Disclosed herein is the use a cyanobacterial biomass for treating hepatitis B virus (HBV) infection, in particular, chronic HBV infection. According to various embodiments of the present disclosure, the cyanobacterial biomass, upon administration of at least one month, significantly reduces the level of the surface antigen of hepatitis B virus (HBsAg) detectable in the subject receiving the treatment and/or mitigates insomnia associated with chronic HBV infection.
