Understanding Glomerular Filtration Rate (GFR) and eGFR
Glomerular Filtration Rate (GFR) is a key indicator of kidney function. It measures how efficiently your kidneys filter waste products and excess fluid from your blood. The glomeruli are tiny filtering units within your kidneys.
Why is GFR important?
Kidneys play a vital role in maintaining overall health by regulating blood pressure, producing red blood cells, and balancing electrolytes. When kidney function declines, waste products can build up in the body, leading to serious health complications.
What is eGFR?
Because directly measuring GFR can be complex and is not routinely done, healthcare providers often use an estimated GFR (eGFR) calculation. This calculation uses your blood serum creatinine levels, along with other factors like your age, gender, and race, to estimate your kidney function.
Common eGFR Formulas:
The most widely used formulas for estimating GFR are the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation and the MDRD (Modification of Diet in Renal Disease) study equation. This calculator uses the CKD-EPI 2021 equation for its accuracy and broad applicability across different populations.
Normal eGFR Ranges:
Generally, an eGFR of 90 or higher is considered normal for younger adults. However, GFR naturally declines with age.
eGFR > 90 mL/min/1.73m²: Normal kidney function (though this may be abnormal in the presence of other kidney damage indicators).
eGFR 60-89 mL/min/1.73m²: Mildly decreased kidney function. This could be a sign of early kidney disease, especially if it persists.
eGFR < 60 mL/min/1.73m²: Significantly decreased kidney function. This indicates moderate to severe kidney disease and requires medical attention.
eGFR < 15 mL/min/1.73m²: Kidney failure, requiring dialysis or a kidney transplant.
Factors Affecting eGFR:
Age: GFR typically decreases with age.
Gender: Men generally have a higher GFR than women due to differences in muscle mass.
Race: Certain race adjustments (historically for African Americans) were included in older equations but are being phased out in newer, more equitable formulas. The CKD-EPI 2021 equation uses a simplified approach without race coefficients.
Serum Creatinine: This waste product from muscle metabolism is filtered by the kidneys. Higher creatinine levels often indicate reduced kidney function.
Body Size: The GFR is usually normalized to body surface area (mL/min/1.73m²).
Important Note: This eGFR calculator is for informational purposes only and is not a substitute for professional medical advice. Always consult with your doctor or a qualified healthcare provider for diagnosis, treatment, and any questions you may have regarding your kidney health.
function calculateGFR() {
var age = parseFloat(document.getElementById("age").value);
var serumCreatinine = parseFloat(document.getElementById("serumCreatinine").value);
var gender = document.getElementById("gender").value;
var race = document.getElementById("race").value;
var eGFRResultElement = document.getElementById("eGFRResult");
var gfrInterpretationElement = document.getElementById("gfrInterpretation");
// Clear previous results and interpretations
eGFRResultElement.innerHTML = "";
gfrInterpretationElement.innerHTML = "";
// Validate inputs
if (isNaN(age) || age 120) {
eGFRResultElement.innerHTML = "Please enter a valid age.";
return;
}
if (isNaN(serumCreatinine) || serumCreatinine <= 0) {
eGFRResultElement.innerHTML = "Please enter a valid serum creatinine level.";
return;
}
var a = -0.2411; // CKD-EPI 2021 equation constants
var e = -1.207; // CKD-EPI 2021 equation constants
var k = 1.012; // CKD-EPI 2021 equation constants
var genderCoefficient = (gender === "male") ? 1 : 0.953;
// CKD-EPI 2021 equation (simplified, without race)
var eGFR;
var serumCreatinineForEquation = serumCreatinine;
if (gender === "male") {
if (serumCreatinineForEquation <= 0.9) {
eGFR = 133 * Math.pow(serumCreatinineForEquation / 0.9, a);
} else {
eGFR = 133 * Math.pow(serumCreatinineForEquation / 0.9, e);
}
} else { // female
if (serumCreatinineForEquation <= 0.7) {
eGFR = 125 * Math.pow(serumCreatinineForEquation / 0.7, a);
} else {
eGFR = 125 * Math.pow(serumCreatinineForEquation / 0.7, e);
}
}
eGFR = eGFR * Math.pow(Math.max(age / 70, 0.993), k); // Age adjustment
// Ensure eGFR is not less than 5 (practical lower limit often considered)
if (eGFR = 90) {
interpretation = "eGFR is within the normal range (or above 90).";
} else if (eGFR >= 60 && eGFR = 30 && eGFR = 15 && eGFR < 30) {
interpretation = "eGFR is severely decreased, indicating severe kidney disease. Prompt medical management is necessary.";
} else if (eGFR < 15) {
interpretation = "eGFR is critically low, suggesting kidney failure. Urgent medical consultation and treatment options (like dialysis or transplant) should be discussed with a doctor.";
}
gfrInterpretationElement.innerHTML = interpretation;
}
#gfr-calculator-container {
font-family: Arial, sans-serif;
max-width: 700px;
margin: 20px auto;
padding: 20px;
border: 1px solid #ddd;
border-radius: 8px;
background-color: #f9f9f9;
}
#gfr-calculator-inputs {
display: grid;
grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
gap: 15px;
margin-bottom: 20px;
}
.form-group {
display: flex;
flex-direction: column;
}
.form-group label {
margin-bottom: 5px;
font-weight: bold;
}
.form-group input[type="number"],
.form-group select {
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 1em;
}
button {
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width: 100%;
padding: 12px 15px;
background-color: #007bff;
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transition: background-color 0.3s ease;
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button:hover {
background-color: #0056b3;
}
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}
#gfr-interpretation {
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}
#gfr-explanation {
line-height: 1.6;
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}
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margin-bottom: 10px;
}
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margin-bottom: 15px;
}
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margin-left: 20px;
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}
#gfr-explanation li {
margin-bottom: 8px;
}