Does this test have other names?

IgM anti-HBc, HBcAb

What is this test?

This test looks for antibodies called IgM in your blood. The test is used to find out whether you are actively infected with the hepatitis B virus (HBV).

HBV has a central core and a surrounding envelope. Your immune system makes IgM antibodies for the core of HBV during the active stage of infection. Hepatitis B core IgM antibodies begin to appear in your blood several weeks after you are first infected with HBV. People who have had the hepatitis B vaccine will not have the core antibody in their blood.

HBV is one of five hepatitis viruses. The others are hepatitis A, C, D, and E. Most hepatitis infections are caused by these five viruses. HBV is spread through blood, seminal fluid, and vaginal secretions. It can take 60 to 150 days to develop symptoms of hepatitis B after you become infected. The virus causes an infection in the liver. In most cases, this virus clears up on its own within 6 months. But in a small portion of adults and a larger portion of children, the virus does not go away. This is especially true for newborns. This is called having a chronic infection. It may lead to liver cell damage, scarring, cirrhosis, or liver cancer.

Why do you need this test?

You may need this test if your health care provider suspects you have a liver infection caused by HBV. You may also need this test if you have symptoms of hepatitis B. Symptoms usually start slowly. Many people have no symptoms or only feel like they have a mild case of the flu. You may not have symptoms until the infection is chronic or severe.

The most common symptom is extreme tiredness. Other symptoms may include:

• Nausea.

• Loss of appetite.

• Muscle aches.

• Fever.

• Jaundice, or yellowed skin and eyes.

• Dark-colored urine.

• Belly pain.

• Swelling and confusion. This is in extreme cases.

You may also have this test if you have a history that puts you at risk for being in contact with the virus. Risk factors for hepatitis B infection include:

• Having sex with someone infected with the virus.

• Living in close contact with someone who has the virus.

• Being a man who has sex with men.

• Being a child born to a mother who has the virus.

• Sharing needles for intravenous (IV) drug use.

• Working in a health care center where you are exposed to blood.

• Getting a blood transfusion or organ transplant. This is less common with active screening.

What other tests might you have along with this test?

Your health care provider may order other blood tests to look for HBV. These tests can look for antigens on the surface, envelope, and core of the virus, as well as the antibodies to these antigens. Because the symptoms of all five hepatitis infections are much the same, this blood test is often done along with other hepatitis blood tests to tell your provider which type of virus you may have.

What do your test results mean?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your health care provider what your test results mean for you.

Normal results are negative or nonreactive, meaning that no hepatitis B core IgM antibodies were found.

If your test is positive or reactive, it may mean you are actively infected with HBV. In most cases, this means that you will recover within 6 months. If you recover, you will have immunity from the virus and will not be able to pass the virus to others. If you don't recover in 6 months, the virus may stay in your blood, cause liver problems, and can infect others. Your provider may give you medicines if you don't recover after 6 months.

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore. 

What might affect your test results?

Other factors aren't likely to affect your results.

How do you get ready for this test?

You don't need to prepare for this test. Be sure your health care provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.