Creatinine clearance generally refers to endogenous creatinine clearance, which refers to the total removal of intrinsic creatinine from a number of milliliters of blood by the kidneys per unit of time, and can reflect the glomerular filtration rate, which allows you to determine the impairment of renal function. Creatinine is a metabolite of creatine. Under normal conditions, the body produces creatinine and releases creatinine at a constant rate. The produced creatinine is filtered through the kidneys and excreted with urine. Creatinine has a relatively small molecular weight, passes freely through the glomeruli, and is not reabsorbed by the renal tubules. Since the rate of creatinine production is relatively constant, when renal impairment occurs, the glomerular filtration of creatinine decreases, resulting in the inability to metabolize creatinine into the urine, a rise in creatinine levels in the blood, high blood creatinine, and a decrease in creatinine clearance. When creatinine clearance decreases, it is recommended to consult a doctor in time to investigate the cause of renal function injury, make a clear diagnosis, and standardize the treatment under the guidance of physician.