Normal GFR Levels
Normal GFR values are approximately 100-130 mL/min/1.73 m² in young men and 90-120 mL/min/1.73 m² in young women, with physiological decline beginning after age 40 years. 1
Age and Sex-Specific Normal Values
Young Adults (Under 40 Years)
- Men: Normal GFR ranges from approximately 120-130 mL/min/1.73 m² in young adults 1
- Women: Normal GFR ranges from approximately 90-120 mL/min/1.73 m² in young women 1
- Mean GFR remains stable at approximately 107 mL/min/1.73 m² until age 35-40 years 2, 3
Age-Related Decline
- After age 40: GFR begins to decline linearly at a rate of approximately 6.6-7.7 mL/min/1.73 m²/decade 3
- Females experience faster decline (7.7 mL/min/1.73 m²/decade) compared to males (6.6 mL/min/1.73 m²/decade) after age 35 3
- The mean rate of decline is approximately 0.75 mL/min/year with aging 1
Clinical Thresholds
What Constitutes Normal vs. Abnormal
- GFR ≥90 mL/min/1.73 m² is considered optimal kidney function and is recommended for living kidney donors 1
- GFR 60-89 mL/min/1.73 m² represents mildly decreased kidney function but may be normal for older adults 1, 4
- GFR <60 mL/min/1.73 m² represents loss of half or more of normal adult kidney function and is the threshold for defining chronic kidney disease 1
Important Age Considerations
- In adults over 70 years, GFR values below 60 mL/min/1.73 m² may be considered physiologically normal due to age-related decline 5
- Approximately 17% of persons older than 60 years have an estimated GFR <60 mL/min/1.73 m² 1
- 10.5% of healthy individuals aged >60 years have GFR <60 mL/min/1.73 m² 3
Sex Differences in Normal GFR
- Males consistently have higher GFR than females across all age groups (mean 92.0 vs 88.1 mL/min/1.73 m²) 3
- This sex difference persists throughout the lifespan and is incorporated into GFR estimating equations 2
Critical Clinical Context
When GFR Alone Is Insufficient
- GFR >60 mL/min/1.73 m² does not exclude kidney disease if other markers of kidney damage are present, such as albuminuria (≥30 mg/g creatinine), abnormal urine sediment, or structural abnormalities on imaging 1, 6
- Normal GFR values overlap with CKD stages 1 and 2, making additional testing essential 6
Factors Affecting GFR Accuracy
- Extremes of muscle mass or weight (obesity, amputees, malnutrition) can affect eGFR accuracy 1
- Non-steady state conditions such as acute illness, diabetes with hyperfiltration, or recent surgery may produce inaccurate estimates 1
- Hydration status significantly impacts measurements 1
Common Pitfalls to Avoid
- Do not rely on serum creatinine alone to assess kidney function; always calculate GFR 1
- Do not apply a single GFR threshold across all ages; consider age-appropriate reference ranges 5
- Do not diagnose CKD based solely on a single GFR measurement; chronic kidney disease requires persistent abnormalities for ≥3 months 1
- Do not assume GFR <60 mL/min/1.73 m² always indicates disease in elderly patients without other markers of kidney damage 5