Retatrutide vs Tirzepatide

Triple agonist vs dual agonist

Tirzepatide activates GIP and GLP-1 receptors. Retatrutide adds a third target, the glucagon receptor, which raises energy expenditure on top of the appetite suppression both compounds share. That third arm is the main reason retatrutide's trial weight-loss curve has not plateaued at the same point tirzepatide's does.

Weight-loss data side by side

In SURMOUNT-1, tirzepatide 15 mg produced roughly 20.9% mean body-weight reduction at 72 weeks. Retatrutide's Phase 2 trial reported about 24.2% at 48 weeks on the 12 mg arm, still trending downward at the end of the study. Cross-trial comparisons are indicative, not definitive, because populations and durations differ.

Dosing and titration differences

Both are once-weekly subcutaneous injections with four-week titration steps. Tirzepatide steps 2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg. Retatrutide research protocols typically step 2 → 4 → 8 → 12 mg. Slower steps reduce nausea in both cases.

Side effects and availability

Nausea, constipation and early satiety dominate both profiles and fade after the first weeks at each step. Retatrutide adds a modest heart-rate increase from glucagon-receptor activity. Tirzepatide is FDA-approved as Mounjaro and Zepbound; retatrutide remains investigational and is research-use only.

Frequently asked questions

Is retatrutide stronger than tirzepatide?

Trial data suggests greater mean weight loss for retatrutide, roughly 24% at 48 weeks versus about 21% for tirzepatide at 72 weeks, but the studies are not head-to-head.

Can you switch from tirzepatide to retatrutide?

Research protocols generally restart titration at a low retatrutide dose rather than matching the previous tirzepatide dose, because the glucagon arm changes tolerability.

Is retatrutide approved?

No. Retatrutide is still in clinical development and is not FDA-approved for any indication.