Two weekly incretin compounds at very different stages of evidence.
These are not at the same stage of evidence. Tirzepatide is approved with published phase 3 results and a label-defined escalation. Retatrutide is still in phase 3 and approved nowhere — every figure circulating for it traces back to a phase 2 dose-ranging trial.
| Retatrutide | Tirzepatide | |
|---|---|---|
| What it is | LY3437943, triple GIP/GLP-1/glucagon agonist | Dual GIP/GLP-1 receptor agonist |
| Evidence tier | Clinical | Clinical |
| Route | Subcutaneous | Subcutaneous |
| Half-life | ~6 days | ~5 days |
| Vial sizes | 10/15/30 mg | 20/30 mg |
| Water we suggest | 1 mL, 1.5 mL, 3 mL | 1.5 mL, 2 mL |
| Reported doses | 1 mg, 4 mg, 6 mg, 8 mg | 2.5 mg, 5 mg, 7.5 mg, 10 mg |
| Has a schedule | Weekly 1 mg step-up — most settle at 4–6 mg | Approved-label escalation |
Tirzepatide is a dual GIP/GLP-1 agonist. Retatrutide adds glucagon-receptor agonism, which raises energy expenditure and drives hepatic fat mobilisation rather than adding more of the same effect. Its tolerability profile is less well characterised simply because less has been published.
Tirzepatide has a defined schedule from the trials and the label. Retatrutide has no equivalent — its 1/4/8/12 mg figures are trial arms, not a ramp. In practice most people settle at 4–6 mg and stop there.