What should you know about hepatitis B core antigen?

The core antigen itself is usually not the routine item reported on a blood test. Instead, the test looks for antibodies to it. A positive core antibody can show that your immune system has encountered hepatitis B, but it does not by itself tell whether infection is current, past, or resolving. Clinicians compare it with surface antigen, surface antibody, and sometimes hepatitis B DNA. This pattern helps distinguish immunity after vaccination from immunity after infection. Read more about [Hepatitis B](/conditions/hepatitis-b/).

Take the complete result to a clinician rather than interpreting one marker alone. Ask whether the panel suggests current infection, previous exposure, or susceptibility. Further blood work may include a [Liver Function Test](/treatments/diagnostics-and-screening/liver-function-test/) and a viral DNA test. Until the pattern is clear, avoid sharing razors or toothbrushes and discuss household or sexual contacts with a clinician. If you are not immune, ask about [Hepatitis B Vaccination](/treatments/preventive-care-and-vaccination/hepatitis-b-vaccination/).

Arrange medical review promptly if a result suggests current infection, especially with yellowing of the skin, vomiting, marked tiredness, abdominal pain, or [Dark Urine](/symptoms/dark-urine/). Seek urgent help for confusion, severe weakness, bleeding, or inability to keep fluids down. Mild or absent symptoms do not settle the meaning of a core antibody result; follow-up testing remains necessary.

Ask: Which hepatitis B markers were tested? Does this pattern show current infection or previous exposure? Do I need repeat testing or a hepatitis B DNA test? Should my liver function be checked? Who should be tested or vaccinated at home?