Serum or plasma concentration of total immunoglobulin G (IgG) by immunoassay

What Is Immunoglobulin G (IgG)?

IgG is the primary antibody in your bloodstream. It’s produced by your immune system in response to infections and helps neutralize toxins and viruses. IgG is also important for transferring immunity from mother to baby during pregnancy.

Why Might You Need This Test?

Your doctor may order this test if you have symptoms of low immunity, such as frequent infections, slow wound healing, or if you’re being treated for conditions like HIV, autoimmune diseases, or certain cancers. It can also help monitor immune responses after vaccination or during treatments like chemotherapy.

When Is This Test Performed?

This test is typically done by drawing blood from a vein in your arm. The blood sample is then sent to a lab for analysis using an immunoassay method, which detects and measures the IgG antibodies in your serum or plasma.

What to Expect Before the Test

There are usually no special preparations needed for this test. You may be asked to fast for 8–12 hours before the blood draw if your doctor specifies it, but this is not always required. Avoid strenuous activity or medications that might affect your immune response 24 hours before the test.