How to read a U-100 insulin syringe
Want the numbers for your own vial? Use the calculator. It works offline and nothing leaves your device.
What U-100 means
U-100 means the syringe is marked so that 100 units = 1 mL. So 1 unit is 0.01 mL, and 10 units is 0.10 mL. A unit on the syringe is a volume mark, not an amount of any substance. How much is in each unit depends on how you mixed the vial.
The three common sizes
| Syringe | Holds | Lines usually every |
|---|---|---|
| 0.3 mL | 30 units | 1 unit |
| 0.5 mL | 50 units | 1 unit |
| 1 mL | 100 units | 2 units |
Always read the barrel of your own syringe. Some brands add half-unit lines on small syringes. A smaller syringe has its lines further apart, so small amounts are easier to read.
Units to mL
| Units | mL |
|---|---|
| 5 | 0.05 mL |
| 10 | 0.10 mL |
| 25 | 0.25 mL |
| 50 | 0.50 mL |
| 100 | 1.00 mL |
Formula: mL = units ÷ 100, and units = mL × 100.
Reading the mark
- Read where the flat top edge of the plunger’s rubber tip (the edge nearest the needle) lines up with the scale.
- Hold the syringe at eye level so the lines don’t look shifted.
- Tap out air bubbles and push them out before you read the mark. Bubbles take up space.
- If your number falls between two lines, the calculator shows the nearest line. Changing how much water you mix with can make the amount land on a line.
- Very small draws (under about 2 units) are hard to measure accurately.