Lab result explainedInflammationLast updated November 11, 2026

Hepatitis B surface antigen (HBsAg): what positive and reactive results, and the full hepatitis B panel, mean

Hepatitis B surface antigen (HBsAg) · Hepatitis B panel: surface antigen (HBsAg), surface antibody (anti-HBs), total core antibody (anti-HBc) · reported in HBsAg: reactive (positive) or non-reactive (negative); quantitative HBsAg and HBV DNA in IU/mL; anti-HBs in mIU/mL

Hepatitis B surface antigen (HBsAg) is a protein from the outer coat of the hepatitis B virus. Finding it in your blood means the virus is present and multiplying in your liver right now, so a positive (reactive) HBsAg is the defining test for current hepatitis B infection. It appears within 1 to 9 weeks of exposure (typically about 4), before any symptoms, and in people who recover it disappears within about 6 months. If it is still present after 6 months, the infection is chronic, which happens in about 90 percent of people infected at birth, 25 to 50 percent of those infected as young children, and fewer than 5 percent of those infected as adults.

HBsAg is almost always reported alongside two other tests that together make up the hepatitis B panel. Hepatitis B surface antibody (anti-HBs) is the protective antibody produced by vaccination or recovery. Hepatitis B core antibody (anti-HBc) is made only in response to real infection, never to the vaccine, and persists for life, so it tells you whether the virus has ever been in your body. Read as a set, the three sort nearly everyone into one of a handful of patterns: currently infected, immune from vaccination, immune from a past infection, never exposed, or an unusual pattern that needs a closer look. Further tests (IgM core antibody, e antigen, HBV DNA, liver enzymes) refine the picture once HBsAg is positive.

Between 580,000 and 2.4 million people in the United States live with chronic hepatitis B, and about two thirds do not know it, because the infection is silent for decades while it can quietly cause cirrhosis and liver cancer. Since 2023 the CDC has recommended that every adult be tested with the full panel at least once, that every pregnant person be tested for HBsAg in each pregnancy, and that people born in regions where hepatitis B is common, and other higher-risk groups, be tested regardless of symptoms. A positive HBsAg is not a dead end: antiviral tablets suppress the virus very effectively, regular monitoring catches liver cancer early, and household and sexual contacts can be fully protected by vaccination.

HBsAg at a glance

  • What it is: a blood test for the surface coat protein of the hepatitis B virus; positive means current infection, reported with surface antibody and core antibody as the hepatitis B panel.
  • HBsAg negative (non-reactive): no current infection. The other two tests then show whether you are immune (vaccinated or recovered) or susceptible and should be vaccinated.
  • HBsAg positive for under 6 months with a positive IgM core antibody: acute hepatitis B; most adults clear it. Positive for more than 6 months: chronic hepatitis B.
  • Core antibody positive, HBsAg negative, surface antibody positive: past infection, resolved and immune. Core antibody positive on its own: usually a distant resolved infection, occasionally a false positive or low-level infection.
  • A positive HBsAg within 2 to 3 weeks of a hepatitis B vaccine dose can be a harmless false positive from vaccine antigen; retest later.
  • Next step for a positive HBsAg: HBV DNA, e antigen/antibody, ALT, platelets, hepatitis D, HIV and hepatitis C tests, a liver ultrasound in many cases, and a plan for monitoring or antiviral treatment; vaccinate household and sexual contacts.

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What HBsAg measures

The hepatitis B virus makes far more surface protein than it needs for its own coat, releasing the excess into the blood as empty spheres and filaments; concentrations can reach hundreds of thousands of international units per milliliter. The HBsAg immunoassay captures this protein with antibodies and reports it as reactive or non-reactive relative to a cutoff. Because it is so abundant, HBsAg is detectable 1 to 9 weeks after exposure, several weeks before liver enzymes rise or symptoms begin, and 30 to 60 days before jaundice in those who develop it. Low-level reactive results are confirmed by a neutralization step, in which adding anti-HBs antibody should abolish the signal if it is genuine.

