Tubular reabsorption of phosphorus/Glomerular filtration rate and Serum or Plasma

Estimated glomerular filtration rate (eGFR) and GFR tests check how well your kidneys are working. Your kidneys are two organs on either side of your spine just below your rib cage. They have tiny filters called glomeruli. These filters remove waste and extra water from your blood and get rid of them through your urine (pee).

An eGFR and mGFR test are used to see if your kidneys are filtering waste at a healthy rate. If they filter waste too slowly, it could be a sign that your kidneys have been damaged by kidney disease.