Left subcostal pain can be caused by pleural disease, stomach disease, heart disease and other diseases. 1. Pleural disease: if the pleura has strained injury or pleurisy, the symptom of subcostal pain may appear. 2. Gastric diseases: patients with gastric ulcer and gastritis may have symptoms of subcostal tenderness, which may be accompanied by nausea and loss of appetite. 3. Heart disease: some heart diseases such as coronary heart disease, myocarditis, myocardial infarction, etc., the onset of pain can radiate to the lower ribs. In addition, intercostal neuritis, herpes zoster infection and other diseases can also appear under the left rib pain. If you have unexplained pain under the left rib cage, you need to go to the hospital in time, after clarifying the cause of the disease for targeted treatment.