GFR Calculator (CKD-EPI)

Estimate Glomerular Filtration Rate for Chronic Kidney Disease (CKD) staging.

Age

Gender

Race Used for CKD-EPI calculation only.

Serum Creatinine (mg/dL) Lab test result required.

Glomerular Filtration Rate

Estimated GFR ($mL/min/1.73m^2$)

CKD Stage

CKD Stage Interpretation

The GFR score determines the Chronic Kidney Disease (CKD) stage.

The GFR Calculator and Chronic Kidney Disease Staging

The **GFR Calculator** is an indispensable medical tool for measuring **kidney function** and diagnosing **Chronic Kidney Disease (CKD)**. The **Glomerular Filtration Rate (GFR)** represents the volume of fluid filtered from the blood into the kidney tubules per unit of time. A low GFR indicates impaired filtration capacity, suggesting potential **CKD**. This calculation utilizes the **CKD-EPI formula**, which is currently the most recommended method due to its improved accuracy over previous equations.

Understanding the CKD-EPI Formula

The **CKD-EPI formula** uses **serum creatinine** (a waste product filtered by the kidneys), **age**, **gender**, and **race** (specifically, 'Black' or 'Non-Black') to estimate GFR. It is more complex than a simple calculation, relying on exponents and various coefficients. The GFR result is standardized to **$mL/min/1.73m^2$** (per square meter of body surface area). The formula is sensitive to variations in muscle mass (reflected by creatinine), hence the adjustment factors for **gender** and **race**.

The Five Stages of CKD

The **GFR score** is used to determine the **CKD stage**:

**Stage 1:** GFR $\geq 90$ (Kidney damage with normal/high GFR)
**Stage 2:** GFR $60-89$ (Mild decrease)
**Stage 3:** GFR $30-59$ (Moderate decrease)
**Stage 4:** GFR $15-29$ (Severe decrease)
**Stage 5:** GFR $< 15$ (Kidney failure)

If your **GFR score** falls below $60$, further investigation by a nephrologist is typically necessary for accurate **CKD staging** and management.

GFR Calculator FAQs

Why is GFR the best marker for kidney function?

**GFR** directly measures the filtration capability of the kidneys, unlike blood pressure or simple **serum creatinine** levels. It provides a standardized rate, essential for diagnosing **Chronic Kidney Disease** early and performing accurate **CKD staging**.

What is the role of Creatinine in the CKD-EPI formula?

**Serum creatinine** is the primary input, as it is a waste product continuously produced by muscle breakdown and excreted by the kidneys. If **creatinine** levels are high in the blood, it indicates the kidneys are not filtering efficiently, resulting in a low estimated **GFR score**.

Does the GFR change as a person gets older?

Yes. **GFR** naturally declines with age, which is why **age** is a crucial component of the **CKD-EPI formula**. The calculation adjusts the result to account for the normal physiological decline in **kidney function** that occurs as part of the aging process.