Serum or Plasma Immunoassay for Immunoglobulin M (IgM) Antibody Against Hepatitis B Surface Antigen

What This Test Measures

IgM antibodies are a type of immune protein your body produces in response to infection. In this test, we detect whether your blood contains IgM antibodies that specifically target the hepatitis B surface antigen—a protein on the surface of the hepatitis B virus. These antibodies often appear shortly after infection but can decline over time as your immune system resolves the infection.

Why It Matters in Diagnosis

IgM anti-HBs testing helps distinguish between past and recent hepatitis B infection. Unlike IgG antibodies, which can persist long-term, IgM antibodies are usually temporary. High levels may indicate an acute infection, while low or absent levels suggest recovery or immunity from prior exposure.

When You Might Need This Test

Your healthcare provider may order this test if you have symptoms of hepatitis B (e.g., fatigue, jaundice, abdominal pain), if you’ve been exposed to hepatitis B, or as part of routine screening for certain high-risk groups (e.g., healthcare workers, travelers to endemic regions). It may also be used to monitor treatment progress or evaluate immune response.

What to Expect Before the Test

No special preparation is needed for this blood test. You may have a small needle inserted into your arm to draw blood, similar to other routine bloodwork. If you’re on blood thinners or have a history of bleeding disorders, let your provider know beforehand.