Quantitative HBsAg (qHBsAg, in IU/mL) is used in specialist monitoring of chronic infection: levels below 1,000 IU/mL together with HBV DNA below 2,000 IU/mL identify people in a stable inactive phase who are at low risk of progression, and a steady fall in HBsAg predicts eventual loss of the antigen, the closest thing to a resolution of chronic hepatitis B, which occurs spontaneously in about 1 percent of carriers a year. The other panel tests measure your response to the virus: total anti-HBc (IgG plus IgM) appears at the onset of symptoms and persists for life, IgM anti-HBc marks infection within the past 6 months, and anti-HBs appears as HBsAg disappears in recovery, or after vaccination.

Once HBsAg is positive, e antigen (HBeAg) and HBV DNA measure how actively the virus is replicating. HBeAg-positive infection usually comes with DNA levels in the millions of IU/mL and is the most infectious state; loss of HBeAg and gain of anti-HBe typically marks a shift to lower replication, although some strains keep replicating without making HBeAg. ALT shows whether the immune system is currently attacking infected liver cells. Treatment decisions rest on HBV DNA, ALT, the degree of fibrosis and family history rather than on HBsAg alone, and the natural history moves through phases over decades, which is why monitoring every 6 to 12 months continues for life even when no treatment is needed.

Normal range for HBsAg

Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.

GroupTypical range (HBsAg: reactive (positive) or non-reactive (negative); quantitative HBsAg and HBV DNA in IU/mL; anti-HBs in mIU/mL)Notes
HBsAg non-reactive (negative)Below the assay cutoffNo current infection (with rare exceptions: the window period of acute infection and occult infection, both flagged by a positive core antibody). Surface and core antibody results then define immunity.
Acute hepatitis BHBsAg reactive, IgM anti-HBc positive, anti-HBs negative; HBV DNA usually high; ALT often above 500 U/LWithin 6 months of exposure. About 95 percent of adults clear the virus; under 1 percent develop acute liver failure. Symptoms, when present, start 60 to 150 days after exposure.
Chronic hepatitis BHBsAg reactive on two tests more than 6 months apart; total anti-HBc positive, IgM negative; anti-HBs negativeLifelong infection in most. Phases are defined by HBeAg status, HBV DNA and ALT, and move over time, so monitoring every 6 to 12 months is lifelong.
HBeAg positiveHBV DNA typically above 20,000 IU/mL, often in the millionsHigh replication and highest infectivity. In people infected at birth this 'immune-tolerant' phase can last into the 30s with normal ALT.
HBV DNA thresholds used in decisionsUnder 2,000 IU/mL with normal ALT: inactive phase; above 2,000 with raised ALT or fibrosis: treatment considered; above 200,000 in pregnancy: antiviral from 28 weeks to protect the babyAntiviral treatment (tenofovir or entecavir) aims for undetectable DNA. 1 IU/mL is roughly 5 copies/mL on older reports.
Quantitative HBsAgBelow 1,000 IU/mL with HBV DNA below 2,000 IU/mL: stable inactive carrier; above 1,000: higher risk of later activityBest validated in genotype D and used mainly by specialists. Falling levels predict eventual HBsAg loss.
Resolved past infection (pattern)HBsAg negative, total anti-HBc positive, anti-HBs positiveRecovered and immune. The virus persists in a dormant form in liver cells and can reactivate under strong immunosuppression, so this pattern is screened for before chemotherapy, rituximab and transplant.
Immune from vaccination (pattern)HBsAg negative, anti-HBc negative, anti-HBs 10 mIU/mL or moreVaccines never produce core antibody. Anti-HBs may fall below 10 years later while immune memory persists.
Isolated core antibody (pattern)HBsAg negative, anti-HBc positive, anti-HBs negativeMost often a distant resolved infection with lost surface antibody; also a false-positive core antibody, the window period of acute infection, or low-level occult infection. HBV DNA and a repeat panel, or a vaccine dose with a follow-up anti-HBs, clarify.

