Normal Glomerular Filtration Rate (GFR)
Normal GFR in young adults is approximately 120-130 mL/min/1.73 m² in men and 90-120 mL/min/1.73 m² in women, with values remaining stable until age 40, after which physiological decline begins. 1, 2
Age-Specific Normal Values
Young Adults (Under 40 Years)
- Men: 120-130 mL/min/1.73 m² 1
- Women: 90-120 mL/min/1.73 m² 2
- Mean GFR remains approximately 100-107 mL/min/1.73 m² until age 40 2, 3
Middle-Aged and Older Adults (Over 40 Years)
- GFR begins declining after age 40 at approximately 6.6-7.7 mL/min/decade 3, 4
- The decline is faster in females (7.7 mL/min/1.73 m²/decade) compared to males (6.6 mL/min/1.73 m²/decade) 4
- 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 a GFR <60 mL/min/1.73 m² 4
Clinical Thresholds for Kidney Function
Optimal Function
- GFR ≥90 mL/min/1.73 m²: Considered optimal kidney function and recommended for living kidney donors 2
Mildly Decreased Function
- GFR 60-89 mL/min/1.73 m²: Represents mildly decreased kidney function but may be normal for older adults 2
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 1, 2
- This threshold applies regardless of age, though the prevalence increases significantly in elderly populations 1
Critical Clinical Caveats
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 (albumin-creatinine ratio >30 mg/g) or structural abnormalities on imaging 1, 2
- Chronic kidney disease requires persistent abnormalities for ≥3 months; diagnosis should not be based on a single GFR measurement 2
Factors Affecting GFR Accuracy
- Extremes of muscle mass or weight can affect eGFR accuracy 2
- Non-steady state conditions such as acute illness or recent surgery may produce inaccurate estimates 2
- Hydration status significantly impacts measurements 2
- Serum creatinine alone should never be used to assess kidney function; always calculate GFR 2
Age-Related Considerations
- While age-related GFR decline has been considered part of normal aging, decreased GFR in the elderly remains an independent predictor of adverse outcomes including death and cardiovascular disease 1
- The definition of chronic kidney disease remains the same regardless of age, though interpretation must account for physiological decline 1