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Good to Know
This is a screening estimate only, not a diagnosis — a real assessment of kidney function requires a clinician's interpretation alongside other factors, and typically more than one test over time.
Disclaimer
This calculator provides estimates for informational purposes only and does not constitute financial, medical, legal, or tax advice. Always consult a qualified professional about your specific situation.
How This Calculator Works
eGFR (estimated Glomerular Filtration Rate) is a screening measure of how well the kidneys are
filtering blood, estimated from a routine blood test result (serum creatinine) plus age and gender.
It’s the single most commonly used lab value for tracking kidney function over time. Enter your
gender at birth, age, and serum creatinine (from a recent blood test — it will be printed on your
lab report), and this calculator estimates your eGFR and which standard Chronic Kidney Disease
(CKD) stage it falls into.
This calculator uses the 2021 CKD-EPI Creatinine Equation, the current formula endorsed by the
National Kidney Foundation and American Society of Nephrology. It replaced an earlier version of
the same equation that included a race coefficient — the current, race-free version is now the
standard used across U.S. clinical practice.
The Formula
The equation is centered on a per-gender creatinine “pivot point” (kappa): 0.7 mg/dL for women, 0.9
mg/dL for men. At or below that pivot, a gentler exponent applies; above it, a steeper one always
applies:
where Scr is serum creatinine in mg/dL, κ is 0.7 (women) or 0.9 (men),
α is −0.241 (women) or −0.302 (men), Age is in years, and
S is a fixed multiplier of 1.012 for women or 1 for men. In plain terms: the
formula compares your creatinine to your gender’s typical range, then adjusts down for age, since
kidney function naturally declines slowly over a lifetime.
The result is then compared against the standard CKD staging system:
Stage
eGFR (mL/min/1.73m²)
Description
G1
90 or above
Normal kidney function
G2
60–89
Mildly decreased
G3a
45–59
Mildly to moderately decreased
G3b
30–44
Moderately to severely decreased
G4
15–29
Severely decreased
G5
Below 15
Kidney failure
Worked Example
A female, age 50, with a serum creatinine of 0.8 mg/dL (above her 0.7 mg/dL pivot
point, so the steeper −1.200 exponent applies):
0.8÷0.7≈1.1429, raised to the power of
−1.2≈0.8519.
0.993850≈0.7328.
142×0.8519×0.7328×1.012≈89.7.
An eGFR of about 89.7 mL/min/1.73m² falls right at the boundary between G1 (Normal) and
G2 (Mildly Decreased) — landing in G2.
Cómo funciona esta calculadora
El eGFR (tasa de filtración glomerular estimada) es una medida de detección de qué tan bien
están filtrando la sangre los riñones, estimada a partir del resultado de un análisis de sangre de
rutina (creatinina sérica) más la edad y el género. Es el valor de laboratorio más utilizado para
dar seguimiento a la función renal a lo largo del tiempo. Ingresa tu género al nacer, tu edad y tu
creatinina sérica (de un análisis de sangre reciente — aparecerá impresa en tu reporte de
laboratorio), y esta calculadora estima tu eGFR y en qué etapa estándar de Enfermedad Renal Crónica
(ERC) se ubica.
Esta calculadora utiliza la Ecuación de Creatinina CKD-EPI 2021, la fórmula actual respaldada
por la National Kidney Foundation y la American Society of Nephrology. Reemplazó una versión
anterior de la misma ecuación que incluía un coeficiente de raza — la versión actual, libre de
raza, es ahora el estándar utilizado en toda la práctica clínica de Estados Unidos.
La fórmula
La ecuación se centra en un “punto de referencia” (kappa) de creatinina específico por género: 0.7
mg/dL para mujeres, 0.9 mg/dL para hombres. En ese punto de referencia o por debajo de él, se
aplica un exponente más suave; por encima de él, siempre se aplica uno más pronunciado:
donde Scr es la creatinina sérica en mg/dL, κ es 0.7 (mujeres) o 0.9
(hombres), α es −0.241 (mujeres) o −0.302 (hombres), Edad está en años,
y S es un multiplicador fijo de 1.012 para mujeres o 1 para hombres. En términos
sencillos: la fórmula compara tu creatinina con el rango típico de tu género, y luego ajusta hacia
abajo según la edad, ya que la función renal naturalmente declina de forma lenta a lo largo de la
vida.
El resultado se compara luego con el sistema estándar de etapificación de la ERC:
Etapa
eGFR (mL/min/1.73m²)
Descripción
G1
90 o más
Función renal normal
G2
60–89
Levemente disminuida
G3a
45–59
Levemente a moderadamente disminuida
G3b
30–44
Moderadamente a severamente disminuida
G4
15–29
Severamente disminuida
G5
Menos de 15
Falla renal
Ejemplo resuelto
Una mujer, de 50 años, con una creatinina sérica de 0.8 mg/dL (por encima de su punto
de referencia de 0.7 mg/dL, por lo que se aplica el exponente más pronunciado de −1.200):
0.8÷0.7≈1.1429, elevado a la potencia de
−1.2≈0.8519.
0.993850≈0.7328.
142×0.8519×0.7328×1.012≈89.7.
Un eGFR de aproximadamente 89.7 mL/min/1.73m² cae justo en el límite entre G1 (Normal) y
G2 (Levemente Disminuida) — ubicándose en G2.
eGFR (estimated Glomerular Filtration Rate) is a screening measure of how well your kidneys filter blood, estimated from a routine blood test (serum creatinine) plus your age and gender. It's the most commonly used lab value for tracking kidney function.
What do the CKD stages mean?
The stages (G1 through G5) describe how much kidney function is estimated to remain, from Normal (G1) down to Kidney Failure (G5). A single result is a screening snapshot, not a diagnosis — kidney function is normally tracked with more than one test over time.
Why does this calculator no longer ask for race?
This calculator uses the 2021 CKD-EPI race-free equation, the current standard endorsed by the National Kidney Foundation and American Society of Nephrology, which replaced an earlier version of the same equation that included a race coefficient.
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