Tirzepatide Dosage Calculator
Tirzepatide is a once-weekly injection that activates both GIP and GLP-1 receptors. With a compounded multi-dose vial, the units you draw depend on how much water was added — this calculator does that conversion for you.
- Common vials
- 5 mg · 10 mg · 15 mg · 20 mg · 30 mg
- Dosing frequency
- Once weekly
- Half-life
- About 5 days
FDA-approved as Mounjaro® and Zepbound® pens. Compounded vials are not FDA-approved.
Step 1
Your vial & dose
Step 2
Step 3
Syringe size
Smaller barrels have finer marks, which makes small doses easier to read.
Live syringe preview · 100-unit
Draw to
50 units
= 0.5 mL of liquid
- Concentration
- 5 mg/mL
- Each unit contains
- 50 mcg
- Your dose
- 2.5 mg
- Doses per vial
- 4
Show the math
- Concentration = 10 mg ÷ 2 mL = 5 mg/mL
- Volume = 2.5 mg ÷ 5 mg/mL = 0.5 mL
- Units = 0.5 mL × 100 = 50 units
Dosing schedule
Label titration schedule
Based on the FDA labels for Mounjaro® and Zepbound®: start at 2.5 mg weekly, then increase in 2.5 mg steps after at least 4 weeks on each dose, up to 15 mg. Your prescriber may hold or adjust any step.
Weeks 1–4
2.5 mg
Weeks 5–8
5 mg
Weeks 9–12
7.5 mg
Weeks 13–16
10 mg
Weeks 17–20
12.5 mg
Weeks 21+
15 mg
| Weeks | Weekly dose | Volume | Draw to | Note |
|---|---|---|---|---|
| 1–4 | 2.5 mg | 0.5 mL | 50 units | Starting dose← your dose |
| 5–8 | 5 mg | 1 mL | 100 units | |
| 9–12 | 7.5 mg | 1.5 mL | 150 units | 2 draws needed |
| 13–16 | 10 mg | 2 mL | 200 units | 2 draws needed |
| 17–20 | 12.5 mg | 2.5 mL | 250 units | 3 draws needed |
| 21+ | 15 mg | 3 mL | 300 units | 3 draws needed |
How to mix
How to reconstitute a peptide vial in 5 steps
- 01
Clean
Wash your hands. Wipe the rubber tops of the peptide vial and the bacteriostatic water with an alcohol swab and let them air-dry.
- 02
Draw the water
With a new syringe, draw 2 mL of bacteriostatic water — the same number you entered in the calculator. Use several draws if it’s more than your syringe holds.
- 03
Add it slowly
Insert the needle at an angle and let the water run down the inside wall of the vial, not straight onto the powder.
- 04
Swirl, don’t shake
Gently swirl or roll the vial until the powder dissolves completely. The liquid should look clear.
- 05
Label & refrigerate
Write the date and concentration (5 mg/mL) on the vial and keep it in the fridge.
Storing a mixed vial
- Keep it refrigerated at 2–8 °C (36–46 °F). Don’t freeze it.
- Protect it from light and heat.
- Follow the beyond-use date on your pharmacy label. If the liquid turns cloudy or has particles, don’t use it.
Please read before injecting
Always confirm your dose, concentration and syringe markings with your prescriber or pharmacist. Small calculation errors can have serious consequences. This tool does math — it doesn’t tell you what dose to take.
Sources
References
- FDA prescribing information — tirzepatide (DailyMed)
- SURMOUNT-1 trial, N Engl J Med 2022
- SURPASS-2 trial, N Engl J Med 2021
Last updated October 2026. Example vial: 10 mg + 2 mL = 5 mg/mL.
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