How to Calculate Glomerular Filtration Rate with a Serum Creatinine

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eGFR Calculator (CKD-EPI 2021 Equation)

Estimated GFR (eGFR):
mL/min/1.73m²

Understanding How to Calculate Glomerular Filtration Rate

The Glomerular Filtration Rate (GFR) is the best overall index of kidney function. It describes the flow rate of filtered fluid through the kidney. Since direct measurement of GFR is complicated and invasive, clinicians use "estimated GFR" (eGFR) calculated from a blood test called Serum Creatinine.

The Role of Serum Creatinine

Creatinine is a waste product produced by muscle metabolism. Healthy kidneys filter creatinine from the blood and pass it into the urine. If kidney function declines, creatinine levels in the blood rise. However, creatinine production depends on muscle mass, which is why age and sex are critical variables in the calculation.

The CKD-EPI 2021 Formula

This calculator uses the 2021 CKD-EPI Creatinine Equation. This modern standard is designed to be more accurate across various populations and intentionally removes race as a variable to ensure clinical equity. The math involves complex exponents:

  • Female: 142 × min(Scr/0.7, 1)-0.241 × max(Scr/0.7, 1)-1.200 × 0.9938Age
  • Male: 142 × min(Scr/0.9, 1)-0.302 × max(Scr/0.9, 1)-1.200 × 0.9938Age

Interpretation of GFR Results

GFR Level Stage Meaning
90 or above Stage 1 Normal or High Function
60 to 89 Stage 2 Mildly Decreased
30 to 59 Stage 3 Moderate Decrease
15 to 29 Stage 4 Severe Decrease
Below 15 Stage 5 Kidney Failure

Disclaimer: This calculator is for educational purposes only. Always consult with a healthcare professional for diagnosis and treatment of kidney disease.

function calculateGFR() { var scr = parseFloat(document.getElementById('scValue').value); var age = parseFloat(document.getElementById('ageValue').value); var gender = document.querySelector('input[name="gender"]:checked').value; if (isNaN(scr) || isNaN(age) || scr <= 0 || age = 90) { stageText = "Stage 1: Normal or High Kidney Function"; stageColor = "#27ae60"; } else if (gfrResultValue >= 60) { stageText = "Stage 2: Mildly Decreased Kidney Function"; stageColor = "#82c91e"; } else if (gfrResultValue >= 30) { stageText = "Stage 3: Moderately Decreased Kidney Function"; stageColor = "#f39c12"; } else if (gfrResultValue >= 15) { stageText = "Stage 4: Severely Decreased Kidney Function"; stageColor = "#e67e22"; } else { stageText = "Stage 5: Kidney Failure (ESRD)"; stageColor = "#c0392b"; } stageBox.innerText = stageText; stageBox.style.color = stageColor; display.scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }

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