Normally, hepatitis B virus carriers do not require any treatment. However, when the body’s immunity is severely suppressed, hepatitis B virus carriers may also experience varying degrees of hepatitis B reactivation, which may develop into acute liver failure or even lead to death in severe cases. Chemotherapy for tumors or immunosuppressive therapy for autoimmune diseases are the most common causes. Therefore, all hepatitis B virus carriers receiving chemotherapy or immunosuppressive therapy for other diseases should be routinely screened for HBsAg, anti-HBc and HBV DNA before chemotherapy and assessed for the degree of risk of hepatitis B reactivation. For patients at higher risk of hepatitis B reactivation, antiviral therapy should be started 1 week before starting immunosuppressive and chemotherapeutic drugs and should not be considered for discontinuation until 6 months after cessation of chemotherapy or immunosuppressive therapy. In conclusion, if a hepatitis B carrier needs chemotherapy or immunosuppressive therapy, it is important to inform your doctor of your liver disease and remind him or her not to forget to assess the risk of hepatitis B reactivation.