What is the minimum normal urine output for an average adult per hour?

• A. About 20 mL per hour.
• B. About 60 mL per hour.
• C. About 100 mL per hour.
• D. About 30 mL per hour.

Answer: (D)

Normal kidney function requires a minimal urine flow to reflect adequate perfusion and waste clearance. A practical target is about 0.5 mL of urine per kilogram of body weight per hour. For an average adult, this comes to roughly 30 mL per hour. This lower limit helps identify situations like dehydration, low blood volume, or early kidney dysfunction. Outputs around 60 mL per hour can occur in healthy people and are not unusual, but they exceed the minimum. A rate of 20 mL per hour is low and concerning, while 100 mL per hour is higher than the minimum and can occur with normal intake or higher fluid status. So, the minimum commonly cited hourly urine output is about 30 mL.