Drawing tirzepatide from a vial (tirz, in the shorthand people use) with an insulin syringe, the units you draw depend on your vial’s concentration (mg per mL) — the same milligrams read as a different unit count at different strengths. Here are the standard dose steps at common concentrations, plus how to run the numbers for your vial. It is mixing-math, not a dose recommendation; confirm your dose with your prescriber and read the mg/mL on your own label.
On a U-100 insulin syringe, 100 units = 1 mL. Concentration (mg/mL) = vial mg × 1000 ÷ water mL, in mg per mL. Units = (dose mg ÷ concentration mg/mL) × 100. And 1 mg = 1000 mcg.
Illustrative only — use the concentration on YOUR label. Not a recommendation to take any dose.
| Dose | 10 mg/mL | 20 mg/mL |
|---|---|---|
| 2.5 mg | 25 units | 12.5 units |
| 5 mg | 50 units | 25 units |
| 7.5 mg | 75 units | 37.5 units |
| 10 mg | 100 units | 50 units |
| 12.5 mg | 125 units* | 62.5 units |
| 15 mg | 150 units* | 75 units |
*Over 100 units is more than a standard 1 mL insulin syringe holds — a more concentrated vial keeps the draw on one syringe.
A vial labeled 20 mg/mL, dose 5 mg: 5 ÷ 20 = 0.25 mL, and 0.25 mL × 100 = 25 units. Halve the concentration and the same 5 mg becomes 50 units — the reason you always read your own label.
Choosing a concentration that yields a whole-number draw is easier to measure and keeps you clear of a 10×/100× error (usually an mg/mcg slip) or a U-40-vs-U-100 mix-up. If a number looks off by a factor of ten, recheck the concentration first. Run any vial and dose through the free calculator.
Because they are different concentrations. Units come from volume, and volume = dose ÷ concentration — so a more concentrated vial needs fewer units for the same milligrams.
Look for the mg per mL on the label, or compute it: vial mg × 1000 ÷ water mL, in mg per mL. Compounded vials vary, so never assume.
Brand pens are pre-dosed (no units). Compounded vials come in different concentrations, so use the mg/mL on your own vial.
Read the nearest mark carefully, or pick a water volume that makes the draw a round number; the calculator can solve for that.
No — it is mixing-math only. The dose is set by your prescriber; this just converts a milligram amount to a syringe mark.