The Estimated Glomerular Filtration Rate (eGFR) is a key indicator of renal function. By analyzing serum creatinine levels alongside age and gender, medical professionals can estimate how well your kidneys are filtering waste from your blood. This calculator uses the CKD-EPI 2021 equation, which is currently recommended by the National Kidney Foundation.
Female
Male
Typical range: 0.6 to 1.3 mg/dL
Estimated GFR
—
mL/min/1.73m²
function calculateEGFR() {
// Get inputs
var gender = document.getElementById('gender').value;
var ageStr = document.getElementById('age').value;
var creatStr = document.getElementById('creatinine').value;
// Validation
if (ageStr === " || creatStr === ") {
alert("Please enter both Age and Serum Creatinine values.");
return;
}
var age = parseFloat(ageStr);
var scr = parseFloat(creatStr);
if (isNaN(age) || age < 0 || isNaN(scr) || scr = 90) {
stageText = "Stage 1";
stageClass = "stage-1";
desc = "Normal or high kidney function.";
} else if (egfr >= 60) {
stageText = "Stage 2";
stageClass = "stage-2";
desc = "Mildly decreased kidney function.";
} else if (egfr >= 45) {
stageText = "Stage 3a";
stageClass = "stage-3a";
desc = "Mild to moderately decreased kidney function.";
} else if (egfr >= 30) {
stageText = "Stage 3b";
stageClass = "stage-3b";
desc = "Moderate to severely decreased kidney function.";
} else if (egfr >= 15) {
stageText = "Stage 4";
stageClass = "stage-4";
desc = "Severely decreased kidney function.";
} else {
stageText = "Stage 5";
stageClass = "stage-5";
desc = "Kidney failure.";
}
// Update DOM
document.getElementById('egfrResult').innerText = egfr;
document.getElementById('interpretation').innerHTML =
'Interpretation:' + stageText + '' + desc;
document.getElementById('resultBox').style.display = 'block';
}
Understanding the Creatinine and eGFR Blood Test
The eGFR test is generally considered the best way to check kidney function. It is calculated rather than measured directly, using the level of creatinine in your blood. Creatinine is a waste product generated by the normal wear and tear on muscles of the body. Healthy kidneys filter creatinine out of the blood and into the urine to leave the body.
When kidney function slows down, creatinine levels rise. However, relying solely on creatinine levels can be misleading because the amount of creatinine in the blood is also affected by muscle mass. For example, a young bodybuilder will have higher creatinine than an elderly person, even if their kidney function is identical. The eGFR formula corrects for this by incorporating age and gender.
How is eGFR Calculated?
This calculator utilizes the CKD-EPI 2021 Creatinine Equation. This formula is the modern standard recommended by the National Kidney Foundation and the American Society of Nephrology. It replaced older equations (like MDRD and CKD-EPI 2009) to provide more accurate estimates without relying on race as a variable.
The formula variables include:
Serum Creatinine (Scr): Measured in mg/dL.
Age: Kidney function naturally declines slightly with age.
Gender: Used to approximate muscle mass differences between biological males and females.
Interpreting CKD Stages
Chronic Kidney Disease (CKD) is classified into five stages based on the eGFR value. The lower the eGFR, the more reduced the kidney function.
Stage
eGFR Range
Description
Stage 1
90 or higher
Normal kidney function (if other signs of kidney damage are present).
Stage 2
60 – 89
Mild loss of kidney function.
Stage 3a
45 – 59
Mild to moderate loss of kidney function.
Stage 3b
30 – 44
Moderate to severe loss of kidney function.
Stage 4
15 – 29
Severe loss of kidney function. Preparation for dialysis usually begins.
Stage 5
Less than 15
Kidney failure (End Stage Renal Disease). Dialysis or transplant is necessary.
When to Consult a Doctor
An eGFR below 60 for three months or more is a strong indicator of chronic kidney disease. However, a single test result showing low eGFR or high creatinine is not a diagnosis. Dehydration, certain medications, and intense exercise can temporarily affect creatinine levels. Always consult a healthcare professional for a comprehensive evaluation and proper diagnosis.