Immunoglobulin G (IgG) in Serum

What Is Immunoglobulin G (IgG)?

IgG is the most common type of antibody in your blood. Antibodies are proteins that help your immune system recognize and fight off bacteria, viruses, and other invaders. IgG is particularly important because it can cross the placenta to provide passive immunity to your baby during pregnancy and early life. It also remains in your body for a long time after an infection has passed, providing ongoing protection.

Why Might You Need This Test?

Your doctor may order an IgG test to check for low or high levels, which can indicate conditions like immune deficiencies, infections, or certain autoimmune diseases. It may also be used to monitor treatment responses in people with chronic illnesses or to assess immune function in newborns or infants.

When Is This Test Done?

This test is typically performed by drawing blood from a vein in your arm. The blood sample is then sent to a lab for analysis. Results are usually available within a few days, depending on the lab’s processing time.

What Does the Test Tell You?

IgG levels can provide clues about your immune system’s strength. Low IgG levels might suggest a weakened immune response, while very high levels could indicate chronic infections, certain cancers, or other health conditions. Your doctor will interpret the results in the context of your overall health and medical history.