A gastric H. pylori blow test is performed to detect the presence of H. pylori infection in the stomach, and requires an empty stomach. The H. pylori blowing test is to take the liquid containing carbon 13 or carbon 14 before the test, when the patient exists H. pylori infection, it will produce a large amount of carbon dioxide, at this time, by checking the content of carbon 13 or carbon 14, it is clear whether it is infected with H. pylori or not, but if the patient is not fasting, the presence of food in the stomach will reduce the contact area of the gastric mucous membrane with carbon 13 or carbon 14. Secondly, if the test is not performed on an empty stomach, it is also easy to cause gastrointestinal reactions such as nausea and vomiting when the patient is drinking the liquid or blowing on the stomach. Therefore, if the patient undergoes gastric H. pylori test, he/she needs to perform the test on an empty stomach. Specific cases need to follow the doctor’s instructions.