Fasting is usually not required to check the hepatitis B half-pair. Hepatitis B 2.5 usually refers to the five hepatitis B tests. They are Hepatitis B surface antigen (HBsAg), Hepatitis B surface antibody (anti-HBs), Hepatitis B E antigen (HBeAg), Hepatitis B E antibody (anti-HBe), and Hepatitis B core antibody (anti-HBc). The results of these five tests can be used to initially determine if you have hepatitis B or if you have antibodies in your body. Fasting is not required if only doing the test of Hepatitis B two-to-half, and the results of the test will not be affected after eating and drinking, but it should be noted that fasting is required if the patient also needs to have liver function tests. It is recommended to consult a doctor before the test, and if hepatitis B is diagnosed, it is recommended to actively cooperate with the doctor for treatment.