Glomerular filtration rate is a measure of how well your kidneys are working.

Glomerular Filtration Rate refers to the amount of blood that is filtered by the glomeruli per minute.

As kidney function declines due to damage or disease, the filtration rate decreases, and waste products begin to build up in the blood.

The estimated glomerular filtration rate (eGFR) represents the best routinely available measurement of kidney function.

The estimated glomerular filtration rate is calculated according to the formulae recommended by the National Kidney Foundation

using measured test results of blood creatinine levels and in special circumstances blood cystatin C levels.

Different equations may be used to calculate estimated glomerular filtration rate.

If you have had a recent creatinine or cystatin C measurement,

you can calculate the estimated glomerular filtration rate by using one of the calculators

for people 19 years of age or older on the National Kidney Foundation website.

If you have questions about the interpretation of your results, it is best to consult with your healthcare provider.

For children and teens younger than 19, see the pediatric estimated glomerular filtration rate calculator on the National Kidney Foundation website.

The estimated glomerular filtration rate equations are not valid for those who are 70 years of age or older because muscle mass normally decreases with age.

The estimated glomerular filtration rate may be affected by a variety of drugs, such as gentamicin, cisplatin, and cefoxitin,

that increase creatinine levels, and by any condition that decreases blood flow to the kidneys.

The calculation of estimated glomerular filtration rate is intended to be used when kidney function and creatinine/cystatin C production are stable.

If a creatinine or cystatin C level is measured when the kidney function is changing rapidly,

such as with acute kidney injury, then it will not give a useful estimate of the filtration rate.