Positive (reactive) hepatitis B surface antigen

A positive HBsAg means hepatitis B virus is in your body now. The first question is whether this is a new infection or a long-standing one, and the IgM core antibody answers it: positive IgM anti-HBc means infection within the past 6 months (acute hepatitis B), while a positive total core antibody with negative IgM means the infection is older. Most adults with acute hepatitis B recover completely over 2 to 4 months, with HBsAg disappearing and protective surface antibody appearing; they need rest, avoidance of alcohol and liver-toxic drugs, monitoring of liver function, and urgent review if they become confused or drowsy, since about 0.5 to 1 percent develop acute liver failure. Antiviral treatment is reserved for severe acute cases.

HBsAg that remains positive on a repeat test more than 6 months later means chronic hepatitis B. For most people in the United States with this result, the infection was acquired at birth or in early childhood, often in a country where hepatitis B is common (much of Asia, sub-Saharan Africa, the Pacific Islands, parts of Eastern Europe and South America), and it has been silent ever since. Chronic infection moves through phases defined by HBV DNA, e antigen and ALT, and the risks it carries, cirrhosis in 15 to 40 percent over a lifetime and liver cancer even without cirrhosis, depend on those phases. Many people need only monitoring every 6 to 12 months; others benefit from daily antiviral tablets (tenofovir or entecavir) that suppress the virus to undetectable levels, halt fibrosis and reduce the risk of liver cancer by about half, although they rarely eliminate HBsAg and are usually long-term.

Two practical consequences follow from any positive HBsAg. You can transmit the virus through blood, semen and vaginal fluid, and from mother to baby at birth, so sexual partners and household members should be tested and, if not immune, vaccinated (the vaccine is highly effective and makes transmission within families preventable); you should not share razors, toothbrushes or needles, or donate blood, organs or semen. And you should tell every clinician who treats you, because chemotherapy, rituximab, high-dose steroids, biologic drugs and transplant immunosuppression can trigger a dangerous flare of hepatitis B unless preventive antiviral treatment is given, and because hepatitis B changes how other liver conditions and some medicines are managed. In pregnancy, a positive HBsAg leads to HBV DNA testing, antiviral treatment in the third trimester if the DNA is above 200,000 IU/mL, and vaccine plus hepatitis B immune globulin for the baby within 12 hours of birth, which together prevent transmission in more than 95 percent of cases.

Common causes

  1. Chronic infection acquired at birth or in early childhood

    The most common reason worldwide and among people born in regions with high hepatitis B prevalence. Infection in infancy becomes chronic about 90 percent of the time, and most people have no symptoms for decades.

  2. Acute infection acquired as an adult

    Through sex with an infected partner (the commonest adult route in the US), shared injection equipment, needlestick injuries, unsterile tattooing or piercing, or sharing razors and toothbrushes within a household. Fewer than 5 percent of adults develop chronic infection.

  3. Household or sexual contact of a person with hepatitis B

    Hepatitis B is 50 to 100 times more infectious than HIV through blood, and the virus survives on surfaces for at least 7 days. Unvaccinated contacts have a high lifetime risk of acquiring it, which is why testing and vaccination of contacts is standard.

  4. Recent hepatitis B vaccination (transient false positive)

    The vaccine contains purified surface antigen, which can be detected in blood for up to 2 to 3 weeks after a dose (longer in newborns and dialysis patients). Core antibody is negative and a repeat test a few weeks later is non-reactive.

  5. Reactivation of resolved or occult hepatitis B

    Chemotherapy, rituximab and other B-cell-depleting drugs, high-dose steroids, biologics, hepatitis C antiviral treatment and transplant immunosuppression can reawaken dormant virus in people with a positive core antibody, with HBsAg reappearing and sometimes severe hepatitis. Screening before these treatments is standard.

  6. Low-level or false-positive reactive signal

    Automated assays occasionally give a weak reactive result that fails the confirmatory neutralization test, particularly in people with autoimmune disease or after certain infections. Labs report these as 'unconfirmed' and a repeat panel, with HBV DNA if needed, settles it.

  7. Exposure before blood-product screening or in healthcare settings abroad

    Transfusion before 1972 in the US, unsterile medical or dental equipment and traditional practices in some countries, and long-term hemodialysis in the past account for many older chronic infections.

