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Blood Test Tracker

Hepatitis B Surface Antibody (Anti-HBs)

The antibody that protects against hepatitis B. A result of 10 mIU/mL or higher is generally treated as protected, from vaccination or past infection.

AI-verified against cited sources. Awaiting expert reviewAlso called Anti-HBs, HBsAb, HBs AbLOINC 5193-8

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What it is

Anti-HBs (hepatitis B surface antibody) is made by your immune system after hepatitis B vaccination or after you recover from a hepatitis B infection. It helps protect you if you are exposed to the virus. Many labs report the amount in mIU/mL, and some only print reactive or non-reactive. Public health guidance treats 10 mIU/mL or more as protective.

Why it matters

This test shows whether you are likely protected against hepatitis B. It's often checked 1 to 2 months after the last vaccine dose in people who need proof of protection, such as health care workers, people on dialysis, people with HIV or other immune conditions, sexual partners of people with hepatitis B, and infants born to mothers with hepatitis B (ACIP 2018). It's also one of the three tests in the standard hepatitis B panel. A low result alone doesn't mean illness. It means no protective antibody was found.

If it’s low

A result below 10 mIU/mL means no protective antibody was detected. Many unvaccinated people have this result, and it is not a sign of illness. If you were vaccinated, it can mean the antibody level has faded over time or that you did not respond to the series. Your clinician can tell you whether vaccination or revaccination makes sense.

Common causes

  • Never vaccinated and never infected
  • Antibody level that has faded since vaccination
  • A weaker response to the vaccine, which is more common with older age, smoking, obesity, diabetes, other long-term illness and a weakened immune system (ACIP 2018)
  • Kidney failure or dialysis, or other conditions that weaken the immune system

What can help

  • Ask your clinician whether hepatitis B vaccination, or revaccination if you were vaccinated before, is right for you
  • Ask whether you need a repeat antibody test after vaccination, and when
  • If you were fully vaccinated and your immune system is healthy, ask whether any action is needed. The CDC does not generally recommend booster doses for these people

If it’s high

A level of 10 mIU/mL or higher means protective antibody is present. A higher number generally means a stronger response right now, but there's no need to chase a specific higher number. Antibody levels often fall over the years after vaccination, and the CDC notes that most people who finished the series stay protected.

Common causes

  • Successful hepatitis B vaccination
  • Recovery from a past hepatitis B infection (usually with a positive total anti-HBc)
  • Recent hepatitis B immune globulin, which gives temporary antibody for about 4 to 6 months

What can help

  • If you need proof of protection for work, school or travel, keep a copy of this report with your vaccine records
  • Ask your clinician whether your other hepatitis B results show the protection comes from vaccination or from a past infection

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

For adults: 10 and above mIU/mL. Source: Mayo Clinic Laboratories (Extended Catalog), CDC, MMWR Recommendations and Reports (CDC).

If this applies to you

Anti-HBs means a little more for some people. Open the one that fits you.

Taking HIV PrEP

Anti-HBs shows protection against hepatitis B. The CDC guideline says people on PrEP who aren't immune and don't have hepatitis B should be offered the vaccine.

Blood tests on HIV PrEP

What can affect your result

  • Age: vaccine response is weaker in older adults
  • Smoking, obesity, diabetes, male sex, long-term illness and a weakened immune system are linked to a weaker response (ACIP 2018)
  • Time since the last dose: levels often decline over the years, but most people stay protected (CDC)
  • Recent hepatitis B immune globulin gives temporary antibody for about 4 to 6 months
  • Assay brand: cutoffs and equivocal zones differ between labs
  • Biotin supplements can interfere with some immunoassays
  • Mayo Clinic Laboratories asks patients to avoid biotin (vitamin B7) supplements for 24 hours before its anti-HBs test.
  • Hepatitis B immune globulin (HBIG) gives temporary antibody that can be detected for about 4 to 6 months (ACIP 2018).
  • Assay brands use different cutoffs, and some print an equivocal zone near the cutoff.

Antibody builds in the weeks after the last vaccine dose. CDC/ACIP suggest checking 1 to 2 months after the final dose when a check is needed. Levels often fall over the years.

When to talk to a clinician

A low anti-HBs result isn't urgent. Talk with a clinician if you work in health care, are pregnant, are on dialysis, live with someone who has hepatitis B, or have a weakened immune system, since vaccination or retesting may matter more for you. If you may have been exposed to hepatitis B and are not sure you are protected, contact a clinician or urgent care promptly, because time-sensitive preventive treatment may be available.

Questions you could ask

  • Do I have a record of my hepatitis B vaccine series?
  • Do my other hepatitis B results show this protection comes from vaccination or from a past infection?
  • Do I need hepatitis B vaccination or revaccination?
  • Should this test be repeated after vaccination, and when?
  • Do my job, health conditions or travel plans make this result more important?

Questions people ask

What number means I am immune?

A level of 10 mIU/mL or higher is generally treated as protective (CDC and ACIP). Some labs print this as reactive or immune. Below 10 means no protective antibody was detected.

My result is lower than last time. Did I lose protection?

Antibody levels often fall over the years after vaccination. The CDC notes that most people who completed the series stay protected even when levels drop, because the immune system remembers. Ask your clinician whether anything is needed in your situation.

Can a positive anti-HBs come from an infection instead of the vaccine?

Yes. After you recover from hepatitis B, anti-HBs is positive too, along with anti-HBc. Vaccination causes only anti-HBs. Your other hepatitis B results show which applies.

Show the science and sources

Units

  • 1 mIU/mL = 1 mIU/mL
  • 1 mIU/mL = 1 IU/L

For clinicians and researchers

Anti-HBs is the neutralizing antibody to HBsAg. ACIP and CDC define seroprotection as 10 mIU/mL or higher, measured 1 to 2 months after the last vaccine dose. Vaccination produces anti-HBs without anti-HBc, while natural recovery produces both (ACIP 2018). Levels wane after vaccination, but immune memory persists. In the ACIP review, 88% of people given a challenge dose 30 years after vaccination developed an antibody response of at least 10 mIU/mL. People below 10 mIU/mL after a primary series are revaccinated and retested 1 to 2 months after the final dose. Passively acquired anti-HBs from HBIG is detectable for 4 to 6 months. Mayo Clinic Laboratories uses an electrochemiluminescence immunoassay and reports quantitative results with 10.0 mIU/mL as the dividing line (below 10.0 expected for unvaccinated people, 10.0 or higher for vaccinated people). 1 mIU/mL is equal to 1 IU/L. In chronic hepatitis B, loss of HBsAg with gain of anti-HBs is called functional cure (AASLD 2018).

LOINC 5193-8 (primary), 16935-9, 10900-9, 22322-2. Specimen: serum-or-plasma.

Sources

  1. Hepatitis B Virus Surface Antibody Screen, Qualitative/Quantitative, Serum (test HBBSN), Mayo Clinic Laboratories (Extended Catalog)
  2. Clinical Testing and Diagnosis for Hepatitis B, CDC
  3. Screening and Testing for Hepatitis B Virus Infection: CDC Recommendations — United States, 2023, MMWR Recommendations and Reports (CDC) (2023)
  4. Prevention of Hepatitis B Virus Infection in the United States: Recommendations of the Advisory Committee on Immunization Practices, MMWR Recommendations and Reports (CDC) (2018)
  5. Update on Prevention, Diagnosis, and Treatment of Chronic Hepatitis B: AASLD 2018 Hepatitis B Guidance, Hepatology (AASLD) (2018)
  6. Understanding Your Hepatitis B Test Results, Hepatitis B Foundation

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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