The 13C breath test, also known as the urea breath test, is normal with a result of 4 or less. A result of 4 or less is considered normal. Above this value, the presence of Helicobacter pylori infection in the stomach is possible. The urea breath test is used to detect the presence of H. pylori infection in the stomach and is non-invasive, highly specific and quick. The presence of H. pylori infection is determined by measuring the ratio of 13C/12C concentration in exhaled CO2 before and after drug administration. A cut-off value of 4.0 above baseline is usually used, with 4.0 and above being considered H. pylori positive and 4.0 and below being considered H. pylori negative. When using C13 for the urea breath test, remain sedentary after taking the medication, fast, abstain from smoking, and avoid strenuous activity. Fasting for at least 6 hours before the test and discontinuing antibiotics for at least 4 weeks before the test are necessary to avoid false-negative results. The 13C breath test is not recommended in cases of acute upper gastrointestinal bleeding or previous gastrectomy. Helicobacter pylori infection is closely related to the development of many digestive diseases and is the most important and controllable risk for the prevention of gastric cancer. If an abnormal level of this test is present, it is recommended to visit a hospital for prompt treatment.