  8. Coinfection with hepatitis D

    Hepatitis D (delta) virus can only infect people who are HBsAg positive. It accelerates liver damage and is tested for (anti-HDV) in everyone with a new positive HBsAg under current guidance, especially people from Mongolia, Eastern Europe, Central Asia, parts of Africa and the Amazon basin, and people who inject drugs.

Symptoms that can go with it

  • Usually none; most chronic hepatitis B is discovered on screening, pregnancy testing or blood donation
  • Fatigue, loss of appetite, nausea, low-grade fever and aching joints in the weeks before jaundice in acute infection
  • Yellow skin and eyes, dark urine and pale stools, with tenderness under the right ribs, in about 30 to 50 percent of adults with acute infection
  • A transient itchy hive-like rash or joint pains before the hepatitis begins (serum-sickness-like syndrome)
  • Confusion, unusual sleepiness or easy bleeding during acute hepatitis, which signal liver failure and need emergency care
  • Over years: easy bruising, swollen ankles or abdomen, muscle wasting, red palms and spider-like blood vessels as cirrhosis develops
  • Unexplained weight loss, a new ache under the right ribs or a feeling of fullness, which prompt an urgent check for liver cancer
  • Kidney inflammation (protein in the urine, swelling) or a vasculitis rash, which are uncommon immune complications of chronic infection

Negative (non-reactive) hepatitis B surface antigen

A non-reactive HBsAg means no hepatitis B surface antigen was detected, and for almost everyone that means no current infection. What it does not tell you is whether you are protected. That comes from the other two panel tests: a positive surface antibody (10 mIU/mL or more) means you are immune, and the core antibody shows whether that immunity came from vaccination (core negative) or from a past infection you recovered from (core positive). If all three are negative you have never been infected and are not immune, and the CDC recommends vaccination for all adults aged 19 to 59 and for older adults with any risk factor.

There are three uncommon situations in which a negative HBsAg coexists with hepatitis B virus in the body. In the window period of acute infection, HBsAg has already disappeared but surface antibody has not yet appeared, so IgM core antibody is the only positive test for several weeks. In occult hepatitis B, HBsAg is undetectable but low levels of HBV DNA persist in the liver and sometimes the blood, usually in people with an isolated positive core antibody; this matters for blood donation, for liver transplant donors and recipients, and above all before immunosuppressive treatment, when the virus can reactivate. And rarely, mutations in the surface gene produce an antigen that some assays fail to detect, which is one reason core antibody and HBV DNA are added when the picture does not add up.

A negative HBsAg also does not exclude a very recent exposure: the antigen takes 1 to 9 weeks to appear. After a needlestick, sexual exposure or birth to an infected mother, the standard response is hepatitis B immune globulin and vaccination within 24 hours (12 hours for newborns) rather than waiting for a test, followed by testing at 1 to 2 months and again at 6 months. In someone with a known positive core antibody, a negative HBsAg plus a negative or low surface antibody is the pattern that triggers preventive antiviral treatment before rituximab, chemotherapy or transplant.

Common causes

  1. Never infected

    The expected result in most US adults. With negative core and surface antibodies you are susceptible and should be vaccinated; with a positive surface antibody and negative core antibody you are immune from vaccination.

  2. Resolved past infection

    HBsAg clears within 6 months in about 95 percent of infected adults, leaving a positive core antibody and, usually, a positive surface antibody. The person is immune, not infectious and has no ongoing liver injury, but carries dormant virus that can reactivate under strong immunosuppression.

  3. Window period of acute infection

    For a few weeks between the disappearance of HBsAg and the appearance of anti-HBs, IgM core antibody is the only positive result. Repeating the panel in 1 to 3 months shows surface antibody emerging.

  4. Occult hepatitis B

    HBsAg negative with detectable HBV DNA, nearly always with a positive core antibody. Found in about 1 to 5 percent of people with isolated core antibody in low-prevalence countries, more in high-prevalence regions and in people with HIV or hepatitis C.

  5. Too early after exposure

    HBsAg appears 1 to 9 weeks after exposure. A negative test within the first month of a known exposure needs repeating; post-exposure immune globulin and vaccination are given without waiting.

  6. Surface-gene variants not detected by the assay

    Vaccine-escape and diagnostic-escape mutants (for example at amino acid 145 of the surface protein) can be missed by some older assays. Suspected when core antibody and HBV DNA are positive despite a negative HBsAg; modern assays detect most variants.

