Tirzepatide Reconstitution Calculator
Reconstituting compounded tirzepatide? Enter your vial size, your weekly dose, and the bacteriostatic water you're adding — this free tirzepatide reconstitution calculator returns the exact units to draw on an insulin syringe, your vial's concentration, and how many weekly doses the vial holds.
100 units per mL — pick the syringe you have.
Draw to
BAC water
on a U-100 insulin syringe
Drag the syringe to set your dose, or type the values above.
Enter your vial amount and dose, then type the bacteriostatic water or drag the syringe to see the exact units to draw.
Chips and prefilled values are commonly used numbers shown for convenience — not recommendations. Enter your own vial, dose, and water.
Never do this math twice.
The Pep AI app remembers your vials and doses, shows an interactive syringe you draw to, counts down the doses left in each vial, and reminds you when it's time. Free on iOS and Android.
How tirzepatide reconstitution works
Compounded tirzepatide ships as a lyophilized powder you mix with bacteriostatic water. The math from vial to syringe is three steps, and the calculator runs all of them:
1. Concentration
Vial amount ÷ water added. A 20 mg vial with 2 mL of water is 10 mg/mL.
2. Volume per dose
Your dose ÷ concentration. A 2.5 mg dose at 10 mg/mL is 0.25 mL.
3. Units to draw
Volume per dose × 100 for a U-100 syringe (or × 40 for a U-40). 0.25 mL on a U-100 syringe is 25 units.
Worked example
You have a 20 mg vial, you want a 2.5 mg dose, and you add 2 mL of bacteriostatic water. Concentration is 20 ÷ 2 = 10 mg/mL. Volume per dose is 2.5 ÷ 10 = 0.25 mL. On a U-100 syringe that's 0.25 × 100 = 25 units, and the vial holds 8 doses.
What's different about tirzepatide
Tirzepatide runs on bigger numbers than semaglutide: doses titrate from 2.5 mg up to 15 mg weekly, and compounded vials are correspondingly larger — 10, 20, 30, even 60 mg. That changes the reconstitution trade-off. With a high weekly dose and a generous amount of water, the volume per dose can get close to (or past) what a 1 mL insulin syringe holds.
That's the warning to watch for in the calculator: if your draw exceeds 100 units on a U-100 syringe, it won't fit in one draw. The fix is either less bacteriostatic water (a more concentrated vial) or a larger syringe. On the flip side, very little water makes low starting doses hard to read on the syringe — at 2.5 mg from a concentrated vial you may be drawing just a few units.
Tracking helps here too: the Pep AI app stores your vial and reconstitution once, converts each titration step to units automatically, and reminds you on shot day — the tirzepatide tracker covers the whole routine.
Frequently asked questions
This calculator is provided for informational and educational purposes only and is not medical advice. Always confirm dosing with a qualified healthcare professional and double-check your own measurements before administering anything.