Oliguria and anuria are the decreased or absent production of urine, respectively.

Oliguria is defined as a urine output that is less than 1 mL/kg/h in infants,^[1] less than 0.5 mL/kg/h in children,^[1] and less than 400 mL^[1] or 500 mL^[2] per 24h in adults – this equals 17 or 21 mL/hour. For example, in an adult weighing 70 kg it equals 0.24 or 0.3 ml/hour/kg. Alternatively, however, the value of 0.5 mL/kg/h is commonly used to define oliguria in adults as well.^[2]

Olig- (or oligo-) is a Greek prefix meaning small or few.^[3]

Anuria is defined as less than 50mL urine output per day.