The causes of pain in the left upper abdomen are quite varied, and there may be gastric ulcer, gastritis, pancreatitis and so on. 1. Gastric ulcer: when gastric ulcer occurs, it mainly manifests as pain in the middle and upper abdomen, and some patients can also manifest as pain in the left upper abdomen, which needs to be clarified by gastroscopy to determine whether the gastric mucosa has ulcers. 2. Gastritis: when the patient has gastritis, the left upper abdominal pain will also occur, it is recommended to pay attention to dietary regulation, do not eat some cold and spicy stimulating food, through the gastroscopy to determine the gastric mucosal congestion, edema, etc., also need to assess whether there is the presence of Helicobacter pylori infection. 3. Pancreatitis: The pain in patients with pancreatic inflammation can be located in the left upper abdomen, and the degree of pain is more serious, and can be alleviated by bending over and holding the abdomen and other forced positions, and need to consult a doctor in a timely manner. There may also be other reasons, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, give targeted treatment or treatment.