Tirzepatide Dosage Calculator
Tirzepatide is a once-weekly GIP / GLP-1 injection. For a ready-mixed vial, enter the pharmacy label’s concentration and your prescribed dose to calculate U-100 syringe units. Do not add water to a ready-mixed solution.
- Example vial inputs
- 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® injectable solutions, including pens and vials. Compounded vials are not FDA-approved.
Using a branded Zepbound® or Mounjaro® vial, pen or KwikPen? How to tell them apart and read the labelStep 1
Your vial & dose
What’s in your vial?
Vial values are examples. Replace them with your product or pharmacy label values.
Copy the concentration (mg/mL) from your pharmacy label. Don’t add water to a vial that is already liquid.
Step 2
Doses on the FDA label
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 = 5 mg/mL (from your label)
- Volume = 2.5 mg ÷ 5 mg/mL = 0.5 mL
- Units = mL × 100 = 50 units
Dosing schedule
Zepbound® label steps — adult weight management
This is not a calendar to reach 15 mg. For weight management, the prescriber selects 5, 10 or 15 mg weekly for maintenance based on response and tolerability; 2.5 mg is for initiation only. Each later increase requires at least 4 weeks at the previous dose. Zepbound for obstructive sleep apnea has maintenance doses of 10 or 15 mg. Mounjaro for adult type 2 diabetes has a separate label: start at 2.5 mg, then increase by 2.5 mg only if more glycemic control is needed, after at least 4 weeks at the current dose (maximum 15 mg). These brand labels do not prescribe a compounded product’s dose.
First 4 weeks
2.5 mg
Starting dose
After 4 weeks at 2.5 mg
5 mg
Maintenance option
≥ 4 weeks at 5 mg, if needed
7.5 mg
Conditional increase
≥ 4 weeks at 7.5 mg, if needed
10 mg
Maintenance option
≥ 4 weeks at 10 mg, if needed
12.5 mg
Conditional increase
≥ 4 weeks at 12.5 mg, if needed
15 mg
Maintenance option / maximum
Dashed = conditional step. Your prescriber selects the dose for your indication, response and tolerability.
Arithmetic at your entered concentration: 5 mg/mL, 100-unit syringe. Follow the prescribed product’s device instructions; this is not a pen conversion.
| When | Weekly dose | Volume | Draw to | Note |
|---|---|---|---|---|
| First 4 weeks | 2.5 mg | 0.5 mL | 50 units | Starting dose← your dose |
| After 4 weeks at 2.5 mg | 5 mg | 1 mL | 100 units | Maintenance option |
| ≥ 4 weeks at 5 mg, if needed | 7.5 mg | 1.5 mL | 150 units | Conditional increase Exceeds syringe capacity — confirm with pharmacist |
| ≥ 4 weeks at 7.5 mg, if needed | 10 mg | 2 mL | 200 units | Maintenance option Exceeds syringe capacity — confirm with pharmacist |
| ≥ 4 weeks at 10 mg, if needed | 12.5 mg | 2.5 mL | 250 units | Conditional increase Exceeds entered vial amount Exceeds syringe capacity — confirm with pharmacist |
| ≥ 4 weeks at 12.5 mg, if needed | 15 mg | 3 mL | 300 units | Maintenance option / maximum Exceeds entered vial amount Exceeds syringe capacity — confirm with pharmacist |
Before reconstitution
Five checks for a powder vial
For powder (freeze-dried) vials only. If your vial arrived as a liquid, it is already mixed — never add water to it; use the concentration on the label. Approved injectable brands are supplied as solutions. This guide applies only if a pharmacy has specifically supplied powder with preparation instructions; it does not apply to pens or ready-mixed vials.
- 01
Check the product
Confirm that you have a powder intended for preparation and the instructions for that exact product. Ask your pharmacist if anything is unclear.
- 02
Confirm the diluent
Use only the diluent and volume specified in those instructions. The calculator cannot determine whether a diluent or mixing volume is suitable.
- 03
Follow the instructions
Follow the product’s preparation method and the technique your pharmacist taught you. These checks are not a substitute for its Instructions for Use.
- 04
Verify concentration
Use the labeled concentration after preparation, or the total drug amount and final solution volume. The final volume may differ from the amount of diluent added.
- 05
Check storage & discard
Follow the product’s storage conditions and discard time. Some preparations require immediate use. Do not infer a storage period from the calculator.
Storing your vial
- For an approved brand, follow the storage and discard instructions for your exact presentation; pen, single-dose vial and multi-dose vial instructions can differ.
- For compounded GLP-1 vials, follow the pharmacy’s temperature instructions and any earlier discard date. FDA recommends discarding multi-dose compounded GLP-1 vials within 28 days of first use, even if the compounder gives a longer period.
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
- Zepbound prescribing information — dose selection (§2)
- Mounjaro prescribing information — glycemic control (§2.1)
- FDA — unapproved GLP-1 drugs, dosing errors and storage
- SURMOUNT-1 trial, N Engl J Med 2022
- SURPASS-2 trial, N Engl J Med 2021
Last updated October 2026.
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