Tirzepatide dosage calculator: mg to units
Convert your prescribed tirzepatide dose from mg to units and mL on a U-100 syringe, for any vial strength.
Medically reviewed by Lindsay Short, NP-BC, Board-Certified Nurse Practitioner · last reviewed October 2026
Tirzepatide dose calculator
Enter the dose your prescriber gave you and the strength printed on your vial label. The calculator converts it to units on a U-100 insulin syringe.
Example: 2.5 mg from a 10 mg/mL vial = 25 units (0.25 mL). Enter your own prescribed dose and vial strength above.
This converts a dose you have already been prescribed. It does not recommend a dose. Always use the concentration printed on your pharmacy label. If the number here does not match what you were told, stop and call your prescriber before injecting.
Quick answer. Units on a U-100 syringe = (prescribed dose in mg ÷ vial strength in mg/mL) × 100. 2.5 mg is 50 units at 5 mg/mL, 25 units at 10 mg/mL and 12.5 units at 20 mg/mL. 5 mg is 100 units at 5 mg/mL, 50 units at 10 mg/mL and 25 units at 20 mg/mL.
Brand Zepbound or Mounjaro vial? Do not convert: follow its Instructions for Use (the whole 0.5 mL from a single-dose vial, 0.6 mL per dose from a multi-dose vial). Brand pens deliver a set dose. Always use the strength printed on your own vial label.
Tirzepatide units chart by vial strength
Built by the clinical team at OC Weight Loss and Med Spa, a licensed medical weight loss clinic in Mission Viejo, California. The same conversions as the calculator, for every standard dose step and the vial strengths pharmacies most often dispense. Find your prescribed dose on the left and your vial strength along the top. For the week-by-week schedule, see the tirzepatide dosage chart.
| Prescribed dose | 5 mg/mL vial | 10 mg/mL vial | 20 mg/mL vial |
|---|---|---|---|
| 2.5 mg | 50 units (0.5 mL) | 25 units (0.25 mL) | 12.5 units* (0.125 mL) |
| 5 mg | 100 units (1 mL) | 50 units (0.5 mL) | 25 units (0.25 mL) |
| 7.5 mg | 150 units (1.5 mL)more than a 1 mL syringe holds | 75 units (0.75 mL) | 37.5 units* (0.375 mL) |
| 10 mg | 200 units (2 mL)more than a 1 mL syringe holds | 100 units (1 mL) | 50 units (0.5 mL) |
| 12.5 mg | 250 units (2.5 mL)more than a 1 mL syringe holds | 125 units (1.25 mL)more than a 1 mL syringe holds | 62.5 units* (0.625 mL) |
| 15 mg | 300 units (3 mL)more than a 1 mL syringe holds | 150 units (1.5 mL)more than a 1 mL syringe holds | 75 units (0.75 mL) |
100-unit (1 mL) syringes are usually marked every 2 units; 30- and 50-unit syringes every unit.
* Not a whole unit, so it falls between the marks on most syringes. Do not round it on your own: ask your prescriber or pharmacist how to measure it.
Brand Zepbound and Mounjaro vials: measured in mL, not units
Brand tirzepatide comes as pens, single-dose vials, multi-dose vials and KwikPens. The vials are measured in milliliters by their Instructions for Use, so they need no conversion, but their labels are easy to misread as a strength.
| Presentation | What the label shows | How a dose is measured |
|---|---|---|
| Single-dose vial | 2.5, 5, 7.5, 10, 12.5 or 15 mg in 0.5 mL | Draw the whole 0.5 mL |
| Multi-dose vial | The total for 4 doses, from 10 mg/2.4 mL (2.5 mg doses) to 60 mg/2.4 mL (15 mg doses) | 0.6 mL per dose, as the Instructions for Use describe |
| Single-dose pen or KwikPen | The dose the pen delivers | Nothing to convert |
The large number on a multi-dose vial is the total in the vial, not mg per mL. Entering it as the strength gives less than half the prescribed dose.
How the conversion works
Tirzepatide is prescribed in milligrams (mg), but a vial is measured in milliliters (mL), and an insulin syringe is marked in units. On a U-100 syringe, 100 units fill 1 mL. So the conversion needs two numbers: the dose you were prescribed, and the concentration printed on your vial.
Units = dose (mg) ÷ concentration (mg/mL) × 100. For example, 2.5 mg from a 10 mg/mL vial is 0.25 mL, which is 25 units on a U-100 syringe.
The same dose from a different-strength vial is a different number of units, which is why a number copied from someone else's chart can be wrong for you. The FDA has received reports of patients taking five to 20 times their intended dose of compounded semaglutide after confusion between milligrams, milliliters and units.
