The estimated glomerular filtration rate test is used to measure how well the kidneys are working by performing a creatinine test and calculating a glomerular filtration rate, according to Lab Tests Online. Doctors analyze creatinine test results with age, sex and race to calculate a eGFR score.
A eGFR test is conducted via a blood test, and it measures the amount of creatinine in the blood, a waste byproduct that comes from the muscles, according to American Kidney Fund. It is often ordered as part of a comprehensive metabolic panel, basic metabolic panel or with a blood urea nitrogen test, notes Lab Tests Online. A normal eGFR score is generally between 90 to 120 milliliters per minute, while a score below 60 may indicate kidney disease.