Estimate your kidney function using the CKD-EPI creatinine (2021) equation.
Male
Female
African American
Non-African American
Your estimated GFR will appear here.
Understanding Glomerular Filtration Rate (GFR)
The Glomerular Filtration Rate (GFR) is a key indicator of kidney function. It measures how much blood passes through the glomeruli each minute. Glomeruli are tiny filters in your kidneys that remove waste and excess fluid from your blood.
A declining GFR can signify kidney disease. Regular monitoring of GFR is crucial for early detection and management of kidney problems, allowing for timely interventions to preserve kidney function.
The CKD-EPI Creatinine (2021) Equation
This calculator uses the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation from 2021, which is widely recommended for estimating GFR. The formula takes into account serum creatinine levels, age, sex, and race.
Mathematical Formula:
The CKD-EPI 2021 equation is complex and involves different calculations based on the interaction of the variables. It is structured in a way that accounts for sex-specific differences in creatinine production and muscle mass. A simplified representation is:
GFR = 141 x min(SCr/κ, 1)^α x max(1 - 0.0009 x age, 0.993)^β x (1.018 if female) x (1.159 if Black)
Where:
SCr is serum creatinine in mg/dL.
κ (kappa) and α (alpha) depend on sex and race:
For males of non-African American race: κ = 0.9, α = -0.302
For females of non-African American race: κ = 0.7, α = -0.241
For males of African American race: κ = 0.9, α = -0.302
For females of African American race: κ = 0.7, α = -0.241
β (beta) is -0.048.
min(SCr/κ, 1) means if SCr/κ is greater than 1, use 1. Otherwise, use SCr/κ.
max(1 - 0.0009 x age, 0.993) means if 1 – 0.0009 x age is less than 0.993, use 0.993. Otherwise, use 1 – 0.0009 x age.
A multiplier of 1.018 is applied for females.
A multiplier of 1.159 is applied for individuals identified as Black.
Important Note: This calculator provides an *estimate* of GFR. It is not a substitute for professional medical advice. Always consult with your healthcare provider for an accurate diagnosis and treatment plan. Factors not included in this equation, such as muscle mass, diet, and certain medications, can also affect creatinine levels.
function calculateGFR() {
var creatinine = parseFloat(document.getElementById("creatinine").value);
var age = parseFloat(document.getElementById("age").value);
var gender = document.getElementById("gender").value;
var race = document.getElementById("race").value;
var resultDiv = document.getElementById("result");
// Input validation
if (isNaN(creatinine) || creatinine <= 0) {
resultDiv.innerHTML = "Please enter a valid serum creatinine value (greater than 0).";
return;
}
if (isNaN(age) || age <= 0) {
resultDiv.innerHTML = "Please enter a valid age (greater than 0).";
return;
}
var kappa, alpha, sexFactor, raceFactor;
// Set parameters based on gender and race
if (gender === "male") {
sexFactor = 1.0;
if (race === "african american") {
kappa = 0.9;
alpha = -0.302;
raceFactor = 1.159;
} else { // non-african american male
kappa = 0.9;
alpha = -0.302;
raceFactor = 1.0;
}
} else { // female
sexFactor = 1.018;
if (race === "african american") {
kappa = 0.7;
alpha = -0.241;
raceFactor = 1.159;
} else { // non-african american female
kappa = 0.7;
alpha = -0.241;
raceFactor = 1.0;
}
}
var creatinineRatio = creatinine / kappa;
var ageFactor = Math.pow(Math.max(1 – 0.0009 * age, 0.993), -0.048);
var creatinineFactor = Math.pow(Math.min(creatinineRatio, 1), alpha);
var gfr = 141 * creatinineFactor * ageFactor * sexFactor * raceFactor;
// Ensure GFR is not negative (though unlikely with these formulas if inputs are valid)
if (gfr < 0) {
gfr = 0;
}
resultDiv.innerHTML = "Estimated GFR: " + gfr.toFixed(2) + " mL/min/1.73m²";
}