Estimates your Glomerular Filtration Rate (GFR) using the CKD-EPI 2021 creatinine equation.
Male
Female
Non-Black
Black
Note: The Black race coefficient is integrated into the CKD-EPI 2021 equation.
Understanding Glomerular Filtration Rate (GFR)
The Glomerular Filtration Rate (GFR) is a crucial measure of kidney function. It represents the volume of fluid filtered by the glomeruli of the kidneys per unit of time. Essentially, it tells doctors how well your kidneys are removing waste and excess fluid from your blood. A normal GFR varies with age but is typically around 90 mL/min/1.73 m² or higher. A GFR below 60 mL/min/1.73 m² for three months or more is generally considered indicative of chronic kidney disease (CKD).
Why is GFR Important?
Monitoring GFR is vital for:
Detecting kidney disease early, often before symptoms appear.
Assessing the stage of chronic kidney disease (CKD).
Adjusting medication dosages, as kidney function affects drug clearance.
Guiding treatment decisions for kidney-related conditions.
How GFR is Estimated
Directly measuring GFR is complex and often requires specialized tests. Therefore, doctors commonly use estimated GFR (eGFR) calculated from a blood test that measures serum creatinine. Serum creatinine is a waste product generated from normal muscle metabolism. Healthy kidneys filter creatinine efficiently, so higher levels in the blood often suggest reduced kidney function.
The CKD-EPI 2021 Equation
The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation is a widely used and validated method for estimating GFR. The 2021 version is an updated formula that refines eGFR estimation. It incorporates serum creatinine level, age, sex, and race.
Scr is the serum creatinine concentration (mg/dL).
Age is in years.
<slope> and <alpha_coefficient> depend on sex and race.
genderFactor is 1 for males and 0.917 for females.
raceFactor is 1.159 for Black individuals (if applicable to the specific equation version) and 1 otherwise.
Note: The CKD-EPI 2021 equation simplifies the race component and is generally applied universally, with specific coefficients embedded. This calculator uses the standard CKD-EPI 2021 implementation.
The specific values for the slope, alpha coefficient, and factors are adjusted based on the inputs provided (serum creatinine, age, gender, and race). Our calculator uses the latest CKD-EPI 2021 creatinine-based equation to provide the most accurate estimation possible.
Interpreting Your eGFR Result
The eGFR is reported in milliliters per minute per 1.73 square meters of body surface area (mL/min/1.73 m²).
eGFR ≥ 90: May be normal, especially in younger individuals. However, if accompanied by other signs of kidney damage (like protein in the urine), it could indicate early kidney disease.
eGFR 60-89: May indicate mild kidney damage or early CKD, especially if present for more than 3 months or with other indicators of kidney damage.
eGFR 30-59: Indicates moderate kidney damage or moderate CKD.
eGFR 15-29: Indicates severe kidney damage or severe CKD.
eGFR < 15: Indicates kidney failure, requiring dialysis or a kidney transplant.
Disclaimer: This calculator provides an estimated GFR for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.
function calculateGFR() {
var serumCreatinine = parseFloat(document.getElementById("serumCreatinine").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");
resultDiv.style.display = 'block';
resultDiv.className = 'error'; // Reset to error state
// Input validation
if (isNaN(serumCreatinine) || serumCreatinine <= 0) {
resultDiv.innerHTML = "Please enter a valid serum creatinine value (greater than 0).";
return;
}
if (isNaN(age) || age < 1) {
resultDiv.innerHTML = "Please enter a valid age (1 year or older).";
return;
}
var scr = serumCreatinine;
var ageVal = age;
var sexCoefficient;
var raceCoefficient;
// CKD-EPI 2021 Equation coefficients
var slope;
var alpha_coefficient;
if (gender === "male") {
sexCoefficient = 1;
slope = 1.012;
alpha_coefficient = -0.329;
} else { // female
sexCoefficient = 0.917;
slope = 1.012; // slope is same for males and females in 2021 equation based on scr/slope ratio
alpha_coefficient = -0.329; // alpha is same for males and females in 2021 equation
}
if (race === "black") {
raceCoefficient = 1.159; // CKD-EPI 2021 explicitly includes a Black race coefficient
} else {
raceCoefficient = 1;
}
// Ensure coefficients are correct for CKD-EPI 2021
// CKD-EPI 2021 is typically implemented with specific values for 'k' and 'alpha' that vary by sex.
// The 2021 update is more nuanced. For simplicity and common implementation:
// Let's use the standard CKD-EPI 2021 calculation structure.
// The 2021 equation is:
// eGFR = 142 x (serum_creatinine / a)^b x 0.9938^age x [female factor] x [race factor]
// where a and b depend on sex.
var a_val;
var b_val;
if (gender === "male") {
a_val = 0.9;
b_val = -1.279;
} else { // female
a_val = 0.7;
b_val = -1.211;
}
// Apply the Black race factor if selected
var finalRaceFactor = (race === "black") ? 1.159 : 1;
var egfr = 142 * Math.pow((scr / a_val), b_val) * Math.pow(0.9938, ageVal) * sexCoefficient * finalRaceFactor;
// Ensure eGFR is not negative (can happen with very low creatinine, high age, etc.)
egfr = Math.max(0, egfr);
// Round to two decimal places
var formattedEGFR = egfr.toFixed(2);
resultDiv.innerHTML = "Estimated GFR (eGFR): " + formattedEGFR + " mL/min/1.73 m²";
resultDiv.className = "; // Remove error class
}
function resetForm() {
document.getElementById("serumCreatinine").value = "";
document.getElementById("age").value = "";
document.getElementById("gender").value = "male";
document.getElementById("race").value = "non-black";
document.getElementById("result").style.display = 'none';
document.getElementById("result").innerHTML = "";
}
// Update the placeholder text in the formula section dynamically based on selection
function updateRacePlaceholder() {
var raceSelect = document.getElementById("race");
var raceEqPlaceholder = document.getElementById("raceEqPlaceholder");
var genderSelect = document.getElementById("gender");
var genderFactorSpan = document.getElementById("genderFactor");
var raceText = raceSelect.options[raceSelect.selectedIndex].text;
var genderText = genderSelect.options[genderSelect.selectedIndex].text;
raceEqPlaceholder.textContent = raceText + " Race";
// Update the gender factor description in the formula box
if (genderText === "Male") {
genderFactorSpan.textContent = "[Male factor = 1]";
} else {
genderFactorSpan.textContent = "[Female factor = 0.917]";
}
}
// Initialize placeholders and add listeners
document.addEventListener('DOMContentLoaded', function() {
updateRacePlaceholder(); // Initial update
document.getElementById("race").addEventListener("change", updateRacePlaceholder);
document.getElementById("gender").addEventListener("change", updateRacePlaceholder);
});