Estimated Glomerular Filtration Rate Calculation

Calculate your kidney function using the CKD-EPI equation, the most accurate formula for estimating glomerular filtration rate (GFR).

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

Your eGFR provides critical information about:

• Kidney health status – Normal eGFR is 90 or higher. Values below 60 for 3+ months indicate CKD.
• Disease progression – Declining eGFR over time shows worsening kidney function.
• Treatment planning – Helps determine when to start dialysis or consider transplant.
• Medication dosing – Many drugs require adjustment for reduced kidney function.

How eGFR Is Calculated

The most accurate formula is the CKD-EPI equation (2021), which considers:

1. Serum creatinine – A waste product from muscle metabolism
2. Age – Kidney function naturally declines with age
3. Sex – Women typically have lower creatinine levels
4. Race – Historical adjustment for Black individuals (though this is being reconsidered)

CKD Stages Based on eGFR

Stage	eGFR (mL/min/1.73m²)	Description	Actions
1	>90	Normal kidney function	Maintain healthy lifestyle
2	60-89	Mildly reduced function	Monitor, control risk factors
3a	45-59	Mild to moderate reduction	Evaluate for CKD causes
3b	30-44	Moderate to severe reduction	Prepare for possible progression
4	15-29	Severe reduction	Plan for kidney replacement
5	<15	Kidney failure	Dialysis or transplant needed

Factors Affecting eGFR Accuracy

While eGFR is highly useful, certain conditions can affect its accuracy:

• Extreme body size – Very muscular or obese individuals may get inaccurate results
• Rapidly changing kidney function – Acute kidney injury requires different assessment
• Pregnancy – GFR naturally increases during pregnancy
• Diet – High protein intake can temporarily increase creatinine
• Medications – Some drugs affect creatinine levels

eGFR vs. Creatinine Clearance

While related, these measure different things:

eGFR vs Creatinine Clearance Comparison

Feature	eGFR	Creatinine Clearance
What it measures	Estimated filtration rate	Actual creatinine clearance
Method	Calculated from blood test	24-hour urine collection
Accuracy	Good for screening	More precise but inconvenient
Use in practice	Standard for CKD evaluation	Used for drug dosing
Cost	Low (single blood test)	Higher (multiple collections)

Improving Your eGFR

While you can’t reverse kidney damage, you can slow progression:

1. Control blood pressure – Target <130/80 mmHg (or <120/80 with proteinuria)
2. Manage blood sugar – HbA1c <7% for diabetics
3. Healthy diet – DASH diet, lower salt, adequate protein
4. Exercise regularly – 150+ minutes weekly of moderate activity
5. Avoid NSAIDs – Ibuprofen, naproxen can harm kidneys
6. Stay hydrated – Unless fluid-restricted
7. Quit smoking – Smoking damages kidney blood vessels
8. Limit alcohol – No more than 1 drink/day for women, 2 for men

When to See a Doctor

Consult a nephrologist (kidney specialist) if you have:

• eGFR <60 for 3+ months
• eGFR declining by >5 mL/min/year
• Protein in urine (albuminuria)
• Blood in urine (hematuria)
• Symptoms like swelling, fatigue, or frequent urination
• Family history of kidney disease
• Diabetes or high blood pressure

Authoritative Resources on eGFR

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) – GFR Information

National Kidney Foundation – Professional GFR Calculator

Cornell University – CKD-EPI GFR Calculator with Research