The primary mechanism used by cells to maintain water balance between themselves and their surrounding environment is called osmoregulation. Osmoregulation is the active regulation of fluid and electrolyte movement in and out of a cell or body and is accomplished by the kidneys. When you are dehydrated, the kidneys create super-concentrated urine,. And if you drink too much and therefore have fluid overload, your kidneys can alter their role and cause diuresis, or the increased release of urine, in order to get rid of excess fluid.