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 germs like bacteria and viruses. IgG is particularly important for providing long-term immunity after you recover from an infection or receive a vaccine. It also plays a role in protecting against certain diseases during pregnancy and in newborns.

Why Might You Need This Test?

Your healthcare provider may order an IgG test if you have symptoms of a weakened immune system, such as frequent infections, slow healing of wounds, or unexplained fatigue. It may also be used to monitor conditions like HIV, lupus, or other autoimmune diseases, or to check for immune deficiencies or responses to vaccines.

Common Uses and Conditions

IgG tests are commonly used to diagnose or monitor conditions affecting the immune system, such as immune deficiencies, infections, or autoimmune diseases. They may also be part of a broader evaluation for chronic illnesses or to assess vaccine effectiveness.

What Does a Low or High IgG Level Mean?

Low IgG levels may indicate an immune system that isn’t working properly, which can make you more susceptible to infections. High IgG levels might suggest an overactive immune response, chronic infections, or certain autoimmune conditions. However, results alone don’t diagnose a condition—they’re part of a larger picture.