Hepatitis B Core Antibody, IgM (Serum)

What Does This Test Measure?

The test looks for IgM antibodies (a type of immune protein) that your body produces in response to the hepatitis B core antigen. These antibodies typically appear shortly after infection begins and can persist for months or years. This test is used to diagnose acute hepatitis B or rule out chronic infection when other markers are unclear.

Why Might You Need This Test?

Your healthcare provider may order this test if you have symptoms of hepatitis B (such as fatigue, jaundice, or abdominal pain), if you’ve been exposed to hepatitis B, or if you’re evaluating for acute infection when other tests (like hepatitis B surface antigen) are inconclusive.

When Might You Get False Results?

IgM antibodies can sometimes linger after infection resolves, leading to false positives. Conversely, if you’ve been vaccinated or previously infected, you may have false negatives. Your provider will consider other test results and your medical history to interpret results accurately.

What Does a Positive Result Mean?

A positive result suggests recent hepatitis B infection, meaning you may have been exposed to the virus within the past few months. This does not necessarily mean you are contagious at the time of testing, but it indicates you should seek medical evaluation and potentially start antiviral treatment if needed.