What are normal Glomerular Filtration Rate (GFR) values?

Normal GFR Values

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 values remaining stable until around age 40 years before beginning a physiological decline. 1

Age-Specific Normal Values

Young Adults (Under 40 Years)

• Men: Approximately 120-130 mL/min/1.73 m² 1
• Women: Approximately 90-120 mL/min/1.73 m² 1
• More recent evidence suggests the mean GFR is closer to 107 mL/min/1.73 m² for both sexes, remaining constant until age 40 2

Middle-Aged and Older Adults

• GFR remains stable at approximately 107 mL/min/1.73 m² until age 40, then begins to decline 2
• The physiological decline averages 0.75 mL/min per year after age 40 1
• In adults over 70 years, values below 60 mL/min/1.73 m² may be considered within the normal age-adjusted range 3

Clinical Context and Interpretation

What Constitutes "Normal" vs. Disease

• GFR ≥90 mL/min/1.73 m² is classified as CKD Stage G1 (normal or high) but only represents CKD if kidney damage markers are present 1
• GFR 60-89 mL/min/1.73 m² is classified as CKD Stage G2 (mildly decreased) but again requires evidence of kidney damage to diagnose CKD 1
• GFR <60 mL/min/1.73 m² represents loss of half or more of normal adult kidney function and marks the threshold where CKD complications increase 1

Important Caveats for Kidney Donor Evaluation

• For living kidney donor candidates, a GFR ≥90 mL/min/1.73 m² is recommended as the minimum threshold 1
• Candidates with GFR 60-89 mL/min/1.73 m² require individualized risk assessment, though GFR 60-70 mL/min/1.73 m² in younger donors (e.g., age 25) would be unusually low and concerning 1
• GFR <60 mL/min/1.73 m² should exclude donation 1

Measurement Considerations

Accuracy of Estimation Methods

• Serum creatinine alone is insufficient for accurate GFR assessment 1
• Estimated GFR (eGFR) using equations like CKD-EPI or MDRD is acceptable for screening, but confirmatory testing with measured GFR using exogenous filtration markers (iothalamate, iohexol) is preferred when precision is required 1
• eGFR equations can be inaccurate in extremes of muscle mass, obesity, amputees, or non-steady-state conditions like acute illness 1
• Measured creatinine clearance typically overestimates GFR by 10-20% due to tubular secretion 1

Reference Ranges from Research Studies

• Healthy adult reference intervals for eGFR range from 63.5-139.2 mL/min/1.73 m² depending on the equation used 4
• In healthy potential kidney donors, 97.2% had measured GFR values within age-dependent reference limits 5

Key Clinical Pitfalls to Avoid

• Do not rely on serum creatinine alone to assess kidney function, as it can remain within normal range until GFR drops below 60 mL/min/1.73 m² 1
• Do not ignore age when interpreting GFR values—a GFR of 70 mL/min/1.73 m² may be normal for a 70-year-old but abnormal for a 25-year-old 1, 3
• Do not diagnose CKD based solely on GFR without evidence of kidney damage (proteinuria, abnormal imaging, etc.) if GFR is ≥60 mL/min/1.73 m² 1
• Do not assume GFR decline with aging is benign—even age-related GFR reduction is an independent predictor of adverse outcomes including death and cardiovascular disease 1