What is Glomerular Filtration Rate Calculation

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Glomerular Filtration Rate (GFR) Calculator

The Glomerular Filtration Rate (GFR) is a key indicator of kidney function. It measures how much blood passes through the glomeruli each minute, showing how well your kidneys are filtering waste products from your blood. This calculator estimates your GFR using the CKD-EPI creatinine equation, which is a widely used and accurate method.

Male Female
African American Other

Understanding Your GFR

The Glomerular Filtration Rate (GFR) is a crucial measurement of kidney health. It quantifies the rate at which your kidneys filter waste products from your blood. A lower GFR can indicate that your kidneys are not functioning as well as they should.

How it's Calculated: This calculator uses the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation, a standard formula that takes into account your serum creatinine level, age, gender, and race. Serum creatinine is a waste product produced by your muscles that your kidneys filter out.

Interpreting Your Results:

  • GFR ≥ 90 mL/min/1.73 m²: Generally considered normal kidney function, though other factors might indicate kidney disease.
  • GFR 60-89 mL/min/1.73 m²: Mildly decreased kidney function. It's important to discuss this with your doctor to identify potential causes and management strategies.
  • GFR < 60 mL/min/1.73 m²: Significantly decreased kidney function, indicating moderate to severe kidney disease. This requires close medical attention and management.

Important Note: This calculator provides an estimated GFR for informational purposes only. It is not a substitute for professional medical advice. Always consult with your healthcare provider for diagnosis and treatment.

CKD-EPI Equation (Simplified Explanation)

The CKD-EPI equation is complex and involves several factors. For males, the equation is:

GFR = 141 × min(Scr/κ, 1)α × max(1 – 0.329, 0.993age) × 1.06 (if Black) OR 1 (if not Black)

For females, the equation is:

GFR = 141 × min(Scr/κ, 1)α × max(1 – 0.329, 0.993age) × 0.996 (if Female) × 1.06 (if Black) OR 1 (if not Black)

Where:

  • Scr is serum creatinine in mg/dL.
  • κ (kappa) is 0.7 for males and 0.5 for females.
  • α (alpha) is -1.209 for males and -0.329 for females.
  • min and max functions are used to adjust the creatinine ratio and age terms.
  • The race factor is 1.06 for African Americans, and 1 for others.
  • The gender factor is 0.996 for females.
function calculateGFR() { var serumCreatinine = parseFloat(document.getElementById("serumCreatinine").value); var age = parseInt(document.getElementById("age").value); var gender = document.getElementById("gender").value; var race = document.getElementById("race").value; var resultDiv = document.getElementById("gfrResult"); if (isNaN(serumCreatinine) || serumCreatinine <= 0 || isNaN(age) || age 1) { scrTerm = 1; } var scrPower = Math.pow(scrTerm, alpha); var ageTerm = Math.pow(0.993, age); var gfr = 141 * scrPower * Math.max(1 – 0.329, ageTerm) * genderFactor * raceFactor; // Ensure GFR is not negative, though unlikely with CKD-EPI if (gfr < 0) { gfr = 0; } resultDiv.innerHTML = "

Estimated GFR:

" + gfr.toFixed(2) + " mL/min/1.73 m²"; } .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-container h2 { text-align: center; color: #333; margin-bottom: 20px; } .calculator-inputs { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 15px; margin-bottom: 20px; } .input-group { display: flex; flex-direction: column; } .input-group label { margin-bottom: 5px; font-weight: bold; color: #555; } .input-group input[type="number"], .input-group select { padding: 10px; border: 1px solid #ccc; border-radius: 4px; font-size: 1rem; } .input-group select { cursor: pointer; } .gfr-calculator-container button { grid-column: 1 / -1; /* Span across all columns if in a grid */ padding: 12px 20px; background-color: #007bff; color: white; border: none; border-radius: 4px; font-size: 1.1rem; cursor: pointer; transition: background-color 0.3s ease; } .gfr-calculator-container button:hover { background-color: #0056b3; } .calculator-result { margin-top: 20px; padding: 15px; border: 1px solid #e0e0e0; border-radius: 4px; background-color: #fff; text-align: center; font-size: 1.2rem; color: #333; } .calculator-result h3 { margin-top: 0; color: #007bff; } .calculator-explanation { margin-top: 30px; border-top: 1px solid #eee; padding-top: 20px; font-size: 0.95rem; line-height: 1.6; color: #444; } .calculator-explanation h3 { color: #007bff; margin-bottom: 10px; } .calculator-explanation ul { padding-left: 20px; } .calculator-explanation li { margin-bottom: 5px; }

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