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How-to · reconstitution
In this example, 1 mL of bacteriostatic water in a 10 mg Tirzepatide vial gives 10.00 mg/mL. An example 2.5 mg amount is then 25.0 units on a U-100 syringe.
This example lands on a syringe line. More water makes a weaker mix and a bigger draw. Less water makes a stronger mix and a smaller one. The amount of Tirzepatide stays the same. Use the diluent and volume specified for your product; the arithmetic alone does not choose them.
| Water added | Concentration | Per U-100 unit | Example: 2.5 mg = |
|---|---|---|---|
| 1 mL | 10.00 mg/mL | 100 mcg | 25.0 units |
| 2 mL | 5.00 mg/mL | 50 mcg | 50.0 units |
| 3 mL | 3.33 mg/mL | 33.33 mcg | 75.0 units |
Straight arithmetic: concentration = 10 mg ÷ liquid volume, and 1 U-100 unit = 0.01 mL. The example column shows the math at 2.5 mg; it is not a dose recommendation.
The table compares possible concentrations; it does not establish which diluent or volume suits your product. Follow its dispensing instructions.
“Hard to measure” means the example draw is below two U-100 units. “Won’t fit” means it exceeds this syringe’s capacity.
Tirzepatide is the drug in Zepbound and Mounjaro. It works on two gut hormone signals involved in appetite and blood sugar.
The table above uses one worked example. These are the published quantities, converted into marks on a U-100 barrel at each listed liquid volume for a 10 mg vial. Where a quantity was never studied by injection, the row says so.
2.5 mg once weekly for 4 weeks, under the skin.
| Water added | Concentration | Draw |
|---|---|---|
| 1 mL | 10.00 mg/mL | 25.0 units |
| 2 mL | 5.00 mg/mL | 50.0 units |
| 3 mL | 3.33 mg/mL | 75.0 units |
FDA labelZepbound (tirzepatide) — FDA-approved Prescribing Information · retrieved 2026-09-19
5–15 mg once weekly, under the skin. (5, 10, or 15 mg).
| Water added | Concentration | Draw, low to high |
|---|---|---|
| 1 mL | 10.00 mg/mL | 50.0 to 150.0 unitswon’t fit |
| 2 mL | 5.00 mg/mL | 100.0 to 300.0 unitswon’t fit |
| 3 mL | 3.33 mg/mL | 150.0 to 450.0 unitswon’t fit |
FDA labelZepbound (tirzepatide) — FDA-approved Prescribing Information · retrieved 2026-09-19
The vial contains four doses at the amount used in this example. All three displayed water volumes produce whole-unit readings on the illustrated U-100 scale.
The count comes from dividing the drug amount in the vial by the example dose. Adding more water changes the concentration and draw volume, but leaves that division unchanged. It does not add medication or create extra doses.
This is an ideal calculation before liquid left in the vial or syringe. The count is not a guarantee of how many complete doses a specific container will deliver.
Each row ends on a whole unit, so you can compare the three readings without rounding a fraction to the nearest line. More water means a larger draw for the same amount of drug.
A whole number does not confirm that the inputs match your vial. Check the strength, total liquid volume and syringe scale together. A unit number copied from another concentration can represent a different dose.
There is no universal storage period attached to this calculation. The correct limit depends on the product and its preparation, including whether the container is intended for repeated use.
Follow the dispensing instructions for storage and disposal. A date on the label takes precedence over how much solution remains. The table cannot determine stability from vial size, nor can it tell you that a larger or smaller vial would be a better purchase.
The calculator lets you enter your product’s vial strength and mixing volume, then shows the arithmetic for your syringe.
Open the Tirzepatide calculator →The arithmetic on this page is only half the question. These are the pages that carry the other half.