When a patient develops H. pylori infection it can be determined by a blood test. H. pylori is usually parasitized in the stomach and can cause a series of gastrointestinal diseases such as gastric ulcers, gastritis, duodenal ulcers, and gastric cancer when patients are infected. Most of the infected people do not have symptoms. At the onset of the disease, abdominal pain, bloating, loss of appetite, acid reflux, nausea and other symptoms may occur. Patients can be tested for H. pylori through blood tests. Commonly used methods include serological antibody tests, which mainly test the sensitivity and specificity of H. pylori antibodies to determine whether the patient is infected or not, but it is not possible to determine whether the patient is currently infected or previously infected. In addition, patients can also be diagnosed by carbon 13, carbon 14 breath test, fecal antigen test, etc. Patients who are diagnosed should be treated promptly.