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Hepatitis B surface antigen

Infection and immunity tests · also printed as HBsAg, HBs Ag, Hep B surface antigen, Hepatitis B sAg, Hep B sAg

Typical UK adult rangeExpected result: Negative

Negative is the expected result.

What this test measures

Hepatitis B surface antigen is a protein from the outer coat of the hepatitis B virus. Finding it in blood means the virus is present now, whether as a recent or a long-standing infection.

Why doctors request it

Part of hepatitis screening in pregnancy, before some medicines, after possible exposure, and in liver tests.

What commonly pushes it up

Current hepatitis B infection, recent or long-standing
In the two weeks after a hepatitis B vaccine, a transient weak positive can occur

What commonly pushes it down

A negative result is the usual finding

Everyday reasons for a value outside the range

Results can be equivocal and are then repeated
Recent vaccination or infection elsewhere can occasionally give a weak positive

About the sample

No fasting needed.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.

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This is an educational summary of results you uploaded. It is not medical advice, a diagnosis or a treatment plan, and it does not replace the doctor who requested the test. If you are worried, or a result is marked outside range, discuss it with your doctor. Written and reviewed by a UK consultant physician. Reference ranges vary between laboratories.