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How-to · reconstitution
In this example, 3 mL of bacteriostatic water in a 30 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 | 30.00 mg/mL | 300 mcg | 8.3 units |
| 2 mL | 15.00 mg/mL | 150 mcg | 16.7 units |
| 3 mL | 10.00 mg/mL | 100 mcg | 25.0 units |
Straight arithmetic: concentration = 30 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 30 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 | 30.00 mg/mL | 8.3 units |
| 2 mL | 15.00 mg/mL | 16.7 units |
| 3 mL | 10.00 mg/mL | 25.0 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 | 30.00 mg/mL | 16.7 to 50.0 units |
| 2 mL | 15.00 mg/mL | 33.3 to 100.0 units |
| 3 mL | 10.00 mg/mL | 50.0 to 150.0 unitswon’t fit |
FDA labelZepbound (tirzepatide) — FDA-approved Prescribing Information · retrieved 2026-09-19
This vial contains twelve doses at the worked amount. With more drug in the same water volume, the draw becomes smaller; only one displayed row ends on a whole unit.
Compared with the smaller vial sizes, this example puts more medication into each unit of liquid. Using a remembered syringe reading from a weaker mixture would therefore give a different amount of drug.
Read the concentration and dose beside the unit result. Those values explain what the syringe number means and let you check whether you have selected the correct vial strength.
Two displayed calculations end between the illustrated syringe lines. The third ends on a whole unit. That is a mathematical difference, not evidence that a particular mixture has been tested for this product.
Use the prescribed preparation instructions rather than picking a row solely because it looks easier to read. If your concentration differs from all three rows, enter the actual values in the calculator instead of choosing the closest example.
The theoretical count assumes a constant dose and no loss while drawing. It also does not say whether the dispensed vial supports repeated use or will remain within its use-by date until the last dose.
Those details are needed before estimating actual cost per usable dose. A larger vial size does not establish those limits or show whether the vial is cheaper, wasteful or appropriate for a particular stage of treatment.
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.