The Estimated Glomerular Filtration Rate, or EGFr, blood test measures the level of creatine in the bloodstream, according to the American Kidney Fund. Creatine is produced by the muscles and normally filtered out by the kidneys, so a low EGFr rate may indicate kidney disease.
Normal ranges for the EGFr test are between 60 and 120, as reported by the American Kidney Fund. Rates lower than 60 may indicate a kidney problem, while rates under 15 may indicate kidney failure. The test is not always accurate for patients who are under the age of 18, pregnant, very muscular or very overweight.