Test Details: The estimated glomerular filtration rate (eGFR) is a test that measures your level of kidney function and determines your stage of kidney disease. Your healthcare team can calculate it from the results of your blood Creatinine test as well as from your age, body size, and gender. If your eGFR number is low, your kidneys may not be working as well as they should. People with a lower eGFR are at increased risk of having chronic kidney disease (CKD) progress to kidney failure. The sooner that kidney disease is found, the better the chance of slowing or stopping it from getting worse.