Insulin syringe unit conversion (revision 2)

An insulin syringe unit is a graduation on a syringe barrel calibrated for insulin of a stated concentration. On the U-100 scale, which is the international standard for human insulin, 100 units correspond to exactly 1 millilitre, so one unit is 0.01 mL.^[1] The unit is therefore a volume, and the mass of any substance it contains depends entirely on the concentration of the solution in the barrel.

This is the single most consequential fact on this page, and the source of the errors it exists to prevent. A "10 unit dose" is a statement about volume; it means 0.1 mL, and it says nothing about milligrams until a concentration is supplied. Where a solution has been reconstituted by the user rather than filled by a manufacturer, no syringe marking can carry information about its strength.