A mild increase in creatine kinase 300 U/L can be associated with a number of conditions, such as in athletes after intense exercise. It is recommended to seek medical attention to determine the cause, and the exact recovery time is related to individual conditions and cannot be generalized. Creatine kinase is found in skeletal muscle and cardiac muscle, and can be used in the diagnosis of skeletal muscle disease and cardiac muscle disease. The normal reference value of serum creatine kinase is 18-198U/L. Higher levels may be related to strenuous exercise, use of drugs, etc., which is called physiologic high, and patients can recover in a few days with proper rest. However, if it is as high as 300U/L, and after excluding athletes who have performed extreme sports, it is considered to be caused by certain diseases, such as myocarditis, dermatomyositis, acute myocardial infarction, pericarditis, etc., or caused by the use of certain drugs, such as statins. Therefore, it is recommended that the patient should consult a doctor in time to clarify the cause of the disease according to other symptoms and further examination, etc., so as to carry out targeted treatment. The specific recovery time is related to the disease and cannot be specified. In conclusion, creatine kinase is one of the indicators in the examination, if abnormal elevation occurs, it is necessary to combine other indicators and symptoms to make a judgment, and it is recommended to seek medical advice from a doctor.