eGFR Calculator (CKD-EPI 2021)
Understanding Your Estimated Glomerular Filtration Rate (eGFR)
The Estimated Glomerular Filtration Rate (eGFR) is a crucial measure used to assess kidney function. It indicates how well your kidneys are filtering waste products from your blood. A healthy GFR means your kidneys are working efficiently, while a lower eGFR can signal kidney disease or a decline in kidney function.
What is GFR?
GFR stands for Glomerular Filtration Rate. The glomeruli are tiny filters in your kidneys that remove waste and excess water from your blood. GFR measures the rate at which these filters are working. Since directly measuring GFR is complex and invasive, healthcare providers often rely on eGFR, which is calculated using a formula based on blood test results and other personal factors.
Why is eGFR Important?
- Early Detection of Kidney Disease: A low eGFR is often the first sign of kidney disease, even before symptoms appear. Early detection allows for timely intervention to slow progression.
- Monitoring Kidney Health: For individuals with existing kidney disease, eGFR is regularly monitored to track the disease's progression and the effectiveness of treatment.
- Medication Dosing: Many medications are cleared by the kidneys. Knowing a patient's eGFR helps doctors adjust medication dosages to prevent accumulation and toxicity.
- Risk Assessment: A reduced eGFR is associated with an increased risk of cardiovascular disease and other health complications.
The CKD-EPI 2021 Equation
Our calculator uses the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) 2021 equation. This is one of the most widely accepted and accurate formulas for estimating GFR. It was developed to provide a more precise estimate of GFR, particularly at higher GFR values, and importantly, it does not include race as a variable, addressing concerns about health equity.
The CKD-EPI 2021 equation uses the following inputs:
- Serum Creatinine (mg/dL): Creatinine is a waste product from muscle metabolism. Healthy kidneys filter creatinine out of the blood. Higher levels of creatinine in the blood can indicate reduced kidney function.
- Age (years): Kidney function naturally declines with age.
- Sex: Biological sex influences muscle mass and, consequently, creatinine levels.
The formula is:
eGFR = 142 × min(Scr/κ, 1)α × max(Scr/κ, 1)-1.200 × 0.9938Age × (1.012 if female)
Where:
- κ (kappa) is 0.7 for females and 0.9 for males.
- α (alpha) is -0.241 for females and -0.302 for males.
- Scr is serum creatinine in mg/dL.
Interpreting Your eGFR Results
eGFR values are typically categorized into stages of Chronic Kidney Disease (CKD):
- eGFR 90 mL/min/1.73 m² or higher: Normal kidney function.
- eGFR 60-89 mL/min/1.73 m²: Mildly decreased kidney function. Often, there are no symptoms at this stage, but it's important to monitor.
- eGFR 45-59 mL/min/1.73 m²: Mild to moderate decrease in kidney function.
- eGFR 30-44 mL/min/1.73 m²: Moderate to severe decrease in kidney function.
- eGFR 15-29 mL/min/1.73 m²: Severely decreased kidney function.
- eGFR less than 15 mL/min/1.73 m²: Kidney failure, often requiring dialysis or kidney transplant.
It's important to remember that an eGFR result is just one piece of information. Your doctor will consider your overall health, medical history, and other test results to make a diagnosis and recommend a course of action. Always discuss your eGFR results with a healthcare professional.
Examples of eGFR Calculation:
Example 1: Healthy Male
- Serum Creatinine: 1.0 mg/dL
- Age: 45 years
- Sex: Male
- eGFR Result: Approximately 95.2 mL/min/1.73 m² (Normal kidney function)
Example 2: Female with Mildly Decreased Function
- Serum Creatinine: 1.2 mg/dL
- Age: 60 years
- Sex: Female
- eGFR Result: Approximately 58.7 mL/min/1.73 m² (Mildly decreased kidney function, Stage 3a CKD)
Example 3: Male with Moderate Decrease
- Serum Creatinine: 1.8 mg/dL
- Age: 70 years
- Sex: Male
- eGFR Result: Approximately 39.5 mL/min/1.73 m² (Moderate to severe decrease, Stage 3b CKD)