📈 Tirzepatide Dosage Calculator
Select your titration phase, vial size, and bacteriostatic water volume — concentration, draw volume, and syringe units computed instantly for every weekly injection.
Tirzepatide Reconstitution & Dose Calculator
Tirzepatide (Mounjaro / Zepbound) is a dual GIP/GLP-1 receptor agonist developed by Eli Lilly. Unlike semaglutide's single GLP-1 pathway, tirzepatide's additional GIP activity enhances insulin secretion, reduces glucagon, and appears to produce greater average weight loss in head-to-head comparisons. Like all injectable peptides supplied as lyophilised powder, it must be reconstituted with bacteriostatic water before subcutaneous injection. The six-phase titration schedule escalates from 2.5 mg to 15 mg per week over 20+ weeks to manage tolerability.
Select your current phase, enter your vial size and BAC water volume, choose your syringe — and the calculator returns the exact concentration, mL volume, and U-100 unit mark for your weekly dose.
You have a 10 mg tirzepatide vial, add 1 mL BAC water, and want the Phase 1 dose of 2.5 mg (2,500 mcg) on a 0.5 mL syringe.
- Concentration = (10 × 1,000) ÷ 1 = 10,000 mcg/mL
- Volume = 2,500 ÷ 10,000 = 0.25 mL
- U-100 draw = 0.25 × 100 = pull to the 25-unit mark
- Doses per vial = floor(10,000 ÷ 2,500) = 4 doses
Select your current titration phase
Tirzepatide vial size
Bacteriostatic water added
What syringe volume are you using?
Select your phase and inputs above to generate your draw guide.
Based on SURMOUNT trial protocol — once-weekly SC injection. Reference draw assumes 10 mg vial + 1 mL BAC water = 10,000 mcg/mL. Escalation may be held at any phase.
| Phase | Weeks | Dose | Injections | 10 mg Vials | 15 mg Vials | Draw (10mg / 1mL BAC) |
|---|---|---|---|---|---|---|
| Phase 1 | 1–4 | 2.5 mg (2,500 mcg) | 4 | 1 | 1 | 25 units U-100 |
| Phase 2 | 5–8 | 5 mg (5,000 mcg) | 4 | 2 | 2 | 50 units U-100 |
| Phase 3 | 9–12 | 7.5 mg (7,500 mcg) | 4 | 3 | 2 | 75 units U-100 |
| Phase 4 | 13–16 | 10 mg (10,000 mcg) | 4 | 4 | 3 | 100 units U-100 |
| Phase 5 | 17–20 | 12.5 mg (12,500 mcg) | 4 | 5 | 4 | 125 units* (split dose) |
| Phase 6 | 21+ | 15 mg (15,000 mcg) | ongoing | 6+ | 4+ | 150 units* (split dose) |
* Phases 5–6 at 10,000 mcg/mL exceed 1.0 mL syringe capacity. Use 15 mg vial + 1 mL BAC (15,000 mcg/mL) for 83 and 100-unit draws respectively, or split across two injection sites.
Tirzepatide Calculator — Frequently Asked Questions
How does tirzepatide differ from semaglutide (Ozempic)?
Tirzepatide is a dual GIP/GLP-1 receptor agonist — it activates both glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptors. Semaglutide targets only GLP-1 receptors. The additional GIP activity in tirzepatide enhances insulin secretion in a glucose-dependent manner, reduces glucagon, and may improve fat oxidation. SURMOUNT-1 trial data showed average weight loss of ~22% at 15 mg vs ~15–17% for semaglutide 2.4 mg (Wegovy) at 68 weeks. Tirzepatide also has a shorter half-life (~5 days vs ~7 days for semaglutide), which affects how quickly side effects resolve if dosing is paused.
Why does the titration use six phases instead of four like semaglutide?
Tirzepatide reaches much higher absolute doses (up to 15 mg/week vs 2 mg/week for Ozempic). Compressing this range into four phases would create larger dose jumps per step, increasing GI side effect severity. The six-phase protocol makes each escalation step proportionally smaller, allowing better tolerability at higher doses. Some protocols extend each phase to 8 weeks instead of 4 for users who experience persistent nausea.
What vial size is best for higher tirzepatide doses?
A 15 mg vial reconstituted with 1 mL BAC water gives 15,000 mcg/mL — producing draws of 50, 67, 83, and 100 units for the 7.5, 10, 12.5, and 15 mg phases respectively. This keeps all doses within a single 1.0 mL syringe. A 10 mg vial + 1 mL BAC is ideal for Phases 1–4 but requires split injections at Phases 5–6 (12.5–15 mg exceed 10,000 mcg capacity). Use the calculator above to optimise your reconstitution volume for the phase you're currently in.
How long does a reconstituted tirzepatide vial last?
Once reconstituted with bacteriostatic water and stored refrigerated at 2–8°C, the solution is stable for 28 days. At Phase 1 (one 2.5 mg dose per week from a 10 mg vial), you have 4 doses that comfortably fit within 28 days. At Phase 2 (5 mg), you get 2 doses per vial — one vial per 2 weeks. Label every vial with the reconstitution date on the day you mix it.
Can tirzepatide and semaglutide be used together?
No. Combining two GLP-1 receptor agonists significantly amplifies GI side effects (nausea, vomiting, gastroparesis) and creates additive cardiovascular risk without established additional benefit. Both compounds target overlapping receptor pathways. Clinical guidelines and research protocols do not support concurrent use. If transitioning between compounds, a washout period appropriate to each drug's half-life is recommended before starting the other.