Serum IgG Immunoglobulin Level (Mass Concentration)

What Is IgG and Why Is It Important?

IgG, or Immunoglobulin G, is the most abundant antibody in your blood. It’s produced by your immune system to protect against bacteria and viruses. IgG antibodies help your body remember past infections and provide long-term immunity. This test helps doctors assess your immune response, diagnose certain conditions, and monitor treatments.

When Might You Need This Test?

Your doctor may order this test if you have symptoms of a weakened immune system, such as frequent infections, unexplained fatigue, or if you’re receiving treatment for conditions like lupus, rheumatoid arthritis, or HIV. It can also be used to check for immune deficiencies or to monitor immune responses during certain therapies.

What Does a Low or High IgG Level Mean?

Low IgG levels may suggest an immune deficiency, chronic illness, or malabsorption issues that prevent proper antibody production. High IgG levels can sometimes indicate chronic infections, autoimmune diseases, or certain types of cancer, though this isn’t always straightforward and requires clinical correlation.

How Is This Test Performed?

A blood sample is drawn from a vein in your arm. The blood is then processed to separate the serum (the liquid part without blood cells), and the IgG level is measured using a specialized laboratory technique, often an immunoassay, to detect and quantify the antibody.