Diuresis () is the excretion of urine, especially when excessive (polyuria). The term collectively denotes the physiologic processes underpinning increased urine production by the kidneys during maintenance of fluid balance.

In healthy people, the drinking of extra water produces mild diuresis to maintain the body water balance. Many people with health issues, such as heart failure and kidney failure, need diuretic medications to help their kidneys deal with the fluid overload of edema. These drugs promote water loss via urine production. The concentrations of electrolytes in the blood are closely linked to fluid balance, so any action or problem involving fluid intake or output (such as polydipsia, polyuria, diarrhea, heat exhaustion, starting or changing doses of diuretics, and others) can require management of electrolytes, whether through self-care in mild cases or with help from health professionals in moderate or severe cases.