Compounded tirzepatide and semaglutide are not FDA-approved. They are prepared by a licensed pharmacy for an individual patient, and their strength varies from pharmacy to pharmacy, which is exactly why the concentration on your own label is the number that matters. Brand pens (Zepbound, Mounjaro, Wegovy, Ozempic) deliver a fixed dose and need no conversion.
Checks before every injection
- Read the strength on the vial label, every time. A refill can come at a different strength.
- Confirm the syringe is U-100 and note its capacity (30, 50 or 100 units).
- If the result looks very different from your last dose, stop and call your prescriber.
- Keep a written record of the dose and units you drew each week.
Answers before you book
How many units is 2.5 mg of tirzepatide?
It depends on the strength printed on your vial. On a U-100 syringe, 2.5 mg is 50 units (0.5 mL) at 5 mg/mL, 25 units (0.25 mL) at 10 mg/mL, about 16.7 units (0.167 mL) at 15 mg/mL, 12.5 units (0.125 mL) at 20 mg/mL and 10 units (0.1 mL) at 25 mg/mL.
Is 2.5 mg of tirzepatide the same as 25 units?
Only when the vial is 10 mg/mL. 25 units is 0.25 mL, which holds 1.25 mg at 5 mg/mL, 2.5 mg at 10 mg/mL and 5 mg at 20 mg/mL.
How many units is 5 mg of tirzepatide?
100 units (1 mL) at 5 mg/mL, 50 units (0.5 mL) at 10 mg/mL, about 33.3 units (0.333 mL) at 15 mg/mL, 25 units (0.25 mL) at 20 mg/mL and 20 units (0.2 mL) at 25 mg/mL.
How many mg is 20 units of tirzepatide?
20 units is 0.2 mL. That is 1 mg at 5 mg/mL, 2 mg at 10 mg/mL, 3 mg at 15 mg/mL, 4 mg at 20 mg/mL and 5 mg at 25 mg/mL.
Is 20 units of tirzepatide a lot?
Units only measure volume. 20 units is 0.2 mL: 2 mg from a 10 mg/mL vial but 4 mg from a 20 mg/mL vial. Whether it is the right amount depends on the dose on your prescription, not the number of units.
My vial label shows a total, like "30 mg/2 mL". What strength do I enter?
Divide the total milligrams by the total milliliters. 30 mg/2 mL is 15 mg/mL, so 2.5 mg is about 16.7 units (0.167 mL). The calculator does this for you if you choose "My label shows total mg and total mL". If the label shows only a total, such as "10 mg", with no volume, ask your pharmacy for the strength in mg/mL before you draw a dose.
I have Zepbound or Mounjaro vials. Do I need this calculator?
No. Brand vials are measured in milliliters by their Instructions for Use. A single-dose vial holds one dose in 0.5 mL, and you draw the whole 0.5 mL. A multi-dose vial holds four doses of 0.6 mL each; the number on its label, such as 20 mg/2.4 mL, is the total in the vial, not the strength per mL. Follow the Instructions for Use, and ask your pharmacist if your syringe is marked only in units.
Do Zepbound or Mounjaro pens need this conversion?
No. Single-dose pens and KwikPens deliver the dose set by the pen, so there is nothing to convert.
What if my dose does not land on a syringe mark?
Some conversions fall between marks: 2.5 mg from a 15 mg/mL vial is 16.67 units. Do not round on your own. Ask your prescriber or pharmacist how to measure it; 30- and 50-unit syringes usually have finer marks than a 100-unit syringe.
What if the units are more than my syringe holds?
For example, 10 mg from a 5 mg/mL vial is 200 units (2 mL), twice what a 1 mL syringe holds. Do not split it into two draws on your own: check the dose and strength against your label, then ask your prescriber or pharmacist how it should be measured.
Does this calculator tell me what dose to take?
No. It only converts a dose your prescriber has already given you. Starting, increasing or holding a dose is a decision for your prescriber.
Why does my number differ from a chart I found online?
Charts assume a particular vial strength. Compounded tirzepatide is dispensed at different concentrations, so the same dose in mg can be a different number of units. Some charts also assume a brand vial, which is measured in mL, not units. Your label, not the chart, is the reference.
Sources and references
- Zepbound (tirzepatide) prescribing information, DailyMed, US National Library of Medicine
- Mounjaro (tirzepatide) prescribing information, DailyMed
- FDA: dosing errors associated with compounded injectable semaglutide products (alert to health care providers, compounders and patients, July 2024)
- FDA: FDA's concerns with unapproved GLP-1 drugs used for weight loss
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