The breath test is a rapid test to clarify whether a patient has H. pylori infection in the clinic, with high sensitivity, high specificity, quick and easy, and inexpensive, and is widely used in the clinic at a cost of about one hundred dollars. It is mainly used for diagnosis. First, patients with dyspepsia, suspected of having H. pylori infection. Secondly, patients with acute and chronic gastritis, gastroduodenal ulcer, and then to prevent gastric cancer or patients with family history of gastric cancer. It can also be used for the evaluation of the effect and diagnosis of recurrence after H. pylori eradication treatment, as well as epidemiological investigation and screening of H. pylori infection. It should be noted that the test should be performed before the test by fasting for more than six hours and discontinuing antibiotics and bismuth for 30 days and proton pump inhibitors for about two weeks to avoid affecting the results.