At a glance
| Volume | U-100, 1 mL mark | U-100, 0.5 mL mark | U-40, 1 mL mark |
|---|---|---|---|
| 0.1 mL | 10 | 10 | 4 |
| 0.2 mL | 20 | 20 | 8 |
| 0.25 mL | 25 | 25 | 10 |
| 0.3 mL | 30 | 30 | 12 |
| 0.4 mL | 40 | 40 | 16 |
| 0.5 mL | 50 | 50 | 20 |
| 0.75 mL | 75 | does not fit | 30 |
| 1 mL | 100 | does not fit | 40 |
Arithmetic at the concentrations shown. The concentration on your own label is the one that counts; enter it in the calculator.
Why the marks mean volume
Fifty units matters beyond insulin because 0.5 mL is the fill volume of every Zepbound single-dose vial: the whole vial is the 50 mark on a U-100 syringe. For insulin itself, 50 units is a dose large enough that the 1 mL syringe is the usual choice, and the 0.5 mL syringe is exactly full. The U-40 scale cannot express it: 50 units would be 1.25 mL and the syringe holds 1 mL, which is one reason U-40 syringes stay with the veterinary insulins they were made for. The table gives the marks for volumes up to a full millilitre on all three syringes. One more place 50 units appears: as the largest mark on the 0.5 mL syringe, which some people read as the syringe's "100" because it is the end of the scale. It is not. The scale is the same on all three U-100 sizes; the barrels simply stop at 30, 50 or 100.
The mistake to watch for. The 50 mark on a 1 mL syringe and a full 0.5 mL syringe are the same draw. Reading a full 0.5 mL syringe as 100 units, because it is full, doubles the intended dose on paper and halves it in the barrel.