Glomerular Filtration Rate (eGFR) Calculator

Estimate kidney function using serum creatinine levels. Essential tool for medical professionals in nephrology.

Disclaimer: This tool is for educational purposes only. It does not replace professional medical advice. Clinical decisions should be based on comprehensive assessment by qualified healthcare providers.

CKD-EPI Formula
MDRD Formula
Cockcroft-Gault
Pediatric (Schwartz)
CKD-EPI Formula (2009)

Most accurate for estimating GFR in adults using serum creatinine, age, sex, and race.

Normal range: 0.7-1.3 mg/dL (adults)
Age in years
Adjustment factor applied for Black individuals
kg
Required for Cockcroft-Gault formula
Pediatric GFR Calculation (Schwartz Formula)
Age in years (1-17 years)
Constant varies by age and method
mg/dL
For trend analysis
For calculating rate of change

Formula Comparison: Compare results from different formulas to understand variations.

Calculating...

Understanding Glomerular Filtration Rate (GFR)

The glomerular filtration rate (GFR) is the best overall index of kidney function. It represents the flow rate of filtered fluid through the kidneys. Estimated GFR (eGFR) is calculated from serum creatinine levels and other factors.

Key Concepts:

  • Glomerulus: A network of capillaries in the kidney that filters blood
  • Creatinine: A waste product from muscle metabolism that is filtered by the kidneys
  • eGFR: Estimated GFR calculated using formulas based on serum creatinine
  • CKD Stages: Classification of chronic kidney disease based on eGFR

Chronic Kidney Disease (CKD) Staging

Stage eGFR (mL/min/1.73m²) Description Clinical Management
G1 ≥ 90 Normal or high Monitor, treat underlying conditions
G2 60-89 Mildly decreased Monitor, reduce risk factors
G3a 45-59 Mild to moderate decrease Evaluate and treat complications
G3b 30-44 Moderate to severe decrease Evaluate and treat complications
G4 15-29 Severely decreased Prepare for renal replacement therapy
G5 < 15 Kidney failure Renal replacement therapy

eGFR Calculation Formulas

1

CKD-EPI (2009) Formula: Most accurate formula for estimating GFR, recommended by KDIGO guidelines. More accurate at higher GFR levels than MDRD.

2

MDRD (Modification of Diet in Renal Disease) Formula: Widely used 4-variable formula. Less accurate at higher GFR levels (>60 mL/min/1.73m²).

3

Cockcroft-Gault Formula: Estimates creatinine clearance rather than GFR. Requires weight. Older formula still used for drug dosing.

4

Schwartz Formula (Pediatric): Used for children and adolescents. GFR = k × height(cm) / serum creatinine(mg/dL).

Factors Affecting eGFR Interpretation

1

Muscle Mass: Creatinine production depends on muscle mass. Low muscle mass may overestimate GFR.

2

Dietary Protein: High meat intake can temporarily increase serum creatinine.

3

Medications: Some drugs affect creatinine production or secretion (e.g., trimethoprim, cimetidine).

4

Pregnancy: GFR normally increases during pregnancy by 40-50%.

5

Acute Illness: eGFR formulas are validated for stable outpatients, not acute illness.

Clinical Applications

  • CKD Diagnosis: Identifying and staging chronic kidney disease
  • Drug Dosing: Adjusting medication doses based on kidney function
  • Contrast Risk Assessment: Evaluating risk of contrast-induced nephropathy
  • Transplant Evaluation: Assessing donor and recipient kidney function
  • Prognostic Indicator: Predicting cardiovascular risk and mortality

Clinical Note: eGFR is an estimate and should be interpreted in the context of the patient's clinical condition. Confirmatory tests (24-hour urine collection for creatinine clearance, cystatin C) may be needed in specific situations. Always follow clinical guidelines for diagnosis and management of kidney disease.

Frequently Asked Questions

eGFR is estimated from serum creatinine using formulas and is standardized to body surface area. Creatinine clearance is measured from a 24-hour urine collection and serum creatinine. eGFR is more convenient but creatinine clearance may be more accurate in certain situations (e.g., extremes of muscle mass, amputations).

Studies have shown that Black individuals have, on average, higher muscle mass and higher creatinine generation rates than non-Black individuals with the same kidney function. The race adjustment accounts for this difference. However, this is controversial and newer race-free equations are being developed and validated.

Cystatin C should be considered when creatinine-based eGFR may be inaccurate: in individuals with extremes of muscle mass (bodybuilders, amputees, malnutrition), vegetarian diets, rapidly changing kidney function, or when a more accurate GFR estimate is needed for clinical decisions like chemotherapy dosing.

Frequency depends on CKD stage and risk factors: Stage 1-2 annually; Stage 3 every 6-12 months; Stage 4 every 3-6 months; Stage 5 every 1-3 months. More frequent monitoring may be needed with rapidly changing kidney function, during illness, or when starting nephrotoxic medications.

eGFR formulas assume steady-state creatinine production and elimination. They may be inaccurate in: acute kidney injury, extremes of age and body size, severe malnutrition or obesity, pregnancy, amputees, vegetarians, and those with rapidly changing kidney function. They also don't account for tubular secretion of creatinine.