What is a glomerular filtration rate (GFR) test?A glomerular filtration rate (GFR) is a blood test that checks how well your kidneys are working. Your kidneys have tiny filters called glomeruli. These filters help remove waste and excess fluid from the blood. A GFR test estimates how much blood passes through these filters each minute.A GFR can be measured directly, but it is a complicated test, requiring specialized providers. So GFR is most often estimated using a test called an estimated GFR or eGFR. To get an estimate, your provider will use a method known as a GFR calculator. A GFR calculator is a type of mathematical formula that estimates the rate of filtration using some or all of the following information about you:The results of a blood test that measures creatinine, a waste product filtered by the kidneysAgeWeightHeightGenderRaceThe eGFR is a simple test that can provide very accurate results.Other names: estimated GFR, eGFR, calculated glomerular filtration rate, cGFR
