Hepatitis B Surface Antibody (Anti-HBs)
Hepatitis B surface antibody (anti-HBs) is an antibody your immune system makes against the hepatitis B virus. This blood test measures whether you have developed these protective antibodies.
Anti-HBs is the antibody linked to immunity against hepatitis B. It usually appears after you recover from a past infection or after you complete the hepatitis B vaccine series. Checking for it helps confirm whether you are protected, which is especially useful after vaccination or when assessing risk in people who may have been exposed.
A positive (reactive) result generally means you are immune to hepatitis B, either because you recovered from a previous infection or because you responded to the vaccine. This is a reassuring result. To tell whether immunity came from vaccination or from past infection, your clinician looks at it together with other markers, such as the core antibody (anti-HBc).
A negative (non-reactive) result means you do not have detectable protective antibodies. This suggests you may not be immune, meaning you could be susceptible to hepatitis B. Your clinician may recommend vaccination or, if you were recently vaccinated, note that antibody levels can take time to build or may fade over the years.
A positive result is the desirable outcome here, because it usually indicates immunity. Laboratories often report a level above a set threshold as evidence of protection. Your clinician will interpret your result in the context of your vaccination history and any past exposure.
Sources
- Hepatitis B Blood Tests: MedlinePlus Medical Test
- Hepatitis B Questions and Answers for Health Professionals: CDC
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.