Symptoms that can go with it

  • None; a negative HBsAg causes no symptoms
  • Fatigue, nausea, dark urine or jaundice within 1 to 6 months of a possible exposure should prompt a repeat panel with IgM core antibody and HBV DNA even if HBsAg was negative earlier
  • In someone with a positive core antibody who starts chemotherapy or rituximab, new fatigue, jaundice or rising ALT needs same-week review for reactivation

Read it alongside

  • Hepatitis B surface antibody (anti-HBs) — the marker of immunity; 10 mIU/mL or more is protective. Negative in nearly all people with a positive HBsAg.
  • Total hepatitis B core antibody (anti-HBc) — positive in anyone ever infected, never after vaccination alone; it separates vaccine immunity from recovered infection and flags people at risk of reactivation.
  • IgM core antibody — positive in infection within the past 6 months; it distinguishes acute from chronic hepatitis B when HBsAg is first found positive.
  • HBeAg and anti-HBe — e antigen signals high viral replication and infectivity; conversion to anti-HBe usually marks a quieter phase.
  • HBV DNA (viral load) — the measure of how much virus is circulating; drives treatment decisions (thresholds of 2,000 and 20,000 IU/mL) and third-trimester treatment in pregnancy (above 200,000 IU/mL).
  • ALT and AST — show whether the immune system is currently injuring the liver; the upper limit of normal for treatment decisions is about 35 U/L in men and 25 U/L in women.
  • Platelets, albumin, bilirubin and INR — fall, fall, rise and rise as cirrhosis develops; a platelet count under 150,000/µL is an early clue.
  • Hepatitis D antibody, hepatitis C antibody and HIV test — coinfections that speed liver damage and change management; hepatitis A antibody to decide on vaccination.

What usually happens next

  1. A first positive HBsAg is repeated with IgM core antibody, HBeAg/anti-HBe, HBV DNA, ALT, AST, a full blood count and liver function tests; the IgM result tells you whether this is acute or chronic, and a repeat HBsAg at 6 months confirms chronicity.
  2. If chronic, expect a fibrosis assessment (FIB-4, elastography or ultrasound), hepatitis D, hepatitis C and HIV tests, and a decision about antiviral treatment based on HBV DNA, ALT, fibrosis, age and family history. If treatment is not started, monitoring of ALT and HBV DNA every 6 to 12 months is lifelong because phases change.
  3. Liver cancer surveillance with ultrasound (often with AFP) every 6 months is recommended for people with cirrhosis, Asian men over 40 and Asian women over 50, people of African descent over 40 (some guidelines say any age), anyone with a first-degree relative with liver cancer, and people with hepatitis D.
  4. Household members and sexual partners should have the panel and be vaccinated if not immune; until a partner is known to be immune, condoms prevent transmission. Do not share razors, toothbrushes, nail clippers or needles, and cover cuts.
  5. If you are pregnant, your prenatal team needs the result: HBV DNA above 200,000 IU/mL is treated with tenofovir from 28 weeks, and your baby receives hepatitis B immune globulin and the first vaccine dose within 12 hours of birth, then completes the series and is tested at 9 to 12 months. Breastfeeding is safe once the baby has been immunized.
  6. Carry the result into every future medical encounter: before chemotherapy, rituximab, biologics, high-dose steroids or hepatitis C treatment, preventive antiviral therapy is needed. Get vaccinated against hepatitis A, limit alcohol, and check supplements and new medicines for liver toxicity.

Diet, lifestyle and natural levers with evidence

What can move HBsAg once the cause is known. Nothing here replaces finding the cause.

Know the timing traps: recent vaccination and recent exposure

Strong evidence

No diet, herb or supplement removes hepatitis B surface antigen from the blood; the only things that reliably change the result are the course of the infection and antiviral treatment. What does distort it is timing. Vaccine-derived antigen can give a reactive HBsAg for up to 2 to 3 weeks after a dose (longer in newborns and people on dialysis), so a panel drawn in that window is repeated. After an exposure, HBsAg takes 1 to 9 weeks to appear, so a negative test in the first month is provisional and the panel is repeated at 1 to 2 and 6 months. Resolution of chronic infection happens on its own in only about 1 percent of carriers a year.

