Normal Glomerular Filtration Rate in Adults
Normal GFR in healthy young adults is approximately 100-130 mL/min/1.73 m² for men and 90-120 mL/min/1.73 m² for women, with values remaining stable until age 40 years, after which physiological decline begins. 1, 2
Age and Sex-Specific Normal Values
Young Adults (Under 40 Years)
- Men: 100-130 mL/min/1.73 m² (some sources cite 120-130 mL/min/1.73 m²) 3, 1, 2
- Women: 90-120 mL/min/1.73 m² 1, 2
- Mean GFR remains approximately 107 mL/min/1.73 m² until age 40 with no significant gender difference in this age range 4
- The older reference value of 120-130 mL/min/1.73 m² appears to overestimate normal GFR based on contemporary measured GFR studies 4, 5
Age-Related Decline After 40 Years
- Physiological decline begins after age 40 years, not from young adulthood as previously thought 1, 2, 4
- Decline rate is 6.6 mL/min/1.73 m²/decade in males 6
- Decline rate is 7.7 mL/min/1.73 m²/decade in females (faster than males) 6
- 10.5% of healthy individuals over 60 years have GFR <60 mL/min/1.73 m², which may represent normal aging rather than disease 6
Clinical Thresholds for Interpretation
Optimal Function
- GFR ≥90 mL/min/1.73 m² is considered optimal kidney function and is the recommended threshold for living kidney donors 1, 2
Mildly Decreased Function
- GFR 60-89 mL/min/1.73 m² represents mildly decreased kidney function but may be normal for older adults, particularly those over 70 years 1, 2
- This range overlaps with early chronic kidney disease stages, so context matters 7
Chronic Kidney Disease Threshold
- GFR <60 mL/min/1.73 m² represents loss of half or more of normal adult kidney function and defines chronic kidney disease 3, 1, 2
- Approximately 17% of persons older than 60 years have estimated GFR <60 mL/min/1.73 m² 3, 1
- This threshold is controversial in elderly patients where lower values may represent normal aging 8, 6
Critical Clinical Context and Pitfalls
When GFR Values Are Misleading
- GFR >60 mL/min/1.73 m² does not exclude kidney disease if other markers are present, such as albuminuria (>30 mg/g creatinine) or structural abnormalities on imaging 1, 2
- Chronic kidney disease requires persistent abnormalities for ≥3 months—never diagnose based on a single GFR measurement 1, 2
Factors Affecting GFR Accuracy
- Extremes of muscle mass or body weight significantly affect estimated GFR accuracy 1, 2
- Non-steady state conditions (acute illness, recent surgery, dehydration) produce inaccurate estimates 1, 2
- Hydration status significantly impacts measurements and must be considered 1, 2
Essential Practice Points
- Never use serum creatinine alone to assess kidney function—always calculate GFR 1, 2
- Always assess both GFR and albuminuria together for comprehensive kidney function evaluation 2
- In elderly patients (>70 years), values of 60-89 mL/min/1.73 m² may represent normal aging rather than pathology, particularly in the absence of proteinuria or other kidney damage markers 1, 2, 8