eGFR Kidney Function Calculator
Estimate your glomerular filtration rate (eGFR) using the official 2021 CKD-EPI creatinine equation to screen for and stage chronic kidney disease (CKD).
KDIGO CKD Staging
What Is a eGFR Kidney Function Calculator?
A eGFR Kidney Function Calculator is a renal health calculation tool developed to estimate kidney filtration efficiency and clearance capacity. It utilizes validated clinical equations, such as the CKD-EPI 2021 formula or the Cockcroft-Gault equation, using parameters like serum creatinine, age, and biological sex. These estimates assist in understanding kidney filtration staging for educational purposes and should always be confirmed through comprehensive nephrology evaluation.
How to Use This Calculator
- Enter your serum creatinine level in mg/dL (or $\mu\text{mol/L}$).
- Select your biological sex.
- Input your current age in years and click 'Calculate eGFR'.
How This Calculator Works
The tool applies the 2021 CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) refitted equation without race coefficients: $\text{eGFR} = 142 \times \min(\text{Scr}/\kappa, 1)^\alpha \times \max(\text{Scr}/\kappa, 1)^{-1.200} \times 0.9938^\text{Age} \times [1.012\text{ if female}]$, where $\kappa = 0.7$ (females) or $0.9$ (males), and $\alpha = -0.241$ (females) or $-0.302$ (males).
Understanding Your Results
An eGFR of 90 or higher reflects normal or high kidney filtration (Stage 1 if structural damage exists). An eGFR of 60-89 represents mildly decreased filtration (Stage 2). An eGFR persistently below 60 mL/min/1.73m² for >3 months indicates Chronic Kidney Disease (Stages 3-5). An eGFR below 15 reflects kidney failure.
Frequently Asked Questions
Why is eGFR labeled an 'estimate'?
Directly measuring GFR requires infusing exogenous filtration markers (such as inulin or iohexol). eGFR estimates this filtration rate using endogenous serum creatinine, which is influenced by muscle mass and dietary protein.
Can bodybuilders have a falsely low eGFR?
Yes. Individuals with substantial muscular hypertrophy or those who supplement with creatine monohydrate generate higher baseline creatinine, which can artificially lower creatinine-based eGFR. In such cases, measuring serum Cystatin C provides an unbiased, accurate GFR estimate.
What symptoms signal declining kidney function?
Early CKD is typically asymptomatic ('silent'). Advanced stages can manifest with fluid retention (edema in ankles/legs), fatigue, foamy urine, decreased appetite, and uncontrolled hypertension.
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Important Limitations & Medical Disclaimer
Notice: eGFR values are mathematical estimates. A formal clinical diagnosis of Chronic Kidney Disease requires comprehensive urine albumin-to-creatinine ratio (uACR) testing, renal ultrasound imaging, and clinical physician evaluation.