The IgG test for HSV-2 is a serological test that checks for the presence of immunoglobulin G (IgG) antibodies specific to the HSV-2 virus in your bloodstream. IgG antibodies are produced by the immune system in response to an infection. This test is often used to diagnose a current or past HSV-2 infection because the antibodies can persist in the blood for a long time, even after the initial infection has resolved.