Gfr Calculator

The Glomerular Filtration Rate (GFR) is one of the most important tests used to assess kidney function. It estimates how much blood passes through the glomeruli—the tiny filters in your kidneys—each minute. A GFR test is crucial for detecting kidney disease in its early stages and for monitoring its progression.

How is GFR Calculated?

A direct measurement of GFR is complex. Therefore, healthcare professionals use a formula to estimate it (eGFR). The most commonly used formula is the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, which is utilized by this calculator. It considers several factors:

• Serum Creatinine Level: Creatinine is a waste product from muscle metabolism. Healthy kidneys filter it out of the blood. A higher level in the blood suggests the kidneys are not filtering efficiently.
• Age: Kidney function naturally declines with age.
• Sex: Men generally have more muscle mass than women, leading to different baseline creatinine levels.
• Race: The original CKD-EPI equation included a coefficient for Black individuals due to population studies showing, on average, higher creatinine levels for the same level of kidney function. However, the use of this race-based variable is now being phased out in many institutions in favor of newer, race-free equations to address health equity concerns. This calculator uses the updated 2021 CKD-EPI equation which does not use race as a variable.

The formula is complex, which is why a calculator is an invaluable tool for both patients and healthcare providers.

Interpreting Your GFR Results

GFR is measured in milliliters per minute per 1.73 square meters of body surface area (mL/min/1.73m²). The results are typically categorized into stages of kidney disease:

• Stage 1: GFR 90 or higher - Normal kidney function, but there may be other signs of kidney disease (like protein in the urine).
• Stage 2: GFR 60-89 - Mildly decreased kidney function.
• Stage 3a: GFR 45-59 - Mild to moderately decreased kidney function.
• Stage 3b: GFR 30-44 - Moderate to severely decreased kidney function.
• Stage 4: GFR 15-29 - Severely decreased kidney function.
• Stage 5: GFR less than 15 - Kidney failure, often requiring dialysis or a kidney transplant.

It's important to note that a single GFR result is not enough for a diagnosis. A trend of decreasing GFR over at least three months is typically required to diagnose chronic kidney disease (CKD).