Starting Dose of Zepbound (Tirzepatide)
The FDA-approved starting dose of Zepbound (tirzepatide) is 2.5 mg subcutaneously once weekly for the first 4 weeks. 1
Standard Titration Protocol
After the initial 4-week period at 2.5 mg, the dose should be increased systematically:
- Weeks 1-4: 2.5 mg once weekly (starting dose for tolerability assessment, not therapeutic efficacy) 1, 2
- Week 5 onward: Increase to 5 mg once weekly (first maintenance dose) 1, 2
- After ≥4 weeks at 5 mg: May escalate to 10 mg once weekly if additional weight loss or glycemic control is needed 1, 2
- After ≥4 weeks at 10 mg: May escalate to the maximum approved dose of 15 mg once weekly 1, 2
The 2.5 mg starting dose is specifically designed to minimize gastrointestinal side effects (nausea, vomiting, diarrhea) during the initial adaptation period. 1, 3
Critical Implementation Points
- Injection timing: Administer on the same day each week, at any time of day, with or without meals 1
- Injection sites: Rotate between abdomen, thigh, or upper arm 1
- Dose-spacing flexibility: The weekly injection day may be shifted if at least 48 hours (2 days) separate consecutive doses 1
Why the 2.5 mg Starting Dose Matters
The initial 2.5 mg dose is not a therapeutic dose for weight loss—it serves as a tolerability-building phase. 2 Gastrointestinal adverse events (nausea 17-31%, diarrhea 12-23%, vomiting 6-12%) are dose-dependent and occur most frequently during dose escalation. 3 Starting at 2.5 mg and increasing every 4 weeks allows the body to adapt, reducing discontinuation rates due to side effects. 3
Monitoring During Initial Titration
- Week 4 (before first dose increase): Assess gastrointestinal tolerance and confirm patient can proceed to 5 mg 1, 3
- Monthly during dose escalation: Evaluate weight loss progress, blood pressure, and adverse effects 1
- Weeks 12-16 on therapeutic dose: Formal efficacy assessment—expect ≥5% body weight loss to justify continuation 1, 2
Common Pitfall to Avoid
Do not skip the 2.5 mg starting dose and begin directly at 5 mg or higher. 1 Initiating at the maintenance dose markedly increases gastrointestinal adverse events and treatment discontinuation rates. 1 The slow titration protocol (4-week intervals) is essential for tolerability and long-term adherence. 3
Contraindications Before Starting
Screen for absolute contraindications before prescribing the first 2.5 mg dose: