At a glance
| Concentration | 5 mg is | Mark on U-100, 1 mL |
|---|---|---|
| 2.5 mg/mL | 2 mL | does not fit (over 1 mL) |
| 5 mg/mL | 1 mL | 100 |
| 8.33 mg/mL | 0.6 mL | 60 (exactly 60.02) |
| 10 mg/mL | 0.5 mL | 50 |
| 20 mg/mL | 0.25 mL | 25 |
| 25 mg/mL | 0.2 mL | 20 |
Arithmetic at the concentrations shown. The concentration on your own label is the one that counts; enter it in the calculator.
Why the answer depends on the label
Five milligrams is a dose that sits right at the edge of what an insulin syringe can hold, which makes the concentration decisive. At 5 mg/mL it is the entire 1 mL barrel, the 100 mark, with nothing to spare. At 2.5 mg/mL it is 2 mL and cannot be drawn in one insulin syringe; the calculator refuses it rather than suggesting two draws. At 10 mg/mL it is a comfortable 50 units, and at 20 or 25 mg/mL it is small enough to read on a 0.5 mL syringe. For a powder vial you reconstitute yourself, the liquid you add sets this: 10 mg with 1 mL added is 10 mg/mL and 5 mg is 50 units; 10 mg with 2 mL is 5 mg/mL and 5 mg is the whole barrel. If your label is in micrograms, 5 mg is 5,000 mcg.
The mistake to watch for. When 5 mg comes out to the 100 mark, a slightly higher concentration on the next vial makes the draw fit, and a slightly lower one makes it impossible. Read the mg/mL on each vial rather than reusing last month's mark.