The claim that omeprazole causes cancer may be true. Omeprazole is a proton pump inhibitor commonly used in clinical practice, which can inhibit the secretion of gastric acid. Long-term use of omeprazole may lead to vomiting, diarrhea, constipation, abdominal pain, abdominal distension and other adverse reactions, and patients are generally not recommended to take it for more than three months in a row. If long-term medication is needed, it must be guided by a professional doctor. However, since patients with Zuo-Ai syndrome need to receive long-term treatment with omeprazole, gastroduodenal carcinoid may occur according to clinical reports. Therefore, the claim that Omeprazole causes cancer may be true. Patients are advised to use Omeprazole under the guidance of a professional doctor and not to take it privately to avoid causing adverse drug reactions.