Tirzepatide vs Retatrutide: Mechanism, Studies and Dose Differences
Technical comparison between the FDA-approved GLP-1/GIP dual agonist and the Phase III triple agonist setting new weight-loss records.
What is Tirzepatide
Tirzepatide is a synthetic dual-agonist activating GLP-1 and GIP receptors. FDA-approved in 2022 as Mounjaro (T2D) and Zepbound (obesity). Studied in SURMOUNT and SURPASS.
Mechanism: mimics gut incretins released after a meal — glucose-dependent insulin, slowed gastric emptying, reduced appetite. GIP adds adipose tissue effects pure GLP-1 lacks.
What is Retatrutide
Retatrutide is a triple-agonist: GLP-1, GIP and glucagon. Phase III (Eli Lilly). NEJM 2023 / TRIUMPH-1: up to 24.2% weight loss at 48 weeks with 12 mg — superior to any published Tirzepatide result.
Mechanism: why triple beats dual
Glucagon counterintuitively raises hepatic glucose, but at sub-hyperglycemic doses increases thermogenesis and lipolysis. Simultaneous GLP-1 offsets the glycemic effect.
Dose comparison
| Variable | Tirzepatide | Retatrutide |
|---|---|---|
| Receptors | GLP-1 + GIP | GLP-1 + GIP + Glucagon |
| Status | FDA approved | Phase III |
| Dose range | 2.5–15 mg/wk | 1–12 mg/wk |
| Weight loss (52 wk) | ~20.9% | ~24.2% |
| Half-life | ~5 days | ~6 days |
How to choose
For regulated evidence + safety: Tirzepatide.
For maximum fat-loss ceiling: Retatrutide.
Reconstitution
Both lyophilized. Reconstitute with BAC water. Example: 10 mg vial + 2 mL = 5 mg/mL. Calculator.
Stacks
- 5-Amino-1MQ
- SLU-PP-332
- AOD-9604
- MOTS-c
⚠ Research use only. Not medical advice.