Glomerular filtration rate (GFR) is the best overall index of kidney function. Normal GFR varies according to age, sex, and body size, and declines with age. The National Kidney Foundation recommends using the CKD-EPI Creatinine Equation (2021) to estimate GFR. NKF and the American Society of Nephrology have convened a Task Force to focus on the use of race to estimate GFR.