Serum Immunoglobulin G (IgG) Concentration

What Is Immunoglobulin G (IgG)?

IgG is a type of protein called an antibody, which plays a key role in your immune system. It’s produced by your immune cells in response to infections, vaccines, or other triggers. IgG is the most abundant antibody in your blood and helps protect you from diseases by marking invaders (like bacteria or viruses) for destruction by other immune cells.

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, chronic infections, or certain autoimmune diseases. It may also be used to monitor responses to treatments, such as vaccines or medications that affect immunity.

When Is an IgG Test Done?

This test is typically performed on a blood sample drawn from a vein. You may have a small needle inserted to collect blood, and you’ll usually feel a brief pinch. The sample is then sent to a lab for analysis.

What Does an IgG Test Tell You?

Results can help identify whether your immune system is functioning normally or if there’s an issue, such as a weakened immune response, overactive immune system, or exposure to certain infections. However, IgG alone doesn’t diagnose a specific condition—it’s often part of a broader evaluation.