Page last checked
How-to · reconstitution
In this example, 1 mL of bacteriostatic water in a 5 mg Tirzepatide vial gives 5.00 mg/mL. An example 2.5 mg amount is then 50.0 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 | 5.00 mg/mL | 50 mcg | 50.0 units |
| 2 mL | 2.50 mg/mL | 25 mcg | 100.0 units |
| 3 mL | 1.67 mg/mL | 16.67 mcg | 150.0 unitswon’t fit |
Straight arithmetic: concentration = 5 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 5 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 | 5.00 mg/mL | 50.0 units |
| 2 mL | 2.50 mg/mL | 100.0 units |
| 3 mL | 1.67 mg/mL | 150.0 unitswon’t fit |
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 | 5.00 mg/mL | 100.0 to 300.0 unitswon’t fit |
| 2 mL | 2.50 mg/mL | 200.0 to 600.0 unitswon’t fit |
| 3 mL | 1.67 mg/mL | 300.0 to 900.0 unitswon’t fit |
FDA labelZepbound (tirzepatide) — FDA-approved Prescribing Information · retrieved 2026-09-19
This example divides the vial into two doses. Two of the three water amounts fit the illustrated U-100 barrel; the largest amount produces a draw beyond its capacity.
With the same amount of drug spread through more liquid, each dose takes up more space. Here the largest water amount puts the result past the end of the illustrated syringe. That row is a calculation warning, not a suggestion to fill beyond the scale.
The other rows show how the draw changes when the concentration changes. Whether either volume is suitable for a particular product still depends on its mixing instructions.
Dividing the vial content by the example dose gives two complete doses before any handling losses. It does not establish that a vial can be opened twice or kept for a later visit.
Check whether the dispensed container is labeled for single or repeated use. Its instructions determine what happens to any remaining solution; the ingredient name alone cannot set that date.
This is the smallest tirzepatide vial size in these calculation guides. A larger entered dose reduces the number of complete doses it contains, and a dose larger than the entire vial cannot be drawn from it.
Use the prescribed amount and the concentration on the dispensing label when checking an actual draw. The worked amount here explains the conversion; it does not select a vial or a treatment schedule.
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.