Creatine kinase 400 U/L is considered high, whether it is harmful or not needs to be analyzed in conjunction with the cause, physiological causes are harmless; pathological factors such as myocardial infarction or skeletal muscle diseases are harmful. Creatine kinase is mainly found in skeletal muscle and cardiac muscle, the normal value is 50~310U/L for men and 40~200U/L for women, and it is affected by age, race and physiological state, if we find 400 U/L of creatine kinase, it is obviously higher than the normal value. 1. Physiological factors: creatine kinase is elevated in newborns at birth, mainly due to skeletal muscle injury and temporary hypoxia, etc. In addition, exercise can also cause creatine kinase to increase, the degree of elevation of creatine kinase is positively correlated with the duration of the exercise and the degree of intensity, which is generally harmless, and creatine kinase can be reduced to normal after changing the physiological factors. 2. Pathological factors: common pathological factors that cause elevated creatine kinase include acute myocardial infarction, myocarditis and muscle diseases such as rhabdomyolysis, etc. These diseases are hazardous to the body, and may cause sudden cardiac death and acute renal failure. In case of abnormal creatine kinase test results, it is recommended to consult a doctor in time to clarify the cause of the disease and to carry out targeted treatment or therapy with the help of a doctor.