What is eGFR and why is it important?

Estimated Glomerular Filtration Rate (eGFR) is the best overall index of kidney function. It estimates how well your kidneys filter blood, measured in mL/min/1.73m². Normal eGFR is ≥90. It's used to detect, stage, and monitor chronic kidney disease (CKD).

What is the difference between eGFR and CrCl?

eGFR (CKD-EPI) is used for CKD staging and screening. Creatinine Clearance (CrCl, Cockcroft-Gault) is preferred for drug dosing adjustments. CrCl is not standardized to body surface area and may be more appropriate for extremes of weight.

What is CKD-EPI 2021?

CKD-EPI 2021 is the latest equation recommended by KDIGO for estimating GFR. It's 'race-neutral' (doesn't include race as a variable). It replaced the 2009 CKD-EPI equation and is more accurate across populations.

What factors can affect creatinine and eGFR accuracy?

Factors affecting accuracy: muscle mass (more muscle = higher creatinine), diet (high meat intake), medications (trimethoprim, cimetidine), acute kidney injury (creatinine still rising/falling), age extremes, and malnutrition. Consider cystatin C if these factors are present.

What do the CKD stages mean?

G1 (≥90): Normal or high function. G2 (60-89): Mildly decreased. G3a (45-59): Mild-moderate decrease. G3b (30-44): Moderate-severe decrease. G4 (15-29): Severely decreased. G5 (<15): Kidney failure. Stage G3a+ may require nephrology referral.

When should I refer to nephrology?

Consider nephrology referral for: eGFR 5 mL/min/year), persistent proteinuria (ACR >300), difficult-to-control hypertension, electrolyte abnormalities (hyperkalemia, acidosis), or unknown etiology of CKD.

eGFR Calculator

Q: When should I refer to nephrology?

Consider nephrology referral for: eGFR 5 mL/min/year), persistent proteinuria (ACR >300), difficult-to-control hypertension, electrolyte abnormalities (hyperkalemia, acidosis), or unknown etiology of CKD.

Estimate kidney function using CKD-EPI 2021 equation. Includes CKD staging and Cockcroft-Gault creatinine clearance for drug dosing.

Patient Data

Serum Creatinine

mg/dL

Serum creatinine level from blood test. Normal: 0.7-1.3 mg/dL (male), 0.6-1.1 mg/dL (female). Higher values indicate reduced kidney function.

Age

years

Patient's age in years. eGFR naturally declines with age. The CKD-EPI formula accounts for age-related changes in kidney function.

Weight (for CrCl)

Actual body weight in kilograms. Used for Cockcroft-Gault CrCl calculation. For obese patients, some clinicians use adjusted or ideal body weight.

Note: Sex affects the formula because females typically have less muscle mass and therefore lower baseline creatinine.

CKD-EPI 2021

— mL/min/1.73m²

Enter patient data

CKD Stage

Creatinine Clearance (CrCl)

— mL/min

Cockcroft-Gault • Use for drug dosing

CKD Staging

G3a

G3b

≥90

60-89

45-59

30-44

15-29

<15

The Formulas

CKD-EPI 2021 (eGFR)

142 × min(Cr/κ, 1)^α × max(Cr/κ, 1)^-1.200 × 0.9938^age × 1.012 (if female)

κ = 0.7 (F), 0.9 (M) | α = -0.241 (F), -0.302 (M)

Cockcroft-Gault (CrCl)

CrCl = [(140 - age) × weight] / (72 × Cr) × 0.85 (if female)

= [(140 - 45) × 70] / (72 × 1) = mL/min

Reference: Inker LA, et al. New Creatinine- and Cystatin C–Based Equations. NEJM 2021.

Frequently Asked Questions

How to Use

About the eGFR Calculator

What it calculates

Estimates glomerular filtration rate using the CKD-EPI equation to assess kidney function from creatinine, age, and sex.

When to use it

Use in clinical settings to stage chronic kidney disease and monitor renal function over time.

Example

An eGFR below 60 mL/min/1.73m² for 3+ months may indicate chronic kidney disease.

Explore More

eGFR Calculator

Patient Data

— mL/min/1.73m²

CKD Staging

The Formulas

About the eGFR Calculator

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