An upset stomach at 6 p.m. can be caused by duodenal ulcer, indigestion or gastritis, which can be treated with medications such as omeprazole. 1. Duodenal ulcer: it is an ulcer caused by digestion of gastrointestinal mucosa by gastric juice. It can be caused by excessive secretion of gastric juice after complete digestion of food in the stomach, which enters the duodenum and irritates the ulcer surface, thus causing abdominal pain. Omeprazole and other drugs can be used to treat. 2. Indigestion: due to emotional stress, gastrointestinal inflammation can cause gastrointestinal tract power disorders and lead to indigestion, so that the food eaten at noon can not be well digested and stay in the gastrointestinal tract, fermentation and gas production, resulting in abdominal distension, belching and other discomforts. Available drugs such as omeprazole, domperidone and other treatment. 3. Gastritis: abuse of non-steroidal anti-inflammatory drugs such as aspirin, long-term smoking and drinking, pathogenic bacterial infections can cause gastritis, manifested as epigastric discomfort, nausea, vomiting, etc., can be felt in the afternoon stomach discomfort, can be treated with drugs such as omeprazole and other acid-suppressing drugs, pectin bismuth and other gastric mucosal protection drugs. There may also be other diseases that can cause stomach discomfort in the afternoon, in order to avoid mis-treatment and omission of treatment, please go to the hospital in time for the appropriate examination, diagnosis, and then under the guidance of the physician treatment and medication.