Hepatitis B Test (HBsAg)
A blood test that checks for hepatitis B infection.
Quick Summary
To diagnose hepatitis B, screen in pregnancy and before treatments, and check immunity.
HBsAg (infection), anti-HBs (immunity) and other markers.
No preparation needed.
Overview
HBsAg positive means current infection.
Anti-HBs shows immunity from vaccination or past infection.
What It Measures
HBsAg
Current infection.
Anti-HBs
Immunity.
HBV DNA
Amount of virus, if infected.
How It's Performed
- 01
Preparation
Usually no special preparation. Tell the staff about medicines you take.
- 02
Blood sample
A small amount of blood is taken from a vein in your arm with a thin needle.
- 03
Afterwards
Press on the spot for a minute. A small bruise is common; you can go back to normal activities.
Interpreting Results & Next Steps
Discuss with Doctor
Normal ranges differ between laboratories, ages and sexes; always use the range printed on your report and ask your doctor what your results mean.
If values are High:
A positive HBsAg needs further tests and follow-up.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Hepatitis Testing(opens in a new tab) · MedlinePlus, US National Library of Medicine