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Tirzepatide vs Retatrutide

Dual GLP-1/GIP agonist vs triple GLP-1/GIP/Glucagon agonist — what the Phase 2 data shows

Tirzepatide
Mounjaro / Zepbound
VS
Retatrutide
LY3437943 (Phase 3)
FactorTirzepatideRetatrutide
Mechanism Dual GLP-1 + GIP agonist Triple GLP-1 + GIP + Glucagon agonist
Avg Weight Loss 20.9% (SURMOUNT Phase 3) 24.2% (Phase 2, NEJM 2023)
Highest dose studied (phase 2) 15 mg/week 12 mg/week
Starting Dose 2.5 mg/week No approved dose (investigational)
FDA Approval ✅ Approved (Mounjaro/Zepbound) ❌ Phase 3 trials ongoing (2025)
Liver Fat Reduction Strong Strongest studied (NASH potential)
Heart Rate Effect Mild increase More pronounced increase (glucagon)
GI Tolerance Good at standard titration Similar, titrate slowly for glucagon effects
Compounded Available Yes — widely available Yes — but less validated than Phase 3 data
Long-term Data Phase 3 complete, 2+ years data Phase 2 only — Phase 3 ongoing
Winner Proven, approved, widely available Greater weight loss potential when approved

⚖️ The Verdict

Retatrutide's Phase 2 data is extraordinary — 24.2% average weight loss approaches bariatric surgery outcomes. The addition of glucagon receptor agonism adds meaningful thermogenic (calorie-burning) effects that tirzepatide lacks. However, Phase 2 data is not Phase 3 data. Tirzepatide has completed Phase 3 trials, is FDA-approved, and has robust real-world evidence. For most people in 2025-2026, tirzepatide remains the gold-standard approved option. Retatrutide is the most promising pipeline compound.

⚠️ Research purposes only. Not medical advice. Consult a licensed healthcare provider.
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