GFR in clinical terms means glomerular filtration rate. In clinical practice, the stage of chronic kidney disease is judged by the glomerular filtration rate, which is around 100 ml/min (80-120 ml/min) in normal people. With the increase of age, the glomerular filtration rate will decrease by 5-10 ml/min for every 10 years of growth after 40 years old. when the glomerular filtration rate is less than 50 ml/min, creatinine will be higher than normal, so the residual kidney function can be judged by the amount of glomerular filtration rate. When the glomerular filtration rate is above 50 ml/min, normal renal function can occur, i.e., compensatory phase, and patients can have no clinical manifestations. When the glomerular filtration rate is less than 50 ml/min or below, creatinine can be elevated, accompanied by general discomfort such as anorexia, poor appetite, nausea, vomiting, edema, deep breathing, irritability, unconsciousness, and rash.