Health Calculator

GFR Calculator

GFR Calculator

The glomerular filtration rate (GFR) is an essential measure of kidney function. It estimates the amount of blood that passes through the kidneys per minute, filtering out waste products and excess fluids. GFR is used to diagnose and monitor chronic kidney disease (CKD) and to adjust medication dosages to avoid harmful side effects.

It helps understand the stage of CKD (chronic kidney disease) a person may have and thus, serves as a guideline for their protein intake (since excessive protein can worsen CKD).

CKD Stage GFR Protein Requirement
5th Stage   <15ml/min 0.5gm
4th Stage   16-29ml/min 0.6gm
3rd Stage   30-59ml/min 0.65gm
2nd Stage   60-89ml/min 0.75gm
1st Stage   >90ml/min 0.8-1gm

Calculation of GFR

GFR is calculated using equations that take into account a person's age, gender, race, and serum creatinine level. Serum creatinine is a waste product that is produced by muscles and excreted by the kidneys. Its level in the blood is a good indicator of kidney function because the kidneys are responsible for filtering it out of the blood.

One commonly used GFR equation is the CKD-EPI equation, which was developed by the Chronic Kidney Disease Epidemiology Collaboration. This equation is based on data from over 8,000 people and is more accurate than previous equations in estimating GFR. The CKD-EPI equation takes into account a person's age, gender, race, and serum creatinine level to calculate GFR.

Components of the CKD-EPI equation

To use the CKD-EPI equation, you need to know the person's serum creatinine level, gender, age, and race. The serum creatinine level can be measured by a blood test. The GFR can then be calculated using the following formula:

GFR (ml/min/1.73 m²) = 141 x min(Serum creatinine/κ, 1)^α x max(Serum creatinine/κ, 1)^-1.209 x 0.993^Age x 1.018 [if female] x 1.159 [if Black]


Serum creatinine is the level of creatinine in the blood (measured in mg/dL) κ is a constant that depends on the person's gender (0.7 for females and 0.9 for males)

α is a constant that depends on the person's gender and age (0.329 for females, -0.411 for males younger than 70 years, and -0.329 for males 70 years or older)

Age is the person's age in years

Disclaimer: It is important to note that the values generated by the calculator are approximate and should only be used for reference purposes. The calculated values should not be relied upon as a definitive diagnosis or as a substitute for medical advice from a qualified healthcare professional. The accuracy of the GFR calculator may be affected by factors such as age, weight, and ethnicity, so it is important to consult with a healthcare professional for a more comprehensive evaluation of kidney function.