Alcohol: avoid it, or keep it very low

Strong evidence

Alcohol and hepatitis B act together on the liver. In large Asian cohorts, heavy drinking (more than about 40 to 60 g a day, 3 to 4 standard drinks) in people with chronic hepatitis B roughly doubled the risk of cirrhosis and liver cancer, and some studies find risk rising at lower intakes. Alcohol also increases HBV replication in laboratory models. Guidelines advise people with chronic hepatitis B to abstain or, at most, to keep intake well under general population limits, and anyone with fibrosis or raised ALT to avoid alcohol entirely.

Coffee

Moderate evidence

A meta-analysis of 18 cohort studies found each additional 2 cups of coffee a day was associated with about 35 percent lower risk of liver cancer, with the association holding in people with hepatitis B, and separate cohorts of hepatitis B carriers link regular coffee drinking to lower ALT and slower fibrosis. These are observational findings, so they prove association rather than cause, but they are consistent across populations and both caffeinated and decaffeinated coffee show benefit.

Coffee does not replace monitoring or antiviral treatment. Limit it if it worsens reflux, anxiety or sleep.

Weight, fatty liver and metabolic health

Moderate evidence

Fatty liver coexists with chronic hepatitis B in about a quarter to a third of people in Western countries and independently increases the risk of fibrosis progression and liver cancer, and diabetes roughly doubles liver-cancer risk in hepatitis B carriers. Losing 7 to 10 percent of body weight through diet and activity reduces liver fat and inflammation in trials of people with fatty liver, and controlling blood sugar, blood pressure and lipids reduces the metabolic contribution to liver injury. Regular physical activity is associated with lower liver-cancer incidence in large cohorts.

Avoid liver-toxic supplements and aflatoxin-contaminated foods

Moderate evidence

Herbal and dietary supplements cause about a fifth of drug-induced liver injury in US registries, and an already infected liver has less reserve. Kava, high-dose green tea extract, comfrey, chaparral, germander, some traditional remedies containing undeclared ingredients, bodybuilding and weight-loss blends, and vitamin A above 10,000 IU a day are documented offenders. Aflatoxin, a mold toxin in poorly stored grains, peanuts and corn, multiplies liver-cancer risk in hepatitis B carriers many-fold in studies from China and Africa; it is tightly regulated in the US food supply but relevant for imported or home-stored produce. Tell your clinician about everything you take.

Herbal products marketed to 'clear' or 'treat' hepatitis B have no trial evidence of removing HBsAg or HBV DNA, and several have caused liver injury.

When to see a clinician promptly

  • Confusion, unusual drowsiness, easy bleeding, or vomiting blood or passing black stools in anyone with hepatitis B: possible acute liver failure or bleeding varices, call emergency services.
  • Yellowing of the skin or eyes, dark urine, pale stools, or severe nausea with a new positive HBsAg: acute hepatitis needs assessment within a day, with INR and bilirubin checked.
  • A positive HBsAg that has never been fully evaluated (HBV DNA, e antigen, ALT, fibrosis assessment) or that has not been monitored in more than a year.
  • A positive HBsAg or core antibody and a plan to start chemotherapy, rituximab, biologic drugs, high-dose steroids or hepatitis C treatment: preventive antiviral treatment must be arranged first.
  • A positive HBsAg in pregnancy, so that HBV DNA can be checked and the newborn's immune globulin and vaccine arranged within 12 hours of birth.
  • A needlestick, sexual exposure to a known positive person, or a newborn of an HBsAg-positive mother: immune globulin and vaccination are most effective within 24 hours (12 hours for newborns).
  • New pain or fullness under the right ribs, unexplained weight loss, or a rising AFP in someone with chronic hepatitis B, to check for liver cancer.

Frequently asked questions

What does hepatitis B surface antigen reactive mean?

