What is the recommended urine output goal in mL per kilogram per hour for an adult?

Goal Urine Output for Adults

The recommended minimum urine output goal for adults is ≥0.5 mL/kg/hour, which translates to approximately 840 mL/day for a 70 kg patient. 1, 2

Standard Thresholds and Clinical Targets

• Normal urine output is defined as ≥0.5 mL/kg/hour in adults, which serves as both the physiologic baseline and the minimum acceptable target during fluid resuscitation and critical care management 1, 2

• For a 70 kg patient, this threshold equals:

  • 35 mL/hour (0.5 mL/kg/h × 70 kg)
  • 840 mL/day minimum acceptable output 1, 2

• Patients with normal renal function who are not receiving diuretics should maintain at least 0.8-1.0 L per day 1, 2

Critical Action Thresholds for Acute Kidney Injury

The duration and severity of reduced urine output define AKI staging, with progressively worse outcomes at each stage 3, 1:

• Stage 1 AKI: <0.5 mL/kg/hour for 6-12 hours 3, 1
• Stage 2 AKI: <0.5 mL/kg/hour for ≥12 hours 3, 1
• Stage 3 AKI: <0.3 mL/kg/hour for ≥24 hours OR anuria for ≥12 hours 3, 1

An absolute indication to suspend nephrotoxic therapies (such as high-dose IL-2) is urine output <4 mL/kg over 8 hours, representing severe oliguria requiring immediate intervention 3, 1

Context-Specific Targets

During IL-2 Therapy or Nephrotoxic Treatment

• Maintain urine output of at least 0.5 mL/kg/hour prior to each dose 3
• Hold therapy if urine output falls below 4 mL/kg over 8 hours 3, 1
• Check urine output 2 hours prior to first dose to address abnormalities proactively 3

During Fluid Resuscitation

• Target urine output of 100-150 mL/hour in patients with acute kidney injury or at risk for AKI (such as those with multiple myeloma and renal disease) 3
• For septic or tachycardic patients, start with a 20 mL/kg bolus and reassess urine output after 30-60 minutes 1
• If output remains <50-80 mL/hour after initial bolus, consider repeating 500 mL bolus 1

Perioperative Setting

Emerging evidence suggests that a lower target of 0.2 mL/kg/hour may be safe and fluid-sparing in patients undergoing major abdominal surgery without significant kidney injury risk factors, resulting in substantially less intravenous fluid administration (3170 mL vs 5490 mL) without compromising renal function markers 4. However, this lower target should only be applied in carefully selected surgical patients without AKI risk factors, not as a general standard 4.

Important Clinical Pitfalls and Caveats

When Urine Output Becomes Unreliable

Diuretic administration invalidates urine output thresholds because these medications artificially increase output without improving kidney function 1, 2. In patients receiving diuretics, urine output cannot be used as the sole criterion for assessing renal function 1.

In cirrhotic patients with ascites, urine output is problematic as a diagnostic criterion because these patients are frequently oliguric with avid sodium retention but may maintain relatively normal GFR 3, 1. Diuretic treatment can artificially increase output, and urine collection is often inaccurate in this population 3, 1.

Obesity Considerations

The standard mL/kg/hour formula becomes problematic in obese patients due to nonlinear relationships between body weight and expected urine output 2, 5. Consider using adjusted body weight for calculations in this population 2, 5.

Fluid Management Strategy

The fluid administration rate should exceed the sum of current urine output, estimated insensible losses (30-50 mL/hour), and gastrointestinal losses 1. Avoid fluid overload by calculating replacement needs accurately rather than administering large empirical volumes 1.

In patients with heart failure and reduced ejection fraction, completely avoid rapid boluses and use conservative maintenance rates (50 mL/hour initially, targeting 1-1.5 mL/kg/hour) 1.

Controversial Evidence on Targeting Urine Output

There is insufficient evidence that actively targeting urine output as a goal in fluid management protocols improves mortality, and some data suggest it may paradoxically increase mortality when used as a primary endpoint in goal-directed therapy 6. This suggests that while monitoring urine output is essential for detecting kidney injury, aggressively chasing urine output targets with excessive fluid administration may be harmful 6.

However, a 6-hour urine output threshold of 0.3 mL/kg/hour (rather than the standard 0.5 mL/kg/hour) was independently predictive of both hospital mortality and 1-year mortality in one prospective ICU study, suggesting the current AKI definition may be too liberal 7. This lower threshold was associated with a stepped increase in mortality (from 10% above to 30% below 0.3 mL/kg/hour) 7.