U or u** medical abbreviation, what is the meaning of it?

U or u** medical abbreviation, what does it mean? In medicine, the medical abbreviation U or u** stands for Unit. Mistaken as the number 0 or 4, causing a 10-fold overdose or greater (for example, 4U seen as “40” or 4u seen as “44”); mistaken as “cc” so the dose is given in volume instead of units.