Before gastroscopy, blood tests are needed to prevent cross-infection and exclude coagulation abnormalities. 1. Prevent cross-infection: To do general gastroscopy, it is necessary to draw blood for infection and other related indexes, such as Hepatitis B V, syphilis, AIDS, Hepatitis C, etc., to make it clear whether the patient suffers from these infectious diseases, and if there are any of the above mentioned infectious diseases, corresponding treatments should be carried out during gastroscopy, so as to avoid cross-infection. 2. Rule out coagulation abnormalities: If gastroscopy also requires endoscopic treatment, such as histopathological biopsy or gastric polypectomy, etc., four coagulation tests are required before the examination to rule out coagulation abnormalities, so as to avoid hemorrhage caused by the operation. It is recommended to follow the doctor’s instructions to do a good job of preparation before gastroscopy, which is conducive to the smooth progress of gastroscopy.