多尿症（英文：Polyuria）是指在一定时间内，所排出的尿量比一般高。

如果饮水量为2000毫升，正常人的尿量介于800毫升－2000毫升。

如果所排出的尿量在一天内高于2500毫升，便是多尿症。

Anuria means nonpassage of urine, in practice is defined as passage of less than 100 milliliters of urine in a day. Anuria is often caused by failure in the function of kidneys. It may also occur because of some severe obstruction like kidney stones or tumours. It may occur with end stage renal disease. It is a more extreme reduction than oliguria, sometimes called anuresis.