Estimate your Glomerular Filtration Rate (GFR) using the CKD-EPI creatinine equation (2021).
Male
Female
Black or African American
Not Black or African American
Estimated GFR
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mL/min/1.73m²
Understanding Glomerular Filtration Rate (GFR)
Glomerular Filtration Rate (GFR) is a crucial test that checks how well your kidneys are filtering waste from your blood. It measures the rate at which fluid is filtered from the glomerular capillaries into the Bowman's capsule. A normal GFR is typically above 90 mL/min/1.73m². As kidney disease progresses, GFR declines.
Why is GFR Important?
Regular monitoring of GFR is essential for early detection and management of Chronic Kidney Disease (CKD). Kidney damage can often occur silently, without noticeable symptoms until significant loss of kidney function has taken place. A GFR test helps healthcare providers:
Detect kidney disease in its early stages.
Determine the stage of kidney disease.
Monitor the progression of kidney disease.
Adjust medication dosages, as kidneys play a vital role in drug metabolism and excretion.
The CKD-EPI Creatinine Equation (2021)
The CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation is a widely used formula to estimate GFR based on serum creatinine levels. The 2021 version is an update that refines the estimation. The general form of the equation for estimating GFR using serum creatinine (SCr) is:
eGFR = 142 × (SCr/κ)α × 0.9938Age × (if female then 0.742 else 1) × (if Black then 1.16 else 1)
Where:
eGFR is the estimated Glomerular Filtration Rate in mL/min/1.73m².
SCr is the serum creatinine level in mg/dL.
Age is the age in years.
κ (kappa) and α (alpha) are constants that depend on sex and race.
For the 2021 CKD-EPI equation, the specific values for κ and α are incorporated within the calculation logic. This calculator implements the updated 2021 coefficients.
Note: The calculator uses simplified coefficients for demonstration purposes, aligning with common implementations. For precise clinical use, refer to the official CKD-EPI 2021 publication.
Interpreting Your GFR Results
Your GFR result helps categorize your kidney function into stages:
Stage 1: GFR 90 or higher with kidney damage (e.g., protein in urine).
Stage 2: GFR 60–89 with kidney damage.
Stage 3a: GFR 45–59.
Stage 3b: GFR 30–44.
Stage 4: GFR 15–29.
Stage 5: GFR less than 15 (kidney failure).
This calculator provides an estimate. Always discuss your GFR results with your healthcare provider for an accurate diagnosis and personalized treatment plan. Factors like diet, hydration, and certain medications can influence creatinine levels and, consequently, GFR estimates.
function calculateGFR() {
var creatinine = parseFloat(document.getElementById("creatinine").value);
var age = parseFloat(document.getElementById("age").value);
var genderFactor = parseFloat(document.getElementById("gender").value);
var raceFactor = parseFloat(document.getElementById("race").value);
var gfrResult = 0;
// Check if inputs are valid numbers
if (isNaN(creatinine) || isNaN(age) || isNaN(genderFactor) || isNaN(raceFactor)) {
document.getElementById("gfrResult").textContent = "Invalid Input";
document.getElementById("stageInfo").textContent = "";
return;
}
// CKD-EPI 2021 Creatinine Equation Coefficients
// These coefficients are simplified for common implementation.
// For precise clinical accuracy, consult the original publication.
var alpha, kappa;
if (raceFactor === 1.16) { // Not Black or African American
alpha = -0.207;
kappa = 0.9;
} else { // Black or African American
alpha = -0.207;
kappa = 1.213;
}
var equationValue = Math.pow(creatinine / kappa, alpha) * Math.pow(0.9938, age) * genderFactor * raceFactor;
if (creatinine / kappa < 0.2) { // If SCr/kappa < 0.2, use a different formula
if (raceFactor === 1.16) { // Not Black or African American
alpha = -0.302;
kappa = 0.81;
} else { // Black or African American
alpha = -0.302;
kappa = 0.99;
}
equationValue = Math.pow(creatinine / kappa, alpha) * Math.pow(0.9938, age) * genderFactor * raceFactor;
}
gfrResult = 142 * equationValue;
// Ensure GFR is not negative
if (gfrResult = 90) {
stageInfo = "Stage 1 or 2 (possible kidney damage, but GFR is normal or near-normal)";
} else if (gfrResult >= 60) {
stageInfo = "Stage 2 (mildly reduced GFR)";
} else if (gfrResult >= 45) {
stageInfo = "Stage 3a (mild to moderately reduced GFR)";
} else if (gfrResult >= 30) {
stageInfo = "Stage 3b (moderately to severely reduced GFR)";
} else if (gfrResult >= 15) {
stageInfo = "Stage 4 (severely reduced GFR)";
} else {
stageInfo = "Stage 5 (kidney failure)";
}
document.getElementById("gfrResult").textContent = gfrResult;
document.getElementById("stageInfo").textContent = stageInfo;
}