Tools
Your dose in units
Reviewed August 2026
Quick answer
A prescription is written in milligrams. A U-100 syringe is marked in units, which are hundredths of a millilitre. To get from one to the other you need the concentration of your own vial — and that is set by the pharmacy that made it, so it differs between sellers. Two vials of the same dose can be two different marks.
This converts two numbers you already have. It does not decide what dose you should take, and it cannot tell you what is in your vial — read that off the label, and if the label and this page disagree, the label is the label. Anything unclear is a question for the pharmacy that dispensed it.
What is on your vial
Read it off the label in front of you. A vial labelled “10 mg per mL” is 10. If it gives a total and a volume instead — say 60 mg in 3 mL — divide: that is 20.
The number your prescriber set. This tool converts it; it does not choose it.
Units on a U-100 syringe
Put in the strength printed on your vial and the dose you were prescribed. The mark on the syringe appears here.
A U-100 syringe is marked in hundredths of a millilitre, so 100 units is 1 mL. If yours is marked differently, this number does not apply to it.
Why the two numbers differ
Milligrams measure how much medication there is. Units measure how much liquid you are drawing. A vial holds the medication dissolved in liquid, and the concentration is the exchange rate between them.
Double the concentration and the same dose becomes half the liquid. That is the entire reason a dose can be “20 units” at one seller and “40 units” at another while being the same amount of drug.
What this cannot tell you
It has no idea what is in your vial. It takes the concentration you type and does arithmetic on it — so a mistyped strength produces a confident wrong answer, and the only protection against that is reading the label rather than remembering it.
It also does not know your syringe. The number here is for a U-100 syringe, marked to 100 units per millilitre. A syringe marked differently needs a different sum.
The approved product, as a worked example
| Dose | Concentration | Volume | Units, U-100 |
|---|---|---|---|
| 2.5 mg | 4.17 mg/mL | 0.60 mL | 60 |
| 5 mg | 8.33 mg/mL | 0.60 mL | 60 |
| 7.5 mg | 12.5 mg/mL | 0.60 mL | 60 |
| 10 mg | 16.7 mg/mL | 0.60 mL | 60 |
| 12.5 mg | 20.8 mg/mL | 0.60 mL | 60 |
| 15 mg | 25 mg/mL | 0.60 mL | 60 |
The same dose is a different mark on a different vial, which is why switching sellers changes the number even when the milligrams stay the same.
Concentrations from the FDA prescribing information for ZEPBOUND (tirzepatide), revision 4/2026. DailyMed. A compounded vial is not this product and carries its own strength.