Tirzepatide Dosage Calculator (mg to Units & mL)
Convert a tirzepatide dose in mg to mL and U-100 insulin syringe units for a compounded vial, from the vial mg/mL or the powder and water you mix, with the 2.5 mg to 15 mg titration table and a syringe-size check.
How it works
concentration (mg/mL) = mg in vial ÷ mL of liquid · volume (mL) = dose (mg) ÷ concentration · U-100 syringe units = mL × 100 · doses per vial = mg in vial ÷ dose
Branded tirzepatide (Mounjaro, Zepbound) comes in single-dose pens or vials, but compounded tirzepatide is usually a multi-dose vial drawn up with an insulin syringe. The calculation is the same for any drug: millilitres = milligrams ÷ concentration, and on a U-100 syringe 1 mL = 100 units. The label titration starts at 2.5 mg once weekly for 4 weeks and rises by 2.5 mg every 4 weeks as tolerated, to a maximum of 15 mg. Higher concentrations mean fewer units for the same dose, so a mix-up between vials is dangerous.
Worked example
A vial labelled 10 mg/mL holding 2 mL (20 mg) and the 2.5 mg starting dose: 2.5 ÷ 10 = 0.250 mL, which is 25.0 units (0.250 mL) on a U-100 syringe. Each unit holds 100.0 mcg and the vial holds 8 weekly doses. The 15 mg maximum would need 1.500 mL = 150 units — more than a 1 mL syringe, so it would take two draws or a stronger vial.
Sources: Zepbound (tirzepatide) prescribing information — Eli Lilly · Mounjaro (tirzepatide) prescribing information — Eli Lilly · FDA: concerns with unapproved GLP-1 drugs used for weight loss
Frequently asked questions
How many units is 2.5 mg of tirzepatide?
At 10 mg/mL, 2.5 mg is 0.25 mL = 25 units on a U-100 syringe. At 20 mg/mL it is 12.5 units, at 5 mg/mL 50 units. Always use the concentration printed on your vial.
What is the tirzepatide dose schedule?
Per the Mounjaro and Zepbound labels: 2.5 mg once weekly for 4 weeks (a starter dose), then 5 mg, increasing by 2.5 mg no sooner than every 4 weeks as needed and tolerated, to 7.5, 10, 12.5 and a maximum of 15 mg weekly.
How long does a tirzepatide vial last?
Divide the total mg in the vial by your weekly dose. A 20 mg vial lasts 8 weeks at 2.5 mg, 4 weeks at 5 mg and 2 weeks at 10 mg. Also respect the beyond-use date on the pharmacy label, whichever comes first.
Can I use a 0.3 mL syringe?
Only if the dose fits: a 0.3 mL syringe holds 30 units. Larger doses need a 0.5 mL (50 units) or 1 mL (100 units) syringe. Smaller syringes have finer markings and are more accurate for small volumes.
Related calculators
Educational calculation only, not medical advice. Follow your prescription, the product label and your pharmacist: confusing milligrams, millilitres and syringe units is a common cause of injection overdoses. Use only medicines from a licensed pharmacy.