Estimate your Glomerular Filtration Rate (eGFR) using standard formulas. Please consult a healthcare professional for accurate diagnosis and treatment.
Male
Female
White
Black or African American
Asian
Other/Unknown
Estimated GFR (eGFR)
—
mL/min/1.73 m²
This is an estimated value. Consult your doctor for medical advice.
Understanding Glomerular Filtration Rate (GFR)
Glomerular Filtration Rate (GFR) is a crucial indicator of kidney function. It measures how effectively your kidneys filter waste products and excess fluid from your blood. The kidneys contain millions of tiny filtering units called glomeruli. GFR estimates the volume of fluid that is filtered by these glomeruli per unit of time.
Why is GFR Important?
Early Detection of Kidney Disease: A declining GFR is often one of the first signs of chronic kidney disease (CKD).
Monitoring Disease Progression: Tracking GFR helps healthcare providers understand how quickly kidney function is worsening.
Treatment Decisions: GFR levels inform treatment plans, medication dosages, and decisions about dialysis or transplantation.
How is GFR Calculated?
Directly measuring GFR is complex and typically done in a clinical setting with specialized tests. However, healthcare professionals commonly use formulas to estimate GFR (eGFR) based on simple blood tests and demographic information. The most widely used formulas are the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation and the MDRD (Modification of Diet in Renal Disease) study equation. This calculator utilizes the CKD-EPI 2021 equation, which is considered more accurate across a wider range of GFR values, especially for individuals with higher kidney function.
The CKD-EPI 2021 Equation
The CKD-EPI 2021 equation is a complex formula that incorporates serum creatinine, age, sex, and race. For black individuals, an additional factor is applied. The equation is presented in different forms depending on the serum creatinine level.
Note: The CKD-EPI 2021 equation has been updated and simplified, generally removing the explicit race coefficient for most populations. However, for historical context and some specific clinical guidelines, race may still be considered. This calculator includes it as an option based on older versions of the equation.
Interpreting Your eGFR Results
Normal GFR: Typically 90 mL/min/1.73 m² or higher.
Mildly decreased GFR (but kidney damage possible): 60-89 mL/min/1.73 m² for 3 months or more may indicate CKD.
Moderately decreased GFR: 30-59 mL/min/1.73 m².
Severely decreased GFR: 15-29 mL/min/1.73 m².
Kidney Failure: Less than 15 mL/min/1.73 m².
It's important to note that GFR naturally declines with age. However, a significant drop or consistently low GFR can signal kidney disease. This calculator provides an estimate; always discuss your results with a healthcare provider.
Factors Influencing eGFR Calculation
Serum Creatinine: A waste product from muscle metabolism. Higher levels generally indicate poorer kidney function.
Age: GFR tends to decrease gradually as people age.
Gender: Men typically have slightly higher muscle mass, leading to higher creatinine levels and adjustments in the formula.
Race: Historically, formulas included a race coefficient due to observed differences in muscle mass and creatinine production. However, the use of race in eGFR equations is increasingly debated and being phased out in favor of more accurate, race-neutral equations.
BUN (Blood Urea Nitrogen): While not directly used in the CKD-EPI formula, BUN is another indicator of kidney function and can be considered alongside GFR.
function calculateGFR() {
var age = parseFloat(document.getElementById("age").value);
var gender = document.getElementById("gender").value;
var serumCreatinine = parseFloat(document.getElementById("serumCreatinine").value);
var bun = parseFloat(document.getElementById("bun").value); // BUN is not used in CKD-EPI but kept for completeness if future formulas are added
var race = document.getElementById("race").value;
var gfr = 0;
var gfrValueElement = document.getElementById("gfrValue");
var disclaimerElement = document.getElementById("disclaimer");
// Input validation
if (isNaN(age) || isNaN(serumCreatinine) || age < 0 || serumCreatinine < 0) {
gfrValueElement.textContent = "Invalid Input";
gfrValueElement.style.color = "red";
disclaimerElement.textContent = "Please enter valid positive numbers for age and serum creatinine.";
return;
}
var ageFactor = Math.pow(0.996, age);
var creatinineRatio = serumCreatinine / 0.7; // Base ratio for women
var exponent = -1.198;
var constant = 166;
var sexAdjustment = 0.969;
if (gender === "male") {
creatinineRatio = serumCreatinine / 0.9; // Base ratio for men
exponent = -1.200;
constant = 133;
sexAdjustment = 1; // No adjustment for males
}
// CKD-EPI 2021 – simplified structure
if (serumCreatinine <= (gender === "male" ? 0.9 : 0.7)) {
exponent = -0.332;
}
gfr = constant * Math.pow(creatinineRatio, exponent) * ageFactor * sexAdjustment;
// Optional: Adjust for race if using older interpretations or specific guidelines (CKD-EPI 2021 generally removes this)
// The 2021 CKD-EPI is race-neutral, but older versions used race.
// We'll simulate a simplified adjustment for demonstration if 'black' is selected,
// though modern practice moves away from this.
if (race === "black" && gender === "male") {
// For demonstration, simulating a common adjustment factor from older equations
// In reality, CKD-EPI 2021 doesn't use race.
if (serumCreatinine <= 0.9) {
gfr = 133 * Math.pow(creatinineRatio, -0.332) * Math.pow(0.996, age) * 1.212;
} else {
gfr = 133 * Math.pow(creatinineRatio, -1.200) * Math.pow(0.996, age) * 1.212;
}
} else if (race === "black" && gender === "female") {
if (serumCreatinine <= 0.7) {
gfr = 166 * Math.pow(creatinineRatio, -0.332) * Math.pow(0.996, age) * 0.969 * 1.157;
} else {
gfr = 166 * Math.pow(creatinineRatio, -1.198) * Math.pow(0.996, age) * 0.969 * 1.157;
}
}
// Ensure GFR is not negative and set to a minimum reasonable value if calculated very low.
if (gfr 200) gfr = 200; // Arbitrary cap for display
gfrValueElement.textContent = gfr.toFixed(2); // Display with 2 decimal places
gfrValueElement.style.color = "#28a745"; // Success green for positive result
disclaimerElement.textContent = "This is an estimated value. Consult your doctor for medical advice.";
}