Is an estimated glomerular filtration rate of 31 mL/min/1.73 m² considered chronic kidney disease stage 4?

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Last updated: October 26, 2026 • View editorial policy

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Yes, an eGFR of 31 mL/min/1.73 m² is classified as CKD Stage 3b, not Stage 4.

CKD Stage 4 is defined as eGFR 15-29 mL/min/1.73 m², while an eGFR of 31 falls into Stage 3 (30-59 mL/min/1.73 m²), specifically Stage 3b (30-44 mL/min/1.73 m²). 1

CKD Staging by eGFR

The KDOQI/KDIGO classification system, which has been globally endorsed and remains the standard, defines CKD stages based on GFR thresholds 2, 1:

  • Stage 1: eGFR ≥90 mL/min/1.73 m² (with kidney damage markers)
  • Stage 2: eGFR 60-89 mL/min/1.73 m² (with kidney damage markers)
  • Stage 3: eGFR 30-59 mL/min/1.73 m² (moderate decrease)
    • Stage 3a: 45-59 mL/min/1.73 m²
    • Stage 3b: 30-44 mL/min/1.73 m²
  • Stage 4: eGFR 15-29 mL/min/1.73 m² (severe decrease)
  • Stage 5: eGFR <15 mL/min/1.73 m² (kidney failure)

Clinical Significance

An eGFR of 31 mL/min/1.73 m² represents severe kidney function impairment with loss of approximately 70% of normal kidney function 2. At this level, patients face significantly increased risks of:

  • Cardiovascular disease and mortality 3
  • Progression to kidney failure requiring replacement therapy 3
  • Complications requiring close monitoring and management 2

Important Caveats

The eGFR value alone requires context for accurate interpretation:

  • Duration: CKD diagnosis requires abnormalities persisting ≥3 months 2, 1
  • Age considerations: While some advocate for age-adjusted thresholds (particularly in elderly patients without proteinuria) 4, the current standard definition applies the same GFR thresholds regardless of age 2
  • Equation accuracy: eGFR equations (particularly CKD-EPI, EKFC, or LMR) may overestimate or underestimate true GFR in certain populations, including young adults, those with low BMI, or hypoalbuminemia 5, 6
  • Additional markers: Presence of albuminuria/proteinuria significantly impacts prognosis and should be assessed alongside eGFR 1

For clinical decision-making at borderline values or in high-risk populations, consider measuring GFR directly using iohexol clearance or similar methods rather than relying solely on estimated values 3, 5.

References

6
Research

Comparison of estimated glomerular filtration rate equations on prediction of mortality, kidney failure, and acute kidney injury.

Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association, 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.