The DOB value is an important indicator for detecting H. pylori infection in the carbon 13 breath test, which is a method to check H. pylori. In general, the normal range of DOB value in carbon 13 breath test is <4. When the DOB value of carbon 13 breath test is ≥4, it indicates the infection of H. pylori, and the larger the value, the more serious the infection. H. pylori is a special kind of bacteria that can persistently colonize the human gastric mucosa and cause mucosal infections, which can lead to gastritis, peptic ulcers, lymphoproliferative gastric lymphoma, gastric cancer and other diseases. Therefore, H. pylori infection should be taken seriously when it occurs. H. pylori contains a urease substance, and urease can decompose carbon 13-urea to produce carbon 13-CO2, which is absorbed by the digestive system and then excreted by the lungs. After taking carbon 13-urea reagent for 15 minutes, the presence of H. pylori infection can be known by testing whether carbon 13-CO2 is present in the exhaled gas. The carbon 13 breath test is not only simple and non-invasive, but complete exhalation is required during expiration in order to know the maximum value of carbon 13-carbon dioxide and to determine the severity of H. pylori infection. The normal range of DOB value of carbon 13 breath test is <4. Once the DOB value of carbon 13 breath test is ≥4, it indicates that the stomach is invaded by H. pylori, and the higher the value, the more serious it is and the need for timely treatment. Even if the DOB value is ≥4, patients should not be too alarmed because there are more patients infected with H. pylori who do not show more clinical symptoms. It is recommended to strictly follow medical advice on regular medication and regular review, and to ensure a regular life in daily life, avoiding overexertion and mental stress.