CREA is used to replace creatinine in clinical practice, and is generally divided into blood creatinine and urine creatinine. Blood creatinine is an important indicator used to reflect the level of toxins excreted by the kidneys, and is often used to determine whether the state of kidney function is normal. If there is an abnormality, it can appear in the case of acute renal failure or chronic renal failure, and it also needs to be combined with other relevant laboratory test criteria and the course of the disease to make a comprehensive analysis. Chronic renal failure indicators are also divided into four periods, which are phase I, phase II, phase III and phase IV of chronic renal failure, used to represent and judge the state of renal function.