What is the medical term meaning when blood cells shrink?

The medical term meaning when blood cells shrink is crenation. Crenation is a process in which red blood cells (RBCs) lose water and become smaller and more dense. This can happen when RBCs are exposed to a hypertonic solution, which is a solution with a higher concentration of solutes than the RBCs. Crenation can also occur when RBCs are damaged or diseased, such as in the case of sickle cell anemia.