Hepatitis B surface antigen (HBsAg) is one of the five hepatitis B pathogenic tests (hepatitis B five), and the significance of its negativity needs to be specifically analyzed in conjunction with the other four. Hepatitis B surface antigen can appear in the blood 2 weeks after infection with hepatitis B virus (HBV), reflecting current hepatitis B virus infection, and can persist for years, even for life, in asymptomatic carriers and chronic patients. Hepatitis B surface antigen itself is only antigenic and not infectious. However, negative cannot exclude hepatitis B virus infection, such as patients infected with hepatitis B virus, due to the short period of time, hepatitis B surface antigen has not yet manifested, etc., so the specific also need to comprehensive analysis. If all five hepatitis B items are negative, it means that the patient is not infected with hepatitis B virus and there is no antibody to hepatitis B virus in the body. In this case, it is recommended that the patient be vaccinated against hepatitis B to prevent infection; if the hepatitis B surface antigen is negative and the hepatitis B surface antibody (anti-HBs) is positive, it means that there is protective antibody in the body and there is immunity to hepatitis B virus. This may be the case if you have received the hepatitis B vaccine or if you have been infected with the hepatitis B virus but have recovered and developed antibodies. Therefore, a negative hepatitis B surface antigen generally means that the patient is not infected with the hepatitis B virus, but it cannot be completely ruled out, and the specific situation needs to be analyzed in conjunction with several other items.