What is the typical urine output target for an adult to indicate adequate kidney perfusion?

• A. About 0.2 mL/kg/hour
• B. About 0.5 mL/kg/hour
• C. About 1.0 mL/kg/hour
• D. About 2.0 mL/kg/hour

Answer: (B)

In adults, urine output reflects kidney perfusion and filtration activity. The typical target indicating adequate perfusion is about 0.5 mL per kilogram of body weight per hour. For a 70 kg person, that’s roughly 35 mL per hour. This rate is used in clinical care as a practical lower bound to ensure the kidneys are receiving enough blood flow to function and avoid acute kidney injury during resuscitation and critical illness. If urine output falls below this threshold, it suggests inadequate perfusion and prompts reassessment of fluids, blood pressure, and overall perfusion.

The other values are not the standard adequacy target. A much lower rate (0.2 mL/kg/hour) would signal substantial under-perfusion. A rate around 1.0 mL/kg/hour is higher than the minimal adequacy target and could occur with diuresis or good perfusion, but it’s not the typical benchmark used to judge adequacy. A rate of 2.0 mL/kg/hour is even higher and not the usual baseline indicator of adequate perfusion.