The Glomerular Filtration Rate definition in the simplest terms is how well your kidneys are filtering the poisons out of your body. Normal GFR varies on age, race, nutritional parameters, creatinine level and a variety of other factors. For the ease of explanation and monitoring the major variables that change the level of your GFR are age, sex, race, and a blood test called your creatinine. These variables are entered into a complex mathematical equation which calculates your GFR. The National Kidney Foundation has outlined treatment recommendations based on the level of GFR. You will hear your doctors and staff at the Kidney and Hypertension Institute of Utah discuss your GFR and level of kidney function. The stage of kidney disease is primarily determined by GFR. The National Kidney Foundation recommends that laboratories automatically report your GFR when your blood is drawn for creatinine. To determine your GFR follow the link and see definition of Chronic Kidney Disease to determine your stage.