The error this tool prevents
Zepbound pens deliver a fixed dose; compounded tirzepatide vials do not. The patient draws the dose with an insulin syringe marked in units, where 100 units equals 1 mL. Because vial concentrations differ, the same milligram dose corresponds to different unit counts on different vials, and a unit count copied from a forum, a friend, or a previous vial can be several times too high. The FDA's safety communications describe overdoses requiring hospitalization from exactly this confusion.
How to use it
Enter the dose your clinician prescribed and the concentration printed on your vial in mg/mL. The tool returns the volume in mL and units. Check it against your pharmacy's written instructions before every new vial. If the label lacks a concentration or lists a salt form, stop and ask the pharmacy. Optionally enter the total mg in the vial to see how many doses it contains, which helps with refill timing.
What it will not do
It will not recommend or escalate a dose. The labeled Zepbound titration is shown for reference. Dose decisions belong to your prescriber.