Oliguria is a medical term that refers to low urine output, which is defined as less than 400 milliliters (mL) to 500 mL of urine per 24 hours in adults. The specific amounts for infants and children are based on their weight, with less than 1 mL/kilogram (kg)/hour for infants and less than 0.5 mL/kg/hr for children. Oliguria can be caused by a variety of factors, including dehydration, kidney diseases, heart or lung diseases, blockages, and trauma. The best way to treat oliguria depends on the underlying cause, but it may involve drinking more fluids, taking medications, or undergoing renal replacement therapy like dialysis. Oliguria can be a sign of an underlying disorder and requires prompt diagnosis and treatment to avoid complications.