Hepatitis B Blood Test Results Explained: HBsAg, Anti-HBs & Anti-HBc

Hepatitis B is easily passed on through sex without a condom, and many people who have it don't know. A blood test is the only way to find out, but a result usually lists several markers, most often HBsAg, anti-HBs and anti-HBc, and each one means something different. This guide explains what each marker shows and how to read hepatitis B blood test results together. Ovio's hepatitis B test is done at home in Bangkok.

What Is Hepatitis B?

Hepatitis B is an infection of the liver caused by the hepatitis B virus (HBV). In adults, most new infections clear by themselves within six months. Some become chronic, lasting for life, and chronic hepatitis B can slowly damage the liver for decades before causing cirrhosis, liver failure or liver cancer. Found early, it can be monitored and, when needed, treated with antiviral tablets that greatly reduce those risks.

How hepatitis B spreads

Hepatitis B passes through blood, semen and vaginal fluid:

• Sex without a condom with someone who has hepatitis B. The risk is higher with more partners, and in people who aren't vaccinated.
• Sharing needles or syringes, and sharing razors, toothbrushes or nail clippers that may carry traces of blood.
• Unsterile equipment for tattoos, piercings or medical and beauty procedures.
• From mother to baby at birth. This is why pregnant women are tested and babies are vaccinated at birth.

It isn't spread by kissing, hugging, sharing food or cutlery, or coughing.

What Are the Symptoms of Hepatitis B?

1. A new (acute) infection

Many adults have no symptoms at all. When symptoms do appear, usually one to four months after exposure, they can feel like flu at first: fever, tiredness, loss of appetite, nausea and vomiting. Some people have discomfort under the right ribs, where the liver is, then dark urine, pale stools and yellowing of the skin and eyes (jaundice). Most adults recover and clear the virus within six months, and are then immune for life. Babies and young children who catch it are much more likely to develop chronic infection.

2. A long-term (chronic) infection

Chronic hepatitis B means the body hasn't cleared the virus after six months. It usually causes no symptoms for years, while the virus can still inflame and scar the liver. That's why a blood test, not how you feel, is the way to find it.

The Three Hepatitis B Blood Test Markers

• HBsAg (hepatitis B surface antigen): a protein from the surface of the virus. If it's positive, the virus is in your blood now. It usually becomes detectable 1 to 12 weeks after infection. Positive for more than six months means chronic hepatitis B.
• Anti-HBs or HBsAb (hepatitis B surface antibody): the antibody that protects you. It's made after vaccination, or after you've had hepatitis B and cleared it.
• Anti-HBc or HBcAb (hepatitis B core antibody): an antibody to the core of the virus. It shows you've been infected at some time, past or present. Vaccination doesn't make it, so it tells infection and vaccination apart. An IgM version shows a recent infection.

Hepatitis B Blood Test Results Explained

Doctors read the three markers together. These are the most common patterns:

If HBsAg is positive, further tests tell a new infection from a chronic one: an IgM anti-HBc test is positive in a recent infection, and HBsAg that is still positive six months later means chronic infection. Liver function tests and an HBV DNA test show how active the virus is and whether treatment is needed. Many people with chronic hepatitis B need regular monitoring rather than immediate treatment. Sexual partners and people you live with should be tested and vaccinated if they aren't already protected.

Hepatitis B Testing in Bangkok

Whether you've had sex that may have put you at risk, aren't sure you completed the vaccine course, or simply want to know your status, a hepatitis B test is one of the most useful blood tests to have at least once as an adult. Hepatitis B testing is available at hospitals and clinics across Bangkok.

If you'd rather not go to a clinic, Ovio's at-home STI testing brings a doctor to your home, condo, hotel or office at a date and time you choose, for Thai and international clients. The HBsAg test for current infection is ฿990, and it's included in the Ovio Essential package (฿5,990) with HIV, syphilis, hepatitis C and an 18-infection PCR panel. Not sure which tests you need? See which STI tests should I get?

Frequently Asked Questions

Are hepatitis B blood tests accurate?

Yes, laboratory hepatitis B tests are very accurate. The main limit is timing: HBsAg can take up to 12 weeks after infection to become positive, so a test soon after an exposure may need repeating.

What should my anti-HBs level be?

10 mIU/mL or higher is considered protective, whether it comes from vaccination or a cleared infection. Levels often fall below 10 in the years after vaccination, but most people who responded to the vaccine stay protected. If you're at ongoing risk, your doctor may suggest a booster and a repeat test.

How long does the hepatitis B vaccine last?

After a full course, protection lasts at least 20 years and probably for life, according to the World Health Organization. Most people don't need a booster.

Does a positive anti-HBc mean I have hepatitis B now?

Not necessarily. It means you've been infected at some point. If HBsAg is negative and anti-HBs positive, the infection is over and you're immune. If HBsAg is positive, the infection is current.

Is hepatitis B curable?

Most adults clear a new infection by themselves. Chronic hepatitis B isn't usually cured, but daily antiviral tablets control the virus very well and greatly lower the risk of cirrhosis and liver cancer.