GFR decreases with age, so lower rates are considered normal for older adults, according to MedlinePlus. GFR stands for glomerular filtration rate, a number that indicates how well the kidneys are filtering waste from the blood.
A glomerulus is a cluster of filtering capillaries in the kidney; each kidney contains about one million glomeruli, according to the National Institute of Diabetes and Digestive and Kidney Diseases. Regular GFR testing is recommended by NIH for those suffering chronic kidney disease and for people with other chronic conditions including high blood pressure, diabetes, heart disease and repetitive urinary tract infections (UTIs). GFR levels are ascertained through a blood test.