficacious treatm
  4. [4] PMID 40685589 — Bayesian NMA: retatrutide achieved equivalent mean weight loss to dual agonists (-11.0 kg), surpassing GLP-1RAs (-9.0 kg), and excelled at achieving ≥15% weight
  5. [5] PMID 39817343 — Systematic review and meta-analysis of 4 RCTs: 12 mg dose showed the most significant reductions in body weight, BMI, and waist circumference, and the highest p
  6. [6] PMID 37385280 — Phase 2 RCT (n=281, 36 weeks, USA). In people with T2D, retatrutide reduced HbA1c by up to -2.02% (12 mg) vs. -0.01% placebo at 24 weeks. Bodyweight decreased d
  7. [7] PMID 42250575 — Phase 3 RCT (n=537, 40 weeks, USA/Mexico/India). Retatrutide as monotherapy for T2D inadequately controlled by diet/exercise: mean HbA1c change -1.69% (4 mg), -
  8. [8] PMID 41785010 — Review: HbA1c decreased by up to 2.16% and fasting glucose by up to 69.1 mg/dL in subjects with T2DM. Weight loss up to 16.94% in T2DM subjects. GI adverse even
  9. [9] PMID 38858523 — Phase 2a RCT substudy (n=98, 48 weeks subcutaneous once-weekly). Mean relative change from baseline in liver fat at 24 weeks: -42.9% (1 mg), -57.0% (4 mg), -81.
  10. [10] PMID 40554267 — Review: retatrutide reduced hepatic fat on MRI-PDFF placebo-subtracted by 81% after 48–72 weeks, the largest reduction reported among semaglutide, tirzepatide,
  11. [11] PMID 40489581 — Systematic review and meta-analysis: among GLP-1RAs studied, retatrutide displayed the most obvious treatment effects on liver fat content reduction.
  12. [12] PMID 40609566 — Phase 2 body composition substudy (n=189 enrolled, 103 completed, DXA-measured). Percent reduction in total fat mass: 26.1% (8 mg pooled), 23.2% (12 mg), 15.2%
  13. [13] PMID 42371360 — Systematic review and meta-analysis of RCTs: retatrutide significantly decreased systolic BP (WMD -6.79 mmHg, 95% CI -8.36 to -5.23, p<0.0001), diastolic BP (WM
  14. [14] PMID 40726454 — Post-hoc analysis of two phase 2 RCTs: ANGPTL3/8 reductions observed with 8 mg and 12 mg retatrutide in T2D participants and with 1, 4, 8, and 12 mg in particip
  15. [15] PMID 40916752 — Phase 2 pre-specified exploratory analysis (n=275, T2D). Retatrutide ≥4 mg vs. placebo: greater reductions in overall appetite, hunger, and prospective food con
  16. [16] PMID 41090431 — TRIUMPH Phase 3 program design: OSA protocols nested within TRIUMPH-1 and TRIUMPH-2 weight management basket trials (>5800 total participants). Primary OSA endp
  17. [17] PMID 41160422 — TRANSCEND-CKD Phase 2b mechanistic study (n=146 randomized, eGFR 25–75 mL/min/1.73 m², with/without T2D). Participants randomized 1:1 to once-weekly retatrutide
  18. [18] PMID 39868848 — Preclinical study: retatrutide inhibited the hexosamine biosynthetic pathway (HBP) and YAP O-GlcNAcylation, leading to increased YAP degradation and decreased t
  19. [19] PMID 40613938 — Ex vivo human right atrial preparations (open heart surgery patients): retatrutide (10–100 nM, cumulative) elevated force of contraction in a concentration- and
  20. [20] PMID 40988099 — GLP-1 receptor agonist class signal: slightly increased risk of pancreatitis in meta-analysis of GLP-1 RA RCTs (including retatrutide); pancreatic cancer risk n
  21. [21] PMID 42757290 — Described as lacking established human safety profile when used outside clinical supervision; risks of contamination, manufacturing impurities, inaccurate dosin
  22. [22] PMID 40042613 — GLP-1 receptor agonist class: more severe side effects include pancreatitis, allergic reactions, renal function disorders, and possibly increased risk of thyroi
  23. [23] PMID 37885280 — in-prose reference
  24. [24] PMID 41545327 — in-prose reference
  25. [25] PMID 39724554 — in-prose reference
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