What should you know about hepatitis B anti-HBsAg?

The terms in a hepatitis B report can be confusing. HBsAg is a surface-antigen marker, while anti-HBs is an antibody marker. They are not interchangeable, and one result alone may not show whether a person has current infection, past exposure, or vaccine-related immunity. The laboratory report may also include other markers that complete the picture. Your clinician will consider the pattern, symptoms, vaccination history, and any previous results. Learn more about [Hepatitis B](/conditions/hepatitis-b/).

Keep a copy of the complete report rather than relying on a single label. Tell the clinician when you received hepatitis B doses, whether you have had earlier testing, and whether you have fatigue, dark urine, yellowing of the eyes, or abdominal discomfort. They may repeat or add blood tests and may assess liver health with a [Liver Function Test](/treatments/diagnostics-and-screening/liver-function-test/). Do not diagnose yourself from an isolated positive or negative marker, and do not start treatment without a clinical review.

Arrange timely medical review if a report shows a hepatitis B marker that your clinician has not explained, especially during pregnancy or before a procedure. Seek urgent help for confusion, severe vomiting, significant bleeding, rapidly worsening jaundice, or fainting. Dark urine and fatigue are not specific to hepatitis B, but new or worsening symptoms deserve assessment.

Ask what each marker means, whether the pattern suggests current infection or immunity, whether more testing is needed, and whether close contacts should discuss [Hepatitis B Vaccination](/treatments/preventive-care-and-vaccination/hepatitis-b-vaccination/). Ask when to repeat testing and how the result affects work, pregnancy, or planned care.