The Immunoglobulin G (IgG) blood test is used to measure IgG levels, the most common type of antibody in the body. IgG plays a key role in the immune response, helping protect the body against infections and diseases. This test is used to assess immune system status and can help diagnose chronic infections, such as hepatitis or viral infections. It is also used to monitor patients with immune-related conditions, such as lupus or lymphatic disorders. The test should be performed under medical supervision, as the results require careful interpretation to determine the appropriate treatment plan.