eGFR Calculator
Estimate glomerular filtration rate using the CKD-EPI formula
Your eGFR Results
Comprehensive Guide to Estimated Glomerular Filtration Rate (eGFR) Calculation
The estimated glomerular filtration rate (eGFR) is the best overall measure of kidney function. It estimates how much blood passes through the glomeruli (tiny filters in the kidneys) each minute. Healthcare providers use eGFR to screen for, detect, and monitor chronic kidney disease (CKD).
Why eGFR Matters in Kidney Health
Your eGFR provides critical information about:
- How well your kidneys are filtering waste from your blood
- Whether you have kidney damage or disease
- The stage of chronic kidney disease (if present)
- Your risk for kidney failure and cardiovascular complications
The CKD-EPI Formula: The Gold Standard
The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is currently the most accurate formula for estimating GFR. It was developed in 2009 and is recommended by the National Kidney Foundation and National Institute of Diabetes and Digestive and Kidney Diseases.
The CKD-EPI formula considers:
- Serum creatinine level (mg/dL)
- Age (years)
- Sex (male or female)
- Race (Black or non-Black)
| Variable | Impact on eGFR |
|---|---|
| Higher creatinine | Lower eGFR (worse kidney function) |
| Older age | Lower eGFR (normal age-related decline) |
| Female sex | Slightly lower eGFR (normal physiological difference) |
| Black race | Higher eGFR (accounting for higher average muscle mass) |
Understanding Your eGFR Results
eGFR results are categorized into stages of chronic kidney disease:
| CKD Stage | eGFR (mL/min/1.73m²) | Description | Prevalence in U.S. Adults |
|---|---|---|---|
| 1 | >90 | Normal or high kidney function | ~37% |
| 2 | 60-89 | Mildly decreased kidney function | ~30% |
| 3a | 45-59 | Mild to moderate decrease | ~11% |
| 3b | 30-44 | Moderate to severe decrease | ~4% |
| 4 | 15-29 | Severe decrease | ~0.6% |
| 5 | <15 | Kidney failure (dialysis needed) | ~0.15% |
Source: CDC Chronic Kidney Disease Surveillance System
Limitations of eGFR Calculations
While eGFR is extremely valuable, it has some limitations:
- Muscle mass effects: Creatinine comes from muscle breakdown, so people with very high or low muscle mass may get inaccurate results
- Acute changes: eGFR doesn’t reflect sudden changes in kidney function (use actual GFR measurement for acute kidney injury)
- Extreme values: The formula is less accurate at very high (>120 mL/min) or very low (<15 mL/min) GFR levels
- Race adjustment: The race coefficient is controversial and may be removed from future equations
When to See a Nephrologist
Consult a kidney specialist if you have:
- eGFR < 30 mL/min/1.73m² (Stage 4 or 5 CKD)
- Rapidly declining eGFR (>5 mL/min/year)
- eGFR < 60 with protein in urine (albuminuria)
- Symptoms like swelling, fatigue, or frequent urination
- Family history of kidney disease or dialysis
Improving Your Kidney Function
While you can’t reverse chronic kidney damage, you can slow progression with:
- Blood pressure control: Target <130/80 mmHg (or <120/80 with proteinuria)
- Blood sugar management: HbA1c <7% for diabetics
- Healthy diet: DASH diet, low sodium (<2300 mg/day), controlled protein
- Regular exercise: 150+ minutes of moderate activity weekly
- Avoiding NSAIDs: Ibuprofen, naproxen can worsen kidney function
- Smoking cessation: Smoking accelerates kidney damage
- Weight management: BMI 18.5-24.9 reduces kidney stress
Emerging Research in GFR Estimation
Scientists are developing more accurate GFR estimation methods:
- Cystatin C: A protein not affected by muscle mass that may improve accuracy
- Combined equations: Using both creatinine and cystatin C
- Race-neutral equations: New formulas without race coefficients
- AI models: Machine learning algorithms incorporating more variables
For the most current clinical guidelines, refer to the Kidney Disease: Improving Global Outcomes (KDIGO) organization.