Reactive (positive) means the surface protein of the hepatitis B virus is in your blood, which means the virus is present and you have a current infection. Whether it is new or long-standing is shown by the IgM core antibody (positive in the first 6 months) and by repeating the HBsAg after 6 months; if it is still positive then, the infection is chronic. A reactive result also means you can pass the virus on, so partners and household members should be tested and vaccinated.

Can HBsAg be positive after a hepatitis B vaccine?

Yes, briefly. The vaccine is made of purified surface antigen, and enough of it can circulate to make the HBsAg test reactive for up to about 2 to 3 weeks after a dose, longer in newborns and dialysis patients. The core antibody stays negative, because the vaccine contains no core protein, and a repeat test a few weeks later is non-reactive. Blood drawn for a hepatitis B panel should ideally be taken before a vaccine dose or at least 3 to 4 weeks after one.

How do I read my hepatitis B panel results?

Look at the three results together. HBsAg positive means current infection. HBsAg negative, surface antibody positive and core antibody negative means you are immune from vaccination. HBsAg negative with both antibodies positive means you had hepatitis B in the past, recovered and are immune. All three negative means never infected and not immune; vaccination is recommended. Core antibody positive alone is usually a distant resolved infection, occasionally a false positive or low-level infection, and is clarified with HBV DNA or a vaccine dose followed by a repeat surface antibody.

What does hepatitis B core antibody positive mean?

The core antibody is made only in response to actual infection with the hepatitis B virus, never to the vaccine, and it lasts for life. On its own it tells you the virus has been in your body at some point. If HBsAg is also positive, you have a current infection; if HBsAg is negative and surface antibody is positive, you recovered and are immune. A positive core antibody matters later in life because dormant virus can reactivate during chemotherapy or immunosuppressive treatment, so it should be mentioned to any clinician planning such therapy.

Can HBsAg become negative?

Yes. In acute infection it disappears within 6 months in about 95 percent of adults as they recover. In chronic infection, spontaneous loss of HBsAg occurs in roughly 1 percent of people a year, and is more likely in those with low HBV DNA and falling quantitative HBsAg levels; current antiviral tablets suppress the virus very effectively but lead to HBsAg loss in only a few percent of people over years. HBsAg loss, especially with appearance of surface antibody, is called a functional resolution and greatly lowers the risk of complications, although liver-cancer surveillance continues if cirrhosis was already present.

Is a positive HBsAg contagious?

Yes. Anyone who is HBsAg positive can transmit hepatitis B through blood, semen and vaginal fluids and from mother to baby at birth, with the highest infectivity when HBeAg is positive and HBV DNA is high. It spreads through sex, shared needles, razors or toothbrushes, needlesticks, and contact with open sores; it is not spread by food, water, hugging, kissing, coughing, sharing dishes or breastfeeding. The vaccine protects contacts almost completely, which is why testing and vaccinating partners and household members is the first step after a positive result.

What does HBsAg positive in pregnancy mean for my baby?

Without intervention, 70 to 90 percent of babies born to mothers with high viral loads become infected, and nearly all of those develop chronic hepatitis B. With the standard measures, hepatitis B immune globulin and the first vaccine dose within 12 hours of birth followed by the full vaccine series, transmission falls to under 5 percent, and adding tenofovir for the mother from 28 weeks when HBV DNA is above 200,000 IU/mL lowers it further, to around 1 percent or less. Cesarean delivery is not needed for hepatitis B alone, breastfeeding is safe once the baby has been immunized, and the baby is tested for HBsAg and surface antibody at 9 to 12 months.

What is the difference between HBsAg and hepatitis B surface antibody?

They are opposites in meaning. HBsAg (the antigen) is a piece of the virus itself; its presence means current infection. Hepatitis B surface antibody (anti-HBs or HBsAb) is your immune system's response to that antigen; its presence at 10 mIU/mL or more means you are protected, either from vaccination or from recovering from a past infection. In nearly everyone only one of the two is positive at a time: the antigen during infection, the antibody after recovery or vaccination. The rare person with both has a chronic infection and is managed as infected.

References

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This page is educational and is not medical advice or a diagnosis. Lab results have to be interpreted together with your history, symptoms and other results by a clinician who knows you. Do not start or stop a supplement to change a lab value before the cause is known.