The precautions for doing carbon 14 are that the patient stops using antibiotic drugs for at least one month; no upper gastrointestinal bleeding in the last week; and fasting. Carbon 14, carbon 14 breath test, can clarify whether the patient has H. pylori infection or not, is a highly sensitive, specific, rapid, simple, safe and inexpensive Hp diagnostic method in the clinic. Subjects who have used HP inhibiting drugs, such as antibiotics, bismuth, etc., in the last month, or who have had a history of upper gastrointestinal bleeding in the last week, or who have food in their stomachs, and it is difficult to contact the gastric mucosa with the oral carbon 14 urea capsule, should be prohibited from doing the carbon 14 breath test. Pregnant and lactating women should try not to do this test. Carbon 14 breath test should be examined in a regular hospital and follow the doctor’s requirements so as not to affect the accuracy of the results.