Tirzepatide Dosage Calculator

Tirzepatide is the once-weekly injectable medicine in Mounjaro and Zepbound. When it comes in a vial, the dose in mg must be turned into a volume to draw. That takes one division, plus one multiplication for an insulin syringe.

What the Tirzepatide Dosage Calculator Measures

It measures volume, not dose. You bring the dose in mg from your prescription and the strength of your vial, and the calculator shows how many mL, and how many syringe units, hold that dose. It does not suggest, check or change doses. If your vial is a powder you mix first, the Peptide Calculator handles that step. For semaglutide, use the Semaglutide Dosage Calculator.

The Formula

Concentration (mg/mL) = mg in the vial / mL in the vial

Volume to draw (mL) = prescribed dose (mg) / concentration (mg/mL)

Units on a U-100 syringe = volume (mL) x 100

The "x 100" step works because U-100 means 100 units in each mL, so each unit mark is 0.01 mL¹.

How This Calculator Computes Your Result

Enter your prescribed dose in mg, then choose your vial. For a pharmacy vial, enter the label's mg/mL, or its total mg and total mL. For a Zepbound or Mounjaro vial, pick the printed strength. Each single-dose vial holds one dose in 0.5 mL, and each multi-dose vial holds 4 doses of 0.6 mL² ³.

The result shows every step, the volume to 3 decimals and the units to 1 decimal. If the units miss a whole mark, it shows the nearest mark and the dose it holds. An optional box checks the units or mL on your pharmacy instructions. A Lilly vial from the list only accepts its printed dose, since a single-dose vial gives one whole dose and is thrown away after use, even with medicine left⁴.

What Your Result Means

A unit is a mark on the syringe, not an amount of drug. The same 25 units holds 2.5 mg from a 10 mg/mL vial but 6.25 mg from a 25 mg/mL vial.

On Lilly's vials the volume is the same at every strength, so the dose depends on which vial you have. The labels measure in mL, with "a 1 mL syringe capable of measuring a 0.5 mL or 0.6 mL dose", and do not mention units² ⁴.

For pharmacy vials, the volume changes with strength. These examples show the math only, not specific products.

FDA Label Dosing Schedules for Mounjaro and Zepbound

This is label information for reference only. It is not used in the calculation, and your prescriber sets your dose. The Mounjaro label says the slow start and step-up are there to lower the risk of stomach and gut side effects³.

From the labels revised August 2026² ³. Check DailyMed for the current version.

Why Pen Users Do Not Need This Conversion

A single-dose pen holds one dose of a set strength in 0.5 mL, so there is nothing to measure². The KwikPen holds 4 fixed doses. You turn the dose knob until it stops, and the instructions say not to count clicks⁵. In both cases the pen's strength is the dose, so mL and units never come into it.

Compounded Tirzepatide and Dosing Errors

On December 19, 2024, FDA ruled the tirzepatide shortage resolved and gave pharmacies until February 18, 2025 and outsourcing facilities until March 19, 2025 to stop compounding under the shortage rules⁶. As of April 2026, tirzepatide is on neither FDA's shortage list nor its outsourcing facility bulks list, and pharmacies may not regularly make what are essentially copies of an approved drug unless a prescriber documents a significant difference for a specific patient⁷. On April 30, 2026, FDA also proposed formally excluding tirzepatide from that bulks list, finding no clinical need for outsourcing facilities to compound it from bulk substances⁸. Compounded drugs are not FDA approved, so FDA does not review their safety, effectiveness or quality before sale⁹.

In 2024, FDA warned of overdoses from compounded semaglutide vials, linked to confusion between mL, mg and "units"¹⁰. Some patients told to draw 5 units drew 50, some took 5 to 20 times the intended dose, and some needed hospital care¹⁰. FDA asked compounders to supply a syringe sized for the dose¹⁰. That alert named semaglutide, but the same mix-up can happen with any vial. As of May 31, 2026, FDA had received more than 730 adverse event reports linked to compounded tirzepatide⁹.