Glomerular Filtration Rate (GFR) is widely considered the best overall index of kidney function. It estimates how much blood passes through the glomeruli (tiny filters in the kidneys) each minute. This calculator uses the CKD-EPI equation, which uses your serum creatinine level, age, gender, and race to estimate kidney function.
Chronic Kidney Disease (CKD) Stages
GFR results are typically categorized into five stages of kidney disease. A higher number generally indicates better kidney function.
Stage
GFR Range
Description
Stage 1
90+
Normal or high kidney function (if other signs of kidney damage are present)
Stage 2
60-89
Mildly decreased kidney function
Stage 3a
45-59
Mild to moderately decreased kidney function
Stage 3b
30-44
Moderate to severely decreased kidney function
Stage 4
15-29
Severely decreased kidney function
Stage 5
Below 15
Kidney failure (End Stage Renal Disease)
Important Factors Affecting Creatinine
Creatinine is a waste product from the normal breakdown of muscle tissue. Because it is produced at a relatively constant rate and filtered out by the kidneys, it is a reliable marker for kidney function. However, certain factors can influence levels:
Muscle Mass: Body builders may have naturally higher creatinine, leading to an underestimation of GFR. Conversely, elderly individuals with low muscle mass may have deceptively low creatinine.
Diet: High protein diets or creatine supplements can temporarily raise serum creatinine levels.
Medications: Certain drugs can interfere with creatinine secretion.
Disclaimer: This calculator is for educational purposes only and does not constitute medical advice. Always consult with a healthcare professional for diagnosis and treatment.
function calculateGFR() {
// 1. Get Inputs
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;
// 2. Validate Inputs
if (isNaN(creatinine) || isNaN(age)) {
alert("Please enter valid numbers for Creatinine and Age.");
return;
}
if (age = 90) {
stageText = "Stage 1 (Normal/High)";
stageClass = "stage-normal";
interpText = "Kidney function is normal. Note: Stage 1 CKD is only diagnosed if there is other evidence of kidney damage (like protein in urine).";
} else if (gfr >= 60) {
stageText = "Stage 2 (Mild)";
stageClass = "stage-mild";
interpText = "Mild loss of kidney function. Like Stage 1, this is only considered CKD if other signs of kidney damage are present.";
} else if (gfr >= 45) {
stageText = "Stage 3a (Mild to Moderate)";
stageClass = "stage-moderate";
interpText = "Mild to moderate loss of kidney function. You should be monitored by a doctor.";
} else if (gfr >= 30) {
stageText = "Stage 3b (Moderate to Severe)";
stageClass = "stage-moderate";
interpText = "Moderate to severe loss of kidney function. Medical intervention is usually required to slow progression.";
} else if (gfr >= 15) {
stageText = "Stage 4 (Severe)";
stageClass = "stage-severe";
interpText = "Severe loss of kidney function. Preparation for kidney replacement therapy (dialysis or transplant) often begins here.";
} else {
stageText = "Stage 5 (Kidney Failure)";
stageClass = "stage-failure";
interpText = "Kidney failure. Dialysis or a kidney transplant is typically needed for survival.";
}
// Update UI classes
stageInfoElement.className = "stage-badge " + stageClass;
stageInfoElement.innerText = stageText;
interpretationElement.innerText = interpText;
}