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

What Is Immunoglobulin G (IgG)?

IgG is the most common type of antibody in your blood. It plays a key role in fighting off infections and helping your body remember past illnesses, which helps prevent future infections. Antibodies like IgG are produced by your immune system to recognize and neutralize harmful substances, such as bacteria and viruses.

Why Might You Need This Test?

Your doctor may order an IgG test to evaluate your immune system function. This could be done if you have symptoms of a weakened immune system, such as frequent infections, unusual bruising, or unexplained fatigue. It may also be used to monitor immune responses after vaccination or to diagnose conditions like immunodeficiency disorders.

Common Reasons for Testing

Common reasons for this test include assessing immune function in people with recurrent infections, evaluating immune responses to vaccines, diagnosing conditions like HIV, checking for immune deficiencies, or monitoring diseases that affect the immune system.

What to Expect Before the Test

No special preparation is usually needed for this test. You may be asked to fast for a few hours before the blood draw if your lab requires it, but this is not always the case. Bring any medications or supplements you take regularly to your appointment.