Hepatitis B is a liver disease caused by infection with the hepatitis B virus (HBV). The liver becomes swollen and tender (inflamed) and may develop permanent damage, such as scarring or liver cancer.

The hepatitis B virus spreads by way of body fluids, including blood, semen, and vaginal fluids (including menstrual blood).

The infection can be short-term (acute) or long-term (chronic) and may cause flu-like symptoms, such as extreme tiredness, fever, headache, nausea and vomiting, diarrhea (or constipation), and muscle aches. Other symptoms may include discomfort under the right rib cage, joint pain, skin rash, and yellowing of the skin and eyes (jaundice).

Acute hepatitis B usually goes away on its own; home treatment is used to relieve symptoms and help prevent spread of the virus. Treatment for chronic HBV infection includes monitoring the condition and using antiviral medicines to prevent liver damage. If hepatitis B has caused severe liver damage, a liver transplant may be needed.

Hepatitis B can be prevented by vaccination.