Units to mg converter for tirzepatide vials
For compounded tirzepatide vials, where the concentration changes between pharmacies and fills: enter the concentration from the label and the dose from your prescription to get millilitres and U-100 syringe units, or enter the units on your instructions to check how many milligrams they contain. Brand multi-dose concentrations are listed for reference.
Inputs
Exactly as written on your prescription, in milligrams. Nothing is pre-filled on purpose.
Result
Enter the vial concentration and the prescribed dose in mg.
For reference: brand multi-dose concentrations
Zepbound and Mounjaro multi-dose vials and KwikPens hold four doses in 2.4 mL, so each dose is 0.6 mL. The concentration changes with the strength. This is why a compounded vial's concentration has to be read every time: there is no single tirzepatide concentration.
| Dose | Container | mg/mL | Dose volume |
|---|---|---|---|
| 2.5 mg | 10 mg / 2.4 mL | 4.17 | 0.6 mL (60 units) |
| 5 mg | 20 mg / 2.4 mL | 8.33 | 0.6 mL (60 units) |
| 7.5 mg | 30 mg / 2.4 mL | 12.5 | 0.6 mL (60 units) |
| 10 mg | 40 mg / 2.4 mL | 16.7 | 0.6 mL (60 units) |
| 12.5 mg | 50 mg / 2.4 mL | 20.8 | 0.6 mL (60 units) |
| 15 mg | 60 mg / 2.4 mL | 25 | 0.6 mL (60 units) |
Formulashown in full, nothing hidden
concentration (mg/mL) = total mg in vial / total mL in vial volume (mL) = prescribed dose (mg) / concentration (mg/mL) units (U-100) = volume (mL) x 100 dose (mg) = units / 100 x concentration (mg/mL) doses per vial = total mg in vial / prescribed dose (mg)
Example: a compounded vial labelled 30 mg in 3 mL is 10 mg/mL. A prescribed 5 mg dose is 5 / 10 = 0.5 mL, which is 50 units, and the vial holds six such doses. The same 5 mg from a 17 mg/mL vial is 0.294 mL, about 29 units. Same dose, different volume.
Assumptions, checked September 4, 2026
- Units are U-100 insulin-syringe graduations: 100 units per mL, 1 unit = 0.01 mL. They measure liquid, not tirzepatide. If your syringe is not U-100, ignore the units figure.
- The concentration is used exactly as you typed it. Compounded vials vary between pharmacies and between fills. Read every new label.
- Syringe graduations: 0.3 mL syringes are marked in half units, 0.5 mL in single units, 1 mL in 2-unit steps. Rounding is to the nearest mark.
- Brand single-dose pens and vials contain one dose in 0.5 mL and are not drawn with an insulin syringe; brand KwikPens set the dose mechanically. The brand table above is context only.
- FDA reports dosing errors with compounded GLP-1 drugs where patients drew the wrong number of units or confused units with mg or mL. That page counted more than 730 adverse event reports for compounded tirzepatide as of May 31, 2026.
- Compounded tirzepatide is not FDA approved and is not interchangeable with Zepbound or Mounjaro.
This calculator is an arithmetic aid for medication a licensed prescriber has already prescribed. It does not recommend a dose. Confirm any result with your prescriber or pharmacist before use.
Sources
- Zepbound (tirzepatide) prescribing information, Eli Lilly, DailyMed set id 487cd7e7-434c-4925-99fa-aa80b1cc776b, revised 08/2026
- ISMP Guidelines for Optimizing Safe Subcutaneous Insulin Use in Adults (U-100 syringe graduations)
- FDA: FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss (dosing errors with compounded products), current as of September 1, 2026
- FDA: Human Drug Compounding (compounded drugs are not FDA approved)
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Educational, not medical advice. Read the medical disclaimer.