Immunoassay for Immunoglobulin G (IgG) in serum/plasma

What Does IgG Serve in the Body?

IgG is the most abundant antibody in your blood and plays a critical role in defending against bacteria and viruses. It helps neutralize toxins, opsonize pathogens for removal, and provide long-term immunity after an infection has passed. Low IgG levels may indicate immune deficiencies, while high levels could be due to chronic infections, autoimmune conditions, or certain medications.

When Might You Need This Test?

Your doctor may order an IgG test if you have symptoms of a weakened immune system, such as frequent infections, slow wound healing, or unexplained fatigue. It’s also used to monitor immune responses in conditions like HIV, lupus, or after organ transplants. Children with recurrent infections may also be tested for IgG levels.

Common Reasons for Testing

IgG testing is often part of an evaluation for immune-related disorders, including congenital or acquired immunodeficiency. It may also be checked during pregnancy to assess maternal-fetal immunity or after vaccination to confirm 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 a blood sample. If you’re on blood thinners, let your doctor know before the test.