Understanding eGFR and Kidney Function Screening
Glomerular Filtration Rate (GFR) is widely recognized as the single best overall index of kidney function in clinical medicine. It reflects the total volume of blood fluid filtered by the kidney glomeruli per minute, normalized for standard body surface area (1.73 m²).
Because direct measurement of GFR requires invasive continuous IV infusions of exogenous filtration markers (such as iohexol or inulin), clinical practice relies on estimated GFR (eGFR) derived from blood serum creatinine concentrations, biological sex, and age.
The 2021 CKD-EPI Race-Free Equation Standard
In 2021, the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN) Task Force recommended the immediate adoption of the 2021 CKD-EPI creatinine equation across all medical laboratories. This updated clinical standard removes race-based coefficients, providing a standardized, equitable formula for estimating renal function across all patient populations.
Where Scr is serum creatinine (mg/dL), κ is 0.7 for females and 0.9 for males, and α is -0.241 for females and -0.302 for males.
To monitor additional key physical health indicators, calculate your Body Mass Index using our free BMI Calculator or estimate daily hydration recommendations with our Water Intake Calculator.
Chronic Kidney Disease (CKD) Stages Breakdown
| Stage | eGFR Range (mL/min/1.73m²) | Clinical Description |
|---|---|---|
| Stage 1 | ≥ 90 | Normal or high kidney function |
| Stage 2 | 60 – 89 | Mildly decreased kidney function |
| Stage 3a | 45 – 59 | Mild to moderate loss of kidney function |
| Stage 3b | 30 – 44 | Moderate to severe loss of kidney function |
| Stage 4 | 15 – 29 | Severe loss of kidney function |
| Stage 5 | < 15 | Kidney failure (End-Stage Renal Disease) |
Frequently Asked Questions (FAQ)
What is eGFR and why is it important?
Estimated Glomerular Filtration Rate (eGFR) measures how efficiently your kidneys filter metabolic waste products like creatinine from your bloodstream. It is the primary metric used by medical practitioners and nephrologists to diagnose and monitor Chronic Kidney Disease (CKD).
Why does the 2021 CKD-EPI formula not ask for race?
In 2021, the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN) established a joint task force that recommended replacing older equations with the 2021 CKD-EPI creatinine equation. This refactored equation removes race variables to eliminate racial bias while maintaining high diagnostic precision.
What is a normal eGFR level by age?
For young and healthy adults, a normal eGFR is 90 mL/min/1.73m² or higher (Stage 1). Because kidney function naturally declines gradually with age, average eGFR levels decrease over time: ~99 for ages 20–29, ~93 for ages 30–39, ~85 for ages 40–49, ~75 for ages 50–59, and ~60–70 for ages 60+.
How are Chronic Kidney Disease (CKD) stages defined?
CKD is clinically categorized into 5 primary stages based on eGFR in mL/min/1.73m²: Stage 1 (≥90, normal or high), Stage 2 (60–89, mildly decreased), Stage 3a (45–59, mild to moderate loss), Stage 3b (30–44, moderate to severe loss), Stage 4 (15–29, severely decreased), and Stage 5 (<15, kidney failure).