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How-to · reconstitution
In this example, 1 mL of bacteriostatic water in a 60 mg Tirzepatide vial gives 60.00 mg/mL. An example 2.5 mg amount is then 4.2 units on a U-100 syringe.
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 | 60.00 mg/mL | 600 mcg | 4.2 units |
| 2 mL | 30.00 mg/mL | 300 mcg | 8.3 units |
| 3 mL | 20.00 mg/mL | 200 mcg | 12.5 units |
Straight arithmetic: concentration = 60 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 60 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 | 60.00 mg/mL | 4.2 units |
| 2 mL | 30.00 mg/mL | 8.3 units |
| 3 mL | 20.00 mg/mL | 12.5 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 | 60.00 mg/mL | 8.3 to 25.0 units |
| 2 mL | 30.00 mg/mL | 16.7 to 50.0 units |
| 3 mL | 20.00 mg/mL | 25.0 to 75.0 units |
FDA labelZepbound (tirzepatide) — FDA-approved Prescribing Information · retrieved 2026-09-19
The largest tirzepatide vial shown here divides into twenty-four worked doses. Every displayed water amount produces a fractional reading on the illustrated whole-unit syringe scale.
All three calculations fall between the lines drawn on this scale. Adding more water increases the draw, but none of the displayed volumes makes it a whole number. The table keeps those fractions rather than silently changing the dose.
Compare the exact result with the markings on the actual syringe. If the result cannot be measured with the supplied equipment, the dispensing pharmacist needs to clarify the preparation or measurement.
At a fixed dose and water volume, this larger vial produces a more concentrated solution and therefore a smaller draw. The total amount in the vial and the volume of one injection move in different directions.
This is why a unit count from a smaller vial cannot be reused on its own. It needs the matching concentration, even when both containers have the same ingredient name.
The example divides the total drug by one unchanged dose. It does not establish a treatment duration, a storage limit or the number of doses recoverable after handling losses.
The dispensing label determines whether and how the prepared product can be kept. No expiry or waste estimate is assigned here from a general vial rule. A large dose count alone also cannot establish value for money or suitability for your prescription.
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.