A low eGFR blood test of less than 60 suggests kidney disease, according to the National Kidney Fund. A level of less than 15 indicates kidney failure and requires immediate medical attention.
The estimated glomerular filtration rate measures how well tiny filters known as glomeruli in the kidney are filtering blood, says MedlinePlus. The eGFR is based on a blood test for creatinine, a waste product produced by muscle activity and normally removed by the kidney, according to the National Kidney Foundation. The test may not be accurate in persons who are younger than 18, pregnant, very overweight or very muscular, the fund says.