Picking a water volume
A 20mg tirzepatide vial can be reconstituted with different water volumes depending on what concentration is most convenient for your typical doses. Common choices range from 1mL to 4mL, giving concentrations from 20mg/mL down to 5mg/mL.
What each common ratio looks like
2mL of water gives 10mg/mL. 4mL gives 5mg/mL. A more concentrated mix (less water) means smaller unit draws per dose; a more dilute mix means larger, sometimes easier to measure precisely, draws.
A worked example at 10mg/mL
Mixed with 2mL (10mg/mL), a 2.5mg dose is drawn as 2.5 ÷ 10 × 100 = 25 units. A 5mg dose would be 50 units. These numbers only apply to this specific 2mL mix; a different water volume changes every unit figure.
Why matching the ratio to your dose matters
Choosing a water volume that produces clean, easy-to-read unit numbers for your actual dose steps reduces the chance of a measurement error and makes it easier to double-check a draw at a glance.
Before injecting
Confirm the water volume actually used against what’s written on the vial, recalculate rather than relying on memory, and check the solution looks clear with no visible particles before drawing a dose.