Pain in the left shoulder must be a problem in the body for the appropriate symptoms to appear, just a matter of how mild or severe it is. Pain is a reaction of the body and that kind of stress response, which often suggests a local abnormality or an abnormality in a related area. There are several common causes of left shoulder pain: the first one is frozen shoulder, strain or acute injury around the shoulder joint, and these can cause pain. Secondly, cervical spondylosis can also cause shoulder pain. Third, some heart diseases, such as coronary artery disease and angina pectoris, can also reflexively cause pain in the left shoulder, which is often an early symptom, so it can also be used as a sign of heart disease. If the pain appears, you can first observe the characteristics of the pain and the related area, and if the symptoms are not very serious, you can support symptomatic treatment. If the pain is very severe and accompanied by other chest tightness and shortness of breath, dizziness or coughing, coughing or fever, you must seek medical attention promptly.