An electrocardiogram (ECG), blood tests, and tests for infectious diseases may be required before the gastroscopy. 1. Electrocardiogram (ECG): This is usually a mandatory test before all tests to see if there are any problems with the heart. If there are problems with the heart, such as atrioventricular (AV) block, it is usually not suitable for a gastroscopy. 2. Blood test: It is mainly done by drawing blood to see if the hemoglobin and platelets are within the normal range. If the hemoglobin or platelets are too low, serious bleeding can easily occur during the examination. 3. Infectious disease test: mainly to check whether there are infectious diseases such as Hepatitis B, AIDS, etc., to avoid transmission because of the blood system. In addition, before doing gastroscopy, you must be clear about whether you have contraindications, and you should consult your doctor for details.