At a glance
| Mark on U-100, 1 mL | Volume | at 1 mg/mL | at 2 mg/mL | at 2.5 mg/mL | at 5 mg/mL | at 10 mg/mL |
|---|---|---|---|---|---|---|
| 5 units | 0.05 mL | 0.05 mg | 0.1 mg | 0.125 mg | 0.25 mg | 0.5 mg |
| 10 units | 0.1 mL | 0.1 mg | 0.2 mg | 0.25 mg | 0.5 mg | 1 mg |
| 20 units | 0.2 mL | 0.2 mg | 0.4 mg | 0.5 mg | 1 mg | 2 mg |
| 25 units | 0.25 mL | 0.25 mg | 0.5 mg | 0.625 mg | 1.25 mg | 2.5 mg |
| 40 units | 0.4 mL | 0.4 mg | 0.8 mg | 1 mg | 2 mg | 4 mg |
| 50 units | 0.5 mL | 0.5 mg | 1 mg | 1.25 mg | 2.5 mg | 5 mg |
| 100 units | 1 mL | 1 mg | 2 mg | 2.5 mg | 5 mg | 10 mg |
Arithmetic at the concentrations shown. The concentration on your own label is the one that counts; enter it in the calculator.
Why the milligrams depend on the pharmacy label
25 units is 0.25 mL, a quarter of a millilitre. From a semaglutide vial that is 0.25 mg at 1 mg/mL, 0.5 mg at 2 mg/mL, 0.625 mg at 2.5 mg/mL and 1.25 mg at 5 mg/mL. Notice that two of those, 0.625 and 1.25 mg, are not strengths on any label, and one, 0.5 mg at 2 mg/mL, is. A round number of units does not produce a round number of milligrams unless the concentration happens to cooperate, and pharmacies choose concentrations for their own reasons. Work in milligrams: confirm the dose in mg with your prescriber, read the mg/mL from your label, and let the mark be whatever the division gives. A related habit worth keeping: write the mg/mL from the label on the vial's box in large figures the day you collect it. When the next fill arrives at a different concentration, the mark changes and the box tells you why before the syringe does.
The mistake to watch for. 0.25 on a prescription means 0.25 mg. 25 units on a syringe means 0.25 mL. At 1 mg/mL they coincide; at every other concentration they do not. The coincidence is where the mistakes come from.