Estimated Glomerular Filtration Rate (eGFR) Calculator
Estimated GFR: " + gfr.toFixed(2) + " mL/min/1.73m²
"; resultDiv.innerHTML += "Interpretation (CKD Stages):"; if (gfr >= 90) { resultDiv.innerHTML += "Stage 1: GFR ≥ 90 mL/min/1.73m² – Normal or high GFR. Kidney damage may be present."; } else if (gfr >= 60 && gfr < 90) { resultDiv.innerHTML += "Stage 2: GFR 60-89 mL/min/1.73m² – Mildly decreased GFR. Kidney damage may be present."; } else if (gfr >= 45 && gfr < 60) { resultDiv.innerHTML += "Stage 3a: GFR 45-59 mL/min/1.73m² – Mild-to-moderately decreased GFR."; } else if (gfr >= 30 && gfr < 45) { resultDiv.innerHTML += "Stage 3b: GFR 30-44 mL/min/1.73m² – Moderately-to-severely decreased GFR."; } else if (gfr >= 15 && gfr < 30) { resultDiv.innerHTML += "Stage 4: GFR 15-29 mL/min/1.73m² – Severely decreased GFR."; } else { // gfr < 15 resultDiv.innerHTML += "Stage 5: GFR < 15 mL/min/1.73m² – Kidney failure."; } resultDiv.innerHTML += "Note: These stages are for general information and should be interpreted by a healthcare professional. This calculator uses the CKD-EPI (2009) equation."; }Understanding Your Glomerular Filtration Rate (GFR)
The Glomerular Filtration Rate (GFR) is a crucial indicator of kidney health. It measures how well your kidneys are filtering waste products from your blood. A healthy GFR means your kidneys are functioning effectively, while a decreased GFR can signal kidney damage or disease.
What is GFR and Why is it Important?
Your kidneys contain millions of tiny filters called glomeruli. These glomeruli filter about 180 liters of blood every day, removing toxins, excess salts, and water, which are then excreted as urine. GFR is the rate at which this filtering process occurs. It's considered the best overall measure of kidney function.
Monitoring GFR is vital for:
- Detecting Kidney Disease: Early detection of chronic kidney disease (CKD) allows for timely intervention to slow its progression.
- Staging CKD: GFR values are used to classify the stage of kidney disease, guiding treatment plans.
- Medication Dosing: Many medications are cleared by the kidneys, and their dosages need to be adjusted based on GFR to prevent toxicity.
- Assessing Treatment Effectiveness: Changes in GFR can indicate whether treatments for kidney conditions are working.
How is GFR Estimated?
Directly measuring GFR is complex and usually involves specialized tests. Therefore, GFR is most commonly estimated (eGFR) using formulas that incorporate readily available blood test results, primarily serum creatinine, along with demographic factors like age, sex, and sometimes race.
The calculator above uses the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) 2009 equation. This equation is widely recommended because it is generally more accurate than older formulas, especially for individuals with normal or mildly reduced kidney function.
Inputs for the GFR Calculator:
- Serum Creatinine (mg/dL): Creatinine is a waste product from muscle metabolism. Healthy kidneys filter creatinine efficiently. When kidney function declines, creatinine levels in the blood rise. This value is obtained from a standard blood test.
- Age (Years): Kidney function naturally declines with age, so age is an important factor in estimating GFR.
- Sex: Biological sex influences muscle mass and creatinine production, which are factored into the GFR equation.
- Race: Historically, race (specifically "Black" vs. "Non-Black") has been included in GFR equations due to observed differences in average creatinine levels. However, the use of race in medical algorithms is currently under review and debate due to concerns about health equity and potential biases. While this calculator includes it for accuracy based on the CKD-EPI 2009 formula, it's important to discuss this with your healthcare provider.
Interpreting Your GFR Results (CKD Stages)
GFR values are categorized into stages of Chronic Kidney Disease (CKD):
- Stage 1: GFR ≥ 90 mL/min/1.73m² – Normal or high GFR. Kidney damage may be present (e.g., protein in urine).
- Stage 2: GFR 60-89 mL/min/1.73m² – Mildly decreased GFR. Kidney damage may be present.
- Stage 3a: GFR 45-59 mL/min/1.73m² – Mild-to-moderately decreased GFR.
- Stage 3b: GFR 30-44 mL/min/1.73m² – Moderately-to-severely decreased GFR.
- Stage 4: GFR 15-29 mL/min/1.73m² – Severely decreased GFR.
- Stage 5: GFR < 15 mL/min/1.73m² – Kidney failure.
Example Calculation:
Let's consider a 60-year-old Non-Black female with a serum creatinine of 0.9 mg/dL.
- Serum Creatinine: 0.9 mg/dL
- Age: 60 years
- Sex: Female
- Race: Non-Black
Using the CKD-EPI 2009 formula for a female with SCr > 0.7 mg/dL:
GFR = 144 * (0.9 / 0.7)^-1.209 * (0.993)^60
GFR = 144 * (1.2857)^-1.209 * (0.993)^60
GFR = 144 * 0.730 * 0.656
Estimated GFR ≈ 68.9 mL/min/1.73m²
This result would place her in CKD Stage 2 (Mildly decreased GFR).
Important Disclaimer:
This calculator provides an estimated GFR based on the CKD-EPI 2009 equation and is for informational purposes only. It should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider for any health concerns or before making any decisions related to your health or treatment.