Left upper abdominal pain during inspiration may be caused by gastritis, gastric ulcer, pleurisy, trauma and so on. 1. Gastritis: the gastric mucosa is damaged and in a state of inflammation and congestion, and the increased secretion of gastric acid directly stimulates the gastric mucosa, leading to pain in the left upper abdomen when inhaling, accompanied by acid reflux, nausea, abdominal distension and other symptoms. 2. Gastric ulcer: the protective barrier of gastric mucosa is destroyed to form ulcer surface, gastric acid stimulates the ulcer surface lesion, so the left upper abdomen pain when inhaling, accompanied by abdominal distension, acid reflux, heartburn, nausea and other symptoms. 3. Pleurisy: the left pleura is infected and triggers an inflammatory reaction, causing pain in the left upper abdomen, which is more obvious when inhaling, accompanied by respiratory restriction, coughing and other symptoms. 4. Costochondritis: viral infection, tuberculosis infection, chronic strain of thoracic and rib joint ligaments, etc., which induces costochondritis on the left side, leading to left epigastric pain, which is aggravated by inhalation. 5. Trauma: the left upper abdomen is impacted, resulting in pain caused by soft tissue injury, and the pain is aggravated during activity and inhalation. There may be other reasons for the pain in the left upper abdomen during inhalation, so it is recommended to consult a doctor in time to find out the cause of the disease and treat it as soon as possible.