Left subcostal pain may be caused by physiological reasons, or it may be caused by pathological reasons such as intercostal neuralgia, rib muscle injury, pleural lesions and other diseases. 1. Physiological causes: improper posture, strenuous exercise may lead to left subcostal pain. 2. Intercostal neuralgia: the phenomenon of left subcostal pain is mostly caused by intercostal neuralgia. The pain is usually located at the edge of the ribs, and the pain is paroxysmal and localized. It is usually triggered by fatigue, lack of sleep or low immunity. 3. Rib muscle injury: If you are subjected to strong external impact or pulling movement, it may lead to muscle tissue injury in the rib area, which may cause the left subcostal pain phenomenon. 4. Pleural lesions: pleural lesions can cause left subcostal pain, usually in deep breathing or deep inhalation when the pain will be significantly aggravated, need to improve the chest CT examination to clarify the diagnosis, if necessary, also need to carry out thoracocentesis. If the left side of the subcostal pain, it is recommended to go to the hospital in a timely manner, after the cause is clear and symptomatic treatment, the patient should rest as much as possible in life, avoid physical exertion.