What urine output (mL/kg per hour) should be targeted in adults and children with acute kidney injury or rhabdomyolysis?

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Last updated: November 1, 2026 • View editorial policy

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Targeted Urine Output in AKI and Rhabdomyolysis

For adults with acute kidney injury, maintain urine output >0.5 mL/kg/h, though emerging evidence suggests targeting >1.0 mL/kg/h may reduce AKI progression; for rhabdomyolysis specifically, target ≥300 mL/h (approximately 3-4 mL/kg/h in a 70-80 kg adult) for at least the first 24 hours. 1, 2

Standard AKI Monitoring Thresholds

The KDIGO guidelines establish urine output thresholds primarily for diagnosing and staging AKI, not as therapeutic targets 1:

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

These are diagnostic criteria that define when oliguria becomes clinically significant, not necessarily the output you should target therapeutically.

Emerging Evidence for Higher Targets in General AKI

Recent high-quality research challenges the traditional 0.5 mL/kg/h threshold:

  • A 2024 MIMIC-IV study (n=35,845) demonstrated that urine output <0.2-0.3 mL/kg/h over 6 hours better predicted mortality than the KDIGO 0.5 mL/kg/h threshold, with superior discrimination (AUC 0.75 vs 0.69) 3

  • A 2025 multicenter sepsis study found that urine output >1.0 mL/kg/h on the day of sepsis diagnosis was associated with lower AKI incidence (43.6% vs 56.5%, p=0.028), with cubic spline analysis suggesting an optimal threshold of 1.2-1.3 mL/kg/h for AKI prevention 4

Clinical implication: While 0.5 mL/kg/h remains the standard monitoring threshold, maintaining higher urine output (>1.0 mL/kg/h) when feasible may reduce AKI progression in critically ill adults, particularly those with sepsis.

Rhabdomyolysis: A Critical Exception

Rhabdomyolysis requires substantially higher urine output targets to prevent myoglobin-induced tubular injury 2:

  • Target: ≥300 mL/h in adults for at least the first 24 hours
  • This translates to approximately 3-4 mL/kg/h for a 70-80 kg adult—substantially higher than standard AKI thresholds
  • Aggressive fluid resuscitation should begin within 6 hours of muscle injury when possible

Rationale for Higher Targets in Rhabdomyolysis

The pathophysiology differs fundamentally from other AKI causes 2, 5:

  • Myoglobin precipitates in acidic urine, causing tubular obstruction
  • High urine flow rates prevent myoglobin cast formation
  • Dilution reduces myoglobin concentration below nephrotoxic thresholds
  • Early aggressive hydration (within 6 hours) significantly reduces AKI risk

Practical Approach to Rhabdomyolysis

  1. Initiate aggressive IV fluid resuscitation immediately (preferably within 6 hours)
  2. Target urine output ≥300 mL/h for the first 24 hours minimum
  3. Monitor for fluid overload, especially in elderly or those with cardiac disease
  4. Consider sodium bicarbonate only if systemic acidosis is present (not routinely for urine alkalinization, as evidence is lacking) 2
  5. Use mannitol only if adequate fluids fail to achieve target urine output, not routinely

Pediatric Considerations

For children with AKI, the evidence is more nuanced:

  • Neonates: Recent 2024 cardiac surgery data suggests higher thresholds (3.0,2.0,1.0 mL/kg/h for stages 1-3) outperform standard KDIGO criteria 6
  • Children 1-24 months: Standard adult KDIGO thresholds (0.5 mL/kg/h) appear appropriate and were validated in the same study 6
  • Children on CKRT: Urine output ≥0.41 mL/kg/h on day 14 predicted dialysis independence with 97% post-test probability 7

Common Pitfalls to Avoid

  1. Don't confuse diagnostic thresholds with therapeutic targets: The 0.5 mL/kg/h threshold defines oliguria for AKI staging but isn't necessarily the output you should aim for therapeutically

  2. Don't undertarget in rhabdomyolysis: The 300 mL/h target (3-4 mL/kg/h) is 6-8 times higher than standard AKI thresholds—this is intentional and necessary

  3. Don't delay fluid resuscitation in rhabdomyolysis: Every hour of delay increases AKI risk; start fluids immediately upon recognition 2

  4. Don't routinely alkalinize urine in rhabdomyolysis: Despite historical practice, no controlled trials demonstrate benefit of sodium bicarbonate over fluids alone; use it only for systemic acidosis 2

  5. Monitor for fluid overload: Aggressive fluid targets (especially 300 mL/h in rhabdomyolysis) require careful monitoring for pulmonary edema and volume overload, particularly in elderly patients or those with heart failure

References

7
Research

Urine Output Trajectories and Dialysis Independence in Critically Ill Children With Acute Kidney Injury: A Single-Center Retrospective Cohort Study, 2014-2023.

Pediatric critical care medicine : a journal of the Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies, 2025

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.