Retatrutide Dosing
Retatrutide should be initiated at 2 mg subcutaneously once weekly, then escalated monthly to 4 mg, 8 mg, and ultimately 12 mg as the maintenance dose, with dose titration guided by tolerability and gastrointestinal side effects.
Dosing Regimen
The evidence from phase 2 and phase 3 trials establishes a clear dose-escalation protocol for retatrutide 1, 2, 3:
- Starting dose: 2 mg subcutaneously once weekly
- Escalation schedule: Increase monthly by increments
- Week 0-4: 2 mg weekly
- Week 5-8: 4 mg weekly
- Week 9-12: 8 mg weekly
- Week 13+: 12 mg weekly (maintenance dose)
The 2 mg starting dose is critical - phase 2 data demonstrated that initiating at 4 mg versus 2 mg resulted in significantly more gastrointestinal adverse events 3. The lower starting dose partially mitigates the dose-related nausea, vomiting, diarrhea, and constipation that are otherwise common with rapid escalation.
Therapeutic Dose Range
All three maintenance doses (4 mg, 8 mg, and 12 mg) demonstrated efficacy, but with dose-dependent responses 1, 2, 3:
- 4 mg: Produces 11.5-17.1% weight reduction and 1.69% HbA1c reduction
- 8 mg: Produces 22.8% weight reduction (obesity trials)
- 12 mg: Produces 24.2% weight reduction and 1.94% HbA1c reduction - this is the optimal dose for maximal efficacy
In type 2 diabetes with obesity, the 12 mg dose achieved 18.8% weight reduction and substantial glycemic improvements 2.
Dose Adjustment Considerations
For gastrointestinal intolerance: Slow the titration schedule or maintain at a lower dose temporarily. The phase 2 trial showed that 92% of participants on 4 mg, 100% on 8 mg, and 100% on 12 mg achieved ≥5% weight loss 3, indicating that submaximal doses can still provide meaningful benefit if the highest dose is not tolerated.
Missed doses: While not explicitly addressed in retatrutide trials, extrapolating from GLP-1 RA guidelines 4:
- If 1-2 doses missed and previously well-tolerated: Resume at same dose
- If 3+ consecutive doses missed: Consider restarting titration schedule
Critical Safety Monitoring
Gastrointestinal effects are the primary concern - diarrhea occurred in 27-34% with retatrutide versus 13% with placebo, and nausea in 14-28% versus 8% 2. These are predominantly mild-to-moderate and diminish over time.
Heart rate increases were observed, peaking at 24 weeks then declining 3. Monitor cardiovascular parameters, particularly in patients with pre-existing cardiac conditions.
Hypotension and dysesthesia occurred more frequently at higher doses (5-6% and 4-7% respectively at 8-12 mg) 2.
Discontinuation rates due to adverse events were 4% at 4 mg, 12% at 9 mg, and 8% at 12 mg 2, indicating the 12 mg dose has acceptable tolerability when properly titrated from 2 mg.