Renal insufficiency is generally judged by the values of creatinine and urea. If creatinine exceeds 110umol/L and urea exceeds 7.5mmol/L, the patient is considered to have renal insufficiency. Renal insufficiency is the original name, but now it is called renal failure or acute kidney injury. Renal failure refers to the gradual development of chronic kidney disease, while acute kidney injury is manifested by a sharp decline in kidney function in a short period of time due to acute injury factors. But no matter what, it represents a decrease in the detoxification ability of the kidneys. Since the detoxification ability of kidney is decreased, when assessing it, we should look for toxin-related indicators, of which urea and creatinine are the two most representative toxins. Creatinine is a product of muscle metabolism, while urea is a product of protein metabolism. These two have one thing in common, that is, they are filtered by the kidneys, but rarely reabsorbed and secreted by the kidneys, so they are better and more desirable indicators of kidney function. The normal value of creatinine is between 30-110, while the normal value of urea is between 2.5-7.5. If these two exceed the upper limit of the normal value, then it is called renal insufficiency.