Serum Immunoglobulin G (IgG) Level

What Is Immunoglobulin G (IgG)?

IgG, or Immunoglobulin G, is the most abundant antibody in your blood. It plays a key role in fighting off infections by helping your immune system recognize and remember pathogens like bacteria and viruses. IgG is produced by your plasma cells, a type of white blood cell, and circulates throughout your body to provide long-term immunity.

Why Might You Need This Test?

Doctors may order an IgG test to check for immune system issues, such as low IgG levels that could indicate a weakened immune response. It’s also used to monitor conditions like HIV, certain autoimmune diseases, or after treatments like chemotherapy that might affect antibody production.

When Is an IgG Test Performed?

This test is often done when you have symptoms like frequent infections, unexplained fatigue, or if you’re being treated for a condition that could influence antibody levels. It may also be part of routine blood work for certain medical evaluations.

How Is the Test Done?

A small blood sample is taken from a vein in your arm. The blood is then sent to a lab to measure the IgG concentration using an immunoassay method, which detects the presence and amount of IgG antibodies.