Glossary
Unit
Also written units, IU, insulin unit
A mark printed on an insulin syringe. A unit is not a fixed volume. What it represents depends entirely on the syringe's scale.
On a U-100 syringe, one unit is 0.01 mL, so 100 units make up a millilitre. On a U-40 syringe, one unit is 0.025 mL. The same mark on the two barrels holds two and a half times as much liquid.
This is why a dose expressed only in units is incomplete information, and why every figure this site produces names the syringe it belongs to. Confusing the two scales is one of the documented sources of serious dosing errors.
Related terms