Tirzepatide Dosage Calculator: mg to Units
Compounded tirzepatide comes in multi-dose vials at concentrations that vary by pharmacy, so the same 5 mg dose can be 25 units from one vial and 50 from another. Enter your vial's mg/mL and your prescribed dose to see exactly what to draw, plus every step of the standard schedule converted for your vial.
Used only to count doses per vial.
= 0.25 mL of a 10 mg/mL solution, delivering 2.5 mg.
Tirzepatide dose steps at 10 mg/mL
Every dose your prescriber may move you through, converted for your vial. Follow your own prescription.
| Dose | mL | Units (U-100) | Typical use |
|---|---|---|---|
| 2.5 mg | 0.25 | 25 | Weeks 1–4 (starting dose) |
| 5 mg | 0.5 | 50 | Weeks 5–8 (first maintenance option) |
| 7.5 mg | 0.75 | 75 | +2.5 mg after ≥4 weeks |
| 10 mg | 1 | 100 | Maintenance option |
| 12.5 mg | 1.25 | 125 | +2.5 mg after ≥4 weeks |
| 15 mg | 1.5 | 150 | Maximum labeled dose |
Tirzepatide mg-to-units chart
Units for each labeled dose at three common compounded concentrations, on a U-100 insulin syringe. Your vial may use a different strength; the calculator handles any value.
| Dose | 8 mg/mL | 10 mg/mL | 20 mg/mL |
|---|---|---|---|
| 2.5 mg | 31.3 units | 25 units | 12.5 units |
| 5 mg | 62.5 units | 50 units | 25 units |
| 7.5 mg | 93.8 units | 75 units | 37.5 units |
| 10 mg | 125 units | 100 units | 50 units |
| 12.5 mg | 156.3 units | 125 units | 62.5 units |
| 15 mg | 187.5 units | 150 units | 75 units |
Anything over 100 units won't fit in a 1 mL syringe. Higher doses are usually dispensed at a higher concentration for exactly this reason.
How the math works
mL = dose (mg) ÷ concentration (mg/mL), and units = mL × 100. So 7.5 mg from a 10 mg/mL vial is 0.75 mL, which is 75 units. If your vial is a powder you mix yourself, the concentration is the mg in the vial divided by the mL of bacteriostatic water you add. Switch the calculator to “Powder” mode to handle that.
The calculation itself is simple. Most errors happen when a vial's concentration changes between refills and the unit count isn't updated, or when a dose written in mg is read as units. The FDA has documented overdoses from exactly this mix-up with compounded GLP-1 vials. Re-check your units every time a new vial arrives.
When dose increases happen
On the labeled schedule, each step lasts at least four weeks. That means a single multi-dose vial often spans a dose change. When it does, the vial's concentration stays the same but your unit count goes up. The schedule table under the calculator shows every step for your vial, so you can see the next number before you need it.
Tirzepatide is injected once a week, on the same day each week. Under the Zepbound label, a missed dose can be taken within 4 days (96 hours); after that, skip it and resume on your usual day.
Frequently Asked Questions
How many units is 2.5 mg of tirzepatide?
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It depends on your vial's concentration. At 10 mg/mL, 2.5 mg is 0.25 mL, or 25 units on a U-100 insulin syringe. At 20 mg/mL it is 12.5 units, and at 8 mg/mL it is about 31 units. Check the mg/mL on your vial label and enter it in the calculator.
How many units is 5 mg of tirzepatide?
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At 10 mg/mL, 5 mg is 0.5 mL or 50 units. At 20 mg/mL, it is 25 units. Doubling the concentration halves the units for the same dose.
What is the standard tirzepatide dose schedule?
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The FDA label for Zepbound and Mounjaro starts at 2.5 mg once weekly for 4 weeks, then increases in 2.5 mg steps at least 4 weeks apart. Labeled maintenance doses for weight management are 5 mg, 10 mg or 15 mg, and 15 mg is the maximum. Your prescriber may hold you at a dose longer if side effects are a problem.
Do I need to count units with Zepbound vials or pens?
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No. Branded Zepbound single-dose vials contain one fixed dose and you draw the whole contents, and the pens are pre-set. Unit math applies to compounded multi-dose vials, where you draw a measured part of the vial for each injection.
My dose is more than 100 units. What do I do?
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A standard 1 mL insulin syringe holds 100 units, so higher doses at a lower concentration won't fit in one draw. For example, 15 mg at 10 mg/mL is 150 units. Ask your prescriber or pharmacy about a higher-concentration vial rather than splitting injections on your own.
How many weeks will my tirzepatide vial last?
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Divide the total mg in the vial by your weekly dose. A vial holding 20 mg lasts 8 weeks at 2.5 mg but only 4 weeks at 5 mg. Remember that the vial also has a beyond-use date set by the pharmacy, which may arrive before the medication runs out.
Medical disclaimer: This calculator converts the numbers you enter; it does not choose or change your dose. The dose schedule shown is the FDA-labeled escalation for branded tirzepatide, and your prescriber may use a different one. Always follow your prescription and your pharmacy's label, and call the pharmacy if your calculated units don't match their instructions. Not medical advice.