What is the normal urine output for a healthy adult over 24 hours?

Normal 24-Hour Urine Output in Healthy Adults

A healthy adult should produce approximately 800-2000 mL (0.8-2 liters) of urine per 24 hours, with the minimum acceptable output being at least 0.5 mL/kg/hour (approximately 840 mL/day for a 70 kg person). 1, 2

Standard Thresholds

The minimum normal urine output is 0.5 mL/kg/hour sustained over 24 hours, which translates to:

• For a 70 kg adult: 35 mL/hour or 840 mL/day minimum 2
• Upper range can extend to 3000 mL/day depending on fluid intake 3
• Practical target: approximately 1 liter per day for patients with normal renal function not receiving diuretics 2

Clinical Context and Fluid Intake Relationship

The 24-hour urine volume directly reflects total water intake and hydration status. Research demonstrates that:

• Total water intake of 3.7 L/day in men and 2.7 L/day in women (per National Academy of Medicine guidelines) maintains optimal hydration 4
• A 24-hour urine osmolality ≤500 mOsm/kg indicates adequate hydration, which corresponds to sufficient urine output to compensate for daily losses and reduce risk of kidney stones and chronic kidney disease 5
• During water restriction to 1.0 liter/24 hours, urine volume decreases to approximately 770 mL/24 hours 6
• During water loading to 6.8 liters/24 hours, urine volume increases to approximately 6000 mL/24 hours 6

When Urine Output Becomes Concerning

Oliguria (abnormally low output) is defined as <0.5 mL/kg/hour for at least 6 hours, which equals:

• <840 mL/day for a 70 kg person 1
• The traditional clinical threshold is <400 mL/day 1

Severe oliguria requiring immediate intervention is <4 mL/kg over 8 hours (approximately <280 mL/8 hours for a 70 kg person) 1

Important Clinical Caveats

Urine output measurements become unreliable in specific populations:

• Patients receiving diuretics: Output is artificially increased without reflecting true kidney function 1, 2
• Cirrhotic patients with ascites: May be oliguric due to sodium retention despite normal kidney function 1, 2
• Obese patients: Weight-based calculations become problematic; consider using adjusted body weight 1

The 24-hour urine collection is more informative than random spot measurements, though cumbersome. Completeness can be verified by measuring urinary creatinine (men should excrete >15 mg/kg/day, women >10 mg/kg/day) 3