The glomerular filtration rate, or GFR, is an estimate of how well kidneys are filtering waste from the blood, notes WebMD. A lab specialist calculates the GFR using a formula based on the measured blood creatinine level and other factors, including age, ethnicity, gender and size of the patient.
The glomerular filtration rate, also called eGFR or Estimated GFR, estimates the volume of blood passing through tiny filters in the kidney each minute, according to MedlinePlus. The normal range for GFR is approximately 90 to 120 milliliters per minute per 1.73 meters squared.
The tiny kidney filters, known as glomeruli, filter the blood more slowly in a person with chronic kidney disease. This slow filtration causes a GFR that is consistently below normal. A patient in kidney failure, indicated by a GFR below 15 milliliters per minute per 1.73 meters squared, requires immediate medical attention, says MedlinePlus.