Glossary
Dead space
Also written dead volume, residual volume
The liquid left in a syringe's hub and needle after the plunger is fully depressed. Small, and it comes out of every dose.
On an insulin syringe with a fixed needle, dead space is minimal by design, a few thousandths of a millilitre. On a syringe with a detachable needle it is considerably larger, and at the volumes used here that is a real fraction of a small dose.
It matters most when the dose itself is tiny. Losing 0.01 mL from a 0.05 mL draw is a fifth of the dose; from a 1 mL draw it is a rounding error.
It is one reason insulin syringes are the standard tool for this, alongside their scale being fine enough to measure the volumes involved.
Related terms