Creatinine clearance usually refers to endogenous creatinine clearance, which is calculated in a number of ways and cannot be generalized. The commonly used formula is endogenous creatinine clearance = (140-age) × body weight (kg)/72 × blood creatinine (mg/dl), or endogenous creatinine clearance = [(140-age) × body weight (kg)]/0.818 × blood creatinine (umol/L), and in both cases for women, by the result of the calculation × 0.85. Endogenous creatinine clearance inspection and calculation methods are more, inulin test is the gold standard, but due to the high cost of inspection and inconvenient operation, it is not often used, clinically, blood creatinine, urinary creatinine and other tests are generally used, and then estimated by the above and other calculation formulas, but for the elderly, obesity or wasting people the accuracy is poor, and its normal value is mostly 80-120 ml/min. Clinically, endogenous creatinine clearance and glomerular filtration rate are often used to assess kidney function. It is recommended to calculate endogenous creatinine clearance and assess renal function under the guidance of a physician.