Tirzepatide reconstitution calculator
the API in Mounjaro® / Zepbound®
Tirzepatide is a dual GIP/GLP-1 agonist approved by the FDA in pen form. Vial-and-syringe use persists through compounding channels, where unit-conversion errors are the dominant safety failure the FDA has documented for this drug class.
Enter vial size, water volume, and the dose your provider gave you.
This tool converts the numbers you enter (dose ÷ concentration = volume). It never suggests a dose. The FDA has documented hospitalizations caused by mg / ml / unit conversion errors with vial-and-syringe products. If the readout surprises you, stop and verify with your prescriber or pharmacist.
Questions people actually search
How many units is 2.5 mg of tirzepatide?
It depends on the vial concentration. A 10 mg vial reconstituted with 2 ml is 5 mg/ml, so 2.5 mg = 0.5 ml = 50 units. The same dose from a 20 mg vial in 2 ml (10 mg/ml) is only 25 units. Always compute from the mg and ml on your specific vial.
Is compounded tirzepatide still available?
The FDA shortage that permitted large-scale compounding ended in late 2024. Routine compounding is now restricted; limited exceptions exist (for example, genuine clinical need for a different formulation). Lilly's branded pens are the approved forms.
Why does my pharmacy vial say ml but my prescription says mg?
Prescriptions state the drug amount (mg); syringes measure volume (ml or units). Concentration is the bridge: volume = dose ÷ concentration. This calculator does that arithmetic and shows the units mark to draw to.
Does tirzepatide expire?
Yes, twice over. Branded pens carry a printed expiration date plus a room-temperature window (check the label; typically up to 21 days). Compounded vials carry a pharmacy beyond-use date, commonly 28 to 90 days refrigerated depending on formulation; once reconstituted from powder, the working convention is 28 days refrigerated. When the dates disagree with your memory, the vial loses.
How long does tirzepatide stay in your system?
Its half-life is about five days, and a drug is effectively cleared after roughly five half-lives, so around 25 days after the last injection. That long tail is why weekly dosing works and why side effects fade gradually rather than overnight after stopping.