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Hepatitis B Test: Which Blood Tests and What They Mean

By Richard D. Porter, Patient Advocate Updated

Quick answer

The CDC recommends a three-part blood test for hepatitis B, called the triple panel: HBsAg, anti-HBs and total anti-HBc. Together they show whether someone has a current infection, had one in the past, or is protected by vaccination. The CDC says all adults 18 and older should be tested at least once, and pregnant women in every pregnancy. A single HBsAg test shows whether an infection is present now, but it does not show immunity.

The test you need

Test
Hepatitis B triple panel: HBsAg, anti-HBs and total anti-HBc
Sample
Blood
When
The CDC gives no set post-exposure window for hepatitis B. It says the average incubation period is 60 days (range 40 to 90 days). Ask a clinician when to test after a possible exposure.
Results
STDCheck says its hepatitis B results are ready in 1 to 2 days. A lab or clinic may differ.

Hepatitis B is a virus that affects the liver. The CDC says people with hepatitis B often don’t have symptoms, so a blood test is how most people find out.

What is the hepatitis B triple panel?

The CDC recommends screening with a triple panel, which is three blood tests run together:

  • HBsAg (surface antigen). The CDC says its presence indicates that a person is infectious. Negative means no current infection was found. After a hepatitis B vaccine dose it can be briefly positive, for up to 30 days.
  • Anti-HBs (surface antibody). The CDC says it is generally read as recovery and immunity.
  • Total anti-HBc (core antibody). The CDC says it indicates previous or ongoing infection, with no way to tell when. People who are immune only from the vaccine do not develop it.

Read together, these show whether someone has a current infection, a past one that has cleared, vaccine protection, or no protection at all.

What do the results mean?

A clinician should go through your results, but these patterns give a sense of what they can show:

  • HBsAg negative, anti-HBs positive. Often immunity from a past infection or from vaccination.
  • HBsAg positive. A current infection that needs follow-up with a clinician.
  • All three negative. CDC’s interpretation is susceptible (never infected), and it recommends offering the vaccine.

The CDC says an isolated core antibody result (anti-HBc only) has several possible explanations, and lists an action for each.

Who should get tested for hepatitis B?

The CDC recommends that all adults 18 and older be tested at least once, and that pregnant women be tested in every pregnancy, preferably in the first trimester. People with ongoing risk need periodic testing.

How soon after exposure can a hepatitis B test find it?

The CDC doesn’t give a single post-exposure window. It does say the average incubation period is 60 days, with a range of 40 to 90 days. If you have had a recent possible exposure, ask a clinician when to test, and whether to repeat a negative result.

If the exposure is known and recent, such as sex with someone who has hepatitis B, time matters more than testing. The CDC’s guidelines say preventive treatment should start as soon as possible after a discrete, identifiable exposure to an HBsAg-positive source, preferably within 24 hours. A clinician decides what you need, so call one or go to urgent care promptly.

Where can I get a hepatitis B test?

A doctor, sexual health clinic or local health department can order the panel. The CDC’s GetTested site lists confidential, free or low-cost testing. Because not every STD panel includes hepatitis B, ask for it by name.

STDCheck lists hepatitis B as an individual test and in its 10-test panel, with a blood sample taken at a testing center. Its page describes a test for the surface antigen, with a second confirmation test if the first is positive, at no extra cost. That means it checks for a current infection, but it doesn’t show whether you are immune. If you want to know your vaccine status, ask a clinic for the full panel.

What if I’m pregnant?

The CDC recommends testing for HBsAg in every pregnancy, preferably in the first trimester. Its STI guidelines also say pregnant women who are HBsAg-positive should be reported and referred to a specialist, and that testing is repeated at delivery for those at high risk. If you are pregnant and unsure of your status, ask your prenatal clinician about the test early.

Should I get vaccinated?

The CDC’s STI guidelines say hepatitis B vaccine should be routinely offered to all unvaccinated people attending STD clinics, starting at the first visit. The anti-HBs part of the panel is the one the CDC links to immunity. Ask your clinician what makes sense for you.

Get care now if

  • You think you were exposed to hepatitis B in the last few days, for example by a partner known to have it, and you are not vaccinated. Contact a clinician or urgent care now, because preventive treatment is time-sensitive.
  • Your skin or the whites of your eyes look yellow
  • Dark urine, pale stools, or a fever with belly pain
  • You are pregnant and your test is positive or you are not sure of your status, so tell your prenatal clinician

Call 911 for a medical emergency. Otherwise, an urgent care clinic, sexual health clinic or your doctor can see you.

When to test

  1. Once, as an adult, with no exposure neededThe CDC recommends screening all adults 18 and older for hepatitis B at least once in their lifetime, using the triple panel.
  2. In every pregnancyThe CDC recommends testing for HBsAg in each pregnancy, preferably in the first trimester.
  3. A known recent exposure, such as a partner who has hepatitis BDon't wait for a test. Contact a clinician or urgent care promptly, because the CDC says preventive treatment should start as soon as possible after a known exposure.
  4. After a possible exposure, if you want a resultAsk a clinician when to test. The CDC gives no single window.

Common questions

What is the hepatitis B triple panel?

It is three blood tests run together. HBsAg is a protein from the virus, anti-HBs is the protective antibody, and total anti-HBc shows past or current infection. The CDC now recommends this panel for screening, rather than a single test.

What does a positive anti-HBs result mean?

The CDC says anti-HBs is generally read as recovery and immunity. The CDC also says people who are immune from the vaccine do not develop anti-HBc. A clinician reads it together with the other two results.

Is hepatitis B included in a full STD panel?

It depends on the panel, so check the list. STDCheck's 10-test panel lists hepatitis B, and its page describes a test for the surface antigen. That checks for current infection, but it doesn't show whether you are immune.

Can hepatitis B be spread by sex?

Yes. The CDC says unprotected sex with an infected partner is a primary risk factor for infection among adolescents and adults. A vaccine protects against it, and the CDC says it should be offered to all unvaccinated people attending STD clinics.

Next: Hepatitis B triple panel: HBsAg, anti-HBs and total anti-HBc.

Blood. The CDC gives no set post-exposure window for hepatitis B. It says the average incubation period is 60 days (range 40 to 90 days). Ask a clinician when to test after a possible exposure.

Read next

Sources

This guide is general information written by a patient advocate using public health sources. It is not a diagnosis. Only a clinician or a lab test can tell you whether you have an infection. Read how we write and check our guides.