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GFR by Age Calculator (CKD-EPI 2009)

Serum Creatinine (mg/dL):

Age (years):

Sex: Male Female

Race: Non-African American African American

Estimated GFR:

Understanding Your GFR by Age: A Comprehensive Guide

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 optimally, while a decreased GFR can signal kidney disease.

What is GFR?

GFR represents the volume of fluid filtered from the blood into the Bowman's capsule per unit of time. Essentially, it tells you how many milliliters of blood your kidneys clean per minute. Because GFR naturally declines with age, understanding your GFR in the context of your age is vital for accurate health assessment.

Why is GFR Important?

Monitoring GFR is essential for:

Detecting Kidney Disease Early: A low GFR is often the first sign of chronic kidney disease (CKD), allowing for early intervention.
Staging Kidney Disease: GFR values are used to classify the stages of CKD, guiding treatment plans and prognosis.
Monitoring Disease Progression: Regular GFR checks help track how quickly kidney function is declining.
Medication Dosing: Many medications are cleared by the kidneys, and dosages may need adjustment based on GFR to prevent toxicity.

How is GFR Estimated? The CKD-EPI Equation

Direct measurement of GFR is complex and rarely done in routine clinical practice. Instead, GFR is estimated using formulas that incorporate readily available blood test results, primarily serum creatinine, along with demographic factors like age, sex, and race.

Our calculator uses the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation from 2009. This formula is widely recommended by medical organizations because it is generally more accurate than older equations (like MDRD) and has been validated across diverse populations. It accounts for:

Serum Creatinine: A waste product from muscle metabolism, creatinine levels in the blood rise as kidney function declines.
Age: Kidney function naturally decreases with age.
Sex: Men and women typically have different muscle mass, affecting creatinine levels.
Race: The CKD-EPI equation includes a factor for African Americans, as they tend to have higher average creatinine levels for a given GFR.

Interpreting Your GFR Results

GFR values are typically reported in milliliters per minute per 1.73 square meters (mL/min/1.73m²), which normalizes the result to an average body surface area.

GFR ≥ 90 mL/min/1.73m²: Considered normal kidney function.
GFR 60-89 mL/min/1.73m²: Mildly decreased kidney function (Stage 2 CKD). Often, there are no symptoms at this stage.
GFR 45-59 mL/min/1.73m²: Mild to moderate decreased kidney function (Stage 3a CKD).
GFR 30-44 mL/min/1.73m²: Moderate to severe decreased kidney function (Stage 3b CKD). Symptoms may start to appear.
GFR 15-29 mL/min/1.73m²: Severely decreased kidney function (Stage 4 CKD). Significant symptoms are likely.
GFR < 15 mL/min/1.73m²: Kidney failure (Stage 5 CKD). This stage often requires dialysis or kidney transplantation.

Example Calculation

Let's consider an example:

Serum Creatinine: 1.0 mg/dL
Age: 45 years
Sex: Male
Race: Non-African American

Using the CKD-EPI formula:

For a male with Scr > 0.9 mg/dL (since 1.0 > 0.9):

GFR = 141 * (Scr / 0.9)^-1.209 * (0.993)^Age

GFR = 141 * (1.0 / 0.9)^-1.209 * (0.993)^45

GFR = 141 * (1.111)^-1.209 * (0.730)

GFR = 141 * 0.889 * 0.730 ≈ 91.5 mL/min/1.73m²

This result would indicate normal kidney function (GFR ≥ 90).

Important Disclaimer

This GFR calculator provides an estimate based on the CKD-EPI 2009 equation. It is intended for informational purposes only and 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.