The Hepatitis B Surface Antibody (HBsAb) Test

Used to determine if you are immune to the hepatitis B virus

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The hepatitis B surface antibody test (HBsAb) detects proteins that are made by the immune system (antibodies) in response to the hepatitis B virus (HBV). The test is used to find out if you are immune to the virus after natural exposure or vaccination. You have to give a blood sample for the HBsAb test, which is checked in a lab.

A positive or "reactive" result on the HBsAb test means that you're immune to the hepatitis B virus. A negative or "non-reactive" result means that you're not immune to the virus.

This article explains what the hepatitis B surface antibody test is for, when it is used, and how the test is done. It also goes over what a positive and negative hepatitis B surface antibody test result can mean. 

An illustration with information about the hepatitis B surface antibody test

Illustration by Julie Bang for Verywell Health

Purpose of the Hepatitis B Surface Antibody Test

The HBsAb test looks for the presence and quantity of HBV antibodies in your blood. The test shows how immune you are to the virus. 

Antibodies are "encoded" by your immune system when your body is exposed to the HBV virus through blood or sexual contact, or if you are vaccinated with the hepatitis B vaccine. Your body can use the antibodies to attack the virus if it appears again.

There are two types of antibodies produced in response to the hepatitis B virus:

  • Immunoglobulin M (IgM) is the antibody that mounts the first attack against the virus but eventually fades away.
  • Immunoglobulin G (IgG) is the antibody that provides long-lasting immune protection against HBV. The immunity can last for many years, but it gradually decreases over time.

The HBsAb test can check for a previous exposure to HBV and tell how recent it was. By comparing levels of IgM and IgG, a healthcare provider can also use the test to monitor your recovery from an acute HBV infection.

The HBsAb test can also show whether your vaccine protection is good enough. Your test can indicate whether you are successfully vaccinated, not successfully vaccinated, or indeterminately vaccinated against hepatitis B. A booster vaccine might be needed if HBsAb level drops below protective levels.

The HBsAb test is not the same as the hepatitis B surface antigen (HBsAg) test or the hepatitis B core antibody (HBcAb) test. Those tests are used to determine if you have been infected with HBV.

Who Should Get Tested?

A hepatitis B surface antibody test is recommended for:

  • Infants born to people who may have hepatitis B
  • Workers who are likely to be exposed to blood and body fluids
  • People on kidney dialysis
  • Immunocompromised people
  • People who have a hepatitis B-positive partner

How the HBsAb Test Is Done

The HBsAb test is done by taking a blood sample that can be sent to the lab. Your healthcare provider will check the results against your vaccination history, symptoms, and exposure risk, as well as the results of other hepatitis tests.

Interpreting Results

Your HBsAb test result can be positive or negative, but how your provider interprets the results will depend on what the other tests (HBsAg and HBcAb) showed. 

Positive

If your HBsAb result is positive or "reactive"—meaning the surface antibodies are present—it usually means that you have recovered from a recent or previous hepatitis B infection and that you are immune to the virus. If both the HBsAb and HBcAb are positive, you are said to be immune due to natural infection.

If you received the hepatitis B vaccine, a positive HBsAb result on its own also shows that you’re immune.

Negative

An HBsAb test that is negative or "non-reactive" can mean different things. In general, it means that you are not immune to the virus.

There are several ways to interpret HBsAb test results based on the results of the other hepatitis B tests.

Test   Result  Interpretation
HBsAb
HBsAg
HBcAb
Negative
Negative
Negative
Not infected
HBsAb
HBsAg
HBcAb
IgM Positive
IgG Negative
Negative
Acute (recent) infection
HBsAb
HBsAg
HBcAb
Negative
Positive
Positive
Chronic (ongoing) infection
HBsAb
HBsAg
HBcAb
Negative
Negative
Positive
Three possibilities:
1. Resolved infection
2. False positive
3. Low-level chronic infection

Follow-Up

If your HBsAb is positive, you cannot infect others and do not need vaccination.

If all three tests are negative—meaning that you have never been exposed to the virus—you will be advised to get the HBV vaccine.

If your HBsAb test is negative but the other tests are positive, your healthcare provider will need to evaluate you further. Whether your infection is acute or chronic, you still have the ability to infect others and need to take steps to avoid spreading the virus. 

If the results are unclear, all three tests will be repeated.

Treatment

If your hepatitis B surface antibody test is positive, your provider will look at your other blood tests to determine whether you need treatment.

Medications that can treat hepatitis B include:

  • Immune modulators: These medications help your immune system get rid of hepatitis B. You have to take shots of the medication, usually for six months to up to a year. 
  • Antivirals: These are medications you can take by mouth that help your body clear the hepatitis virus. You will probably need to take the pills every day for at least a year, if not longer. 

Summary

The hepatitis B surface antibody (HBsAb) test detects and measures antibodies made by the immune system in response to the hepatitis B virus. It is one of the tests used to diagnose hepatitis B and specifically shows how immune you are to the virus. 

You need to have blood taken for the test. A positive result usually means that you are immune to the virus and cannot infect others. A negative result has to be considered along with the results of the other tests.

If all of your hepatitis tests are negative, it indicates that you have not been exposed to the virus and are not immune. If this is the case, talk to your healthcare provider about getting vaccinated—whether or not you are at risk of hepatitis B. Even if you are immune to hepatitis B, you may still be at risk for other types of hepatitis, including hepatitis C.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Song JE, Kim DY. Diagnosis of hepatitis B. Ann Transl Med. 2016;4(18):338. doi:10.21037/atm.2016.09.11

  2. Hepatitis B Foundation. Vaccination.

  3. Immunization Action Coalition. Hepatitis B.

  4. Centers for Disease Control and Prevention. Interpretation of Hepatitis B Serologic Test Results.

  5. The Hepatitis Foundation of New Zealand. Understanding your results.

  6. Hepatitis B Foundation. Treatment and management.

Additional Reading

By Charles Daniel
 Charles Daniel, MPH, CHES is an infectious disease epidemiologist, specializing in hepatitis.