Tirzepatide dosage and protocol
Last reviewed Oct 7, 2026. Editorial policy
US regulatory status: FDA-approved drug
Tirzepatide is a dual GIP/GLP-1 receptor agonist that outperforms semaglutide in clinical trials for weight loss, showing up to 22% body weight reduction. Marketed as Mounjaro (diabetes) and Zepbound (obesity). Acts on two incretin pathways simultaneously, producing superior appetite suppression and metabolic improvements compared to GLP-1 mono-agonists.
- Vial size: 15 mg
- Reconstitution: 2 mL bacteriostatic water
- Concentration: 7.5 mg/mL
- Administration: subcutaneous
Research areas
- Fat Loss
- Weight Management
- Glucose Regulation
- Metabolic Health
- Appetite Suppression
Quick start
- Reconstitute: Add 2.0 mL bacteriostatic water → 7.5 mg/mL concentration
- Typical weekly range: 2.5–15 mg once weekly (gradual 4-week titration steps)
- Easy measuring: At 7.5 mg/mL, 1 unit = 0.01 mL = 75 mcg on a U-100 syringe
- Storage: Lyophilized at −20°C; after reconstitution, refrigerate at 2–8°C and use within 28 days
Dosing protocol
| Phase | Dose | Frequency | Volume |
|---|---|---|---|
| Weeks 1–4 | 2.5 mg | Once weekly (SC) | 0.33 mL (33 units) |
| Weeks 5–8 | 5 mg | Once weekly (SC) | 0.67 mL (67 units) |
| Weeks 9–12 | 7.5 mg | Once weekly (SC) | 1.0 mL (100 units) |
| Weeks 13–16 | 10 mg | Once weekly (SC) × 2 injections | 0.67 mL × 2 (67 units each) |
How it works
Tirzepatide is a single 39-amino-acid peptide that activates two incretin receptors: the glucose-dependent insulinotropic polypeptide (GIP) receptor and the glucagon-like peptide-1 (GLP-1) receptor. A fatty acid side chain lets it bind albumin, giving a half-life of about five days and allowing once-weekly dosing. Receptor activation increases glucose-dependent insulin secretion, lowers glucagon, slows gastric emptying, and acts on brain appetite centres to reduce food intake. It is FDA-approved as Mounjaro (2022) for type 2 diabetes alongside diet and exercise, and as Zepbound (2023) for chronic weight management in adults with obesity or overweight with a weight-related condition; Zepbound was later also approved for moderate to severe obstructive sleep apnea in adults with obesity. Approved dosing starts at 2.5 mg weekly and rises in 2.5 mg steps every four weeks to maintenance doses of 5, 10 or 15 mg. In the phase 3 trial programmes, tirzepatide lowered HbA1c and body weight more than placebo and several active comparators, and at the highest dose average weight loss in obesity trials exceeded 20% over about 72 weeks. A head-to-head trial showed greater weight loss than semaglutide. Weight tends to be regained after stopping.
Units chart for a 15 mg vial
| Water added | Strength | 1 unit = | 2.5 mcg | 5 mcg | 7.5 mcg | 10 mcg |
|---|---|---|---|---|---|---|
| 1 mL | 15 mg/mL | 150 mcg | 0 units | 0 units | 0.1 units | 0.1 units |
| 2 mL | 7.5 mg/mL | 75 mcg | 0 units | 0.1 units | 0.1 units | 0.1 units |
| 3 mL | 5 mg/mL | 50 mcg | 0.1 units | 0.1 units | 0.2 units | 0.2 units |
Units on a U-100 insulin syringe (100 units = 1 mL).
Pages for each vial size and water volume
Reconstitution steps
- Draw 2.0mL bacteriostatic water with a sterile syringe
- Inject slowly down the vial wall; avoid foaming
- Gently swirl/roll until dissolved (do not shake)
- Label with reconstitution date and refrigerate at 2–8°C (35.6–46.4°F), protected from light; use within 28 days
Storage
Evidence: FDA label. From the US prescribing information of the approved product. It applies to that product only.
Applies to: Mounjaro and Zepbound KwikPen (label). Single-dose pens and vials may be kept unrefrigerated up to 30 °C for a total of 21 days.
- Powder or unopened: Not a powder: ready-made pens and vials. Unused: refrigerator, 2–8 °C (36–46 °F). Do not freeze.
- Mixed or in use: After first use a KwikPen may be kept at room temperature up to 30 °C (86 °F). Throw it away after 4 doses even if medicine is left.
- Use within: 30 days after mixing or first use
- Light: Keep it in the carton, away from heat and light.
Compounded or "research" tirzepatide vials are not covered by the label. Ask the pharmacy for its beyond-use date.
Sources: Mounjaro prescribing information and Instructions for Use (DailyMed); Zepbound prescribing information and Instructions for Use (DailyMed)
Store lyophilized at -20°C. After reconstitution, refrigerate at 2-8°C and use within 28 days.
Important notes
- Research use only
- Dual GIP + GLP-1 agonist — superior fat loss to semaglutide
- Clinical trials: ~22% body weight reduction
- Mounjaro/Zepbound pharmaceutical equivalent
- Gradual dose escalation required to minimize side effects
Supplies
- Bacteriostatic water
- Insulin syringes (U-100)
- Alcohol swabs