The molecular weight of creatinine is 113 daltons, which is a small molecule toxin. There are two main sources of creatinine in the human body, one is the product of muscle cell decomposition and metabolism, and the other is the exogenous source of meat decomposition and metabolism. Creatinine is excreted in the urine after it is filtered through the glomerulus and excreted in the renal tubules. When blood is drawn for kidney function, the normal range of blood creatinine is between 40-110umol/L. If there is an increase in creatinine, it often indicates renal insufficiency, and it is necessary to go to the hospital in time to improve urinary routine, 24HUP quantification, endogenous creatinine clearance as well as renal function, immune function and other related tests to further clarify the diagnosis. If there is a decrease in creatinine, it may indicate malnutrition or early kidney disease with increased glomerular filtration rate and in a state of hyperfiltration and hyperperfusion.