eGFR Calculator (CKD-EPI 2021 Formula)
Understanding the eGFR Calculation Formula
The Estimated Glomerular Filtration Rate (eGFR) is the primary test used by healthcare professionals to screen for and monitor kidney disease. It estimates how much blood passes through the glomeruli—the tiny filters in the kidneys—each minute. A higher eGFR generally indicates better kidney function.
The CKD-EPI 2021 Formula
This calculator utilizes the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) 2021 formula. This is the most current, race-neutral standard recommended by the National Kidney Foundation and the American Society of Nephrology. Unlike older versions (like the 2009 CKD-EPI or MDRD), it does not include a coefficient for race, providing a more equitable assessment of kidney health.
How the Math Works
The formula varies slightly based on sex and creatinine levels:
- For Females: eGFR = 142 × min(Scr/0.7, 1)-0.241 × max(Scr/0.7, 1)-1.200 × 0.9938Age × 1.012
- For Males: eGFR = 142 × min(Scr/0.9, 1)-0.302 × max(Scr/0.9, 1)-1.200 × 0.9938Age
CKD Stages Interpretation
Healthcare providers use the following stages to interpret eGFR results:
| Stage | eGFR Range | Description |
|---|---|---|
| Stage 1 | 90 or above | Normal or high function |
| Stage 2 | 60 – 89 | Mildly decreased |
| Stage 3a | 45 – 59 | Mildly to moderately decreased |
| Stage 3b | 30 – 44 | Moderately to severely decreased |
| Stage 4 | 15 – 29 | Severely decreased |
| Stage 5 | Below 15 | Kidney failure (ESRD) |
Realistic Example
Consider a 55-year-old male with a serum creatinine level of 1.2 mg/dL. Applying the CKD-EPI formula, his calculated eGFR would be approximately 73 mL/min/1.73 m². This would place him in Stage 2 (Mildly decreased function), which is common as people age but warrants monitoring.
Medical Disclaimer: This calculator is for educational purposes only and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician regarding clinical decisions.