The carbon 14 breath test can only be done on an empty stomach for more than two hours, and clinically it is most appropriate to complete the carbon 14 breath test on an empty stomach in the morning. Carbon 14 breath test is mainly to diagnose whether there is H. pylori infection, when the human body swallowed urea pills containing carbon 14 marker to reach the stomach, if there is H. pylori in the stomach, H. pylori secrete a urease enzyme to break down the urea. When the body is measured to exhale carbon dioxide containing labeled carbon dioxide, the degree of H. pylori infection can be inferred, to try to do it on an empty stomach or two hours after a meal, if once eating or there is still food in the stomach will have some effect on the results.