Serum/plasma concentration of total immunoglobulin G (IgG) by nephelometry

What Is Immunoglobulin G (IgG)?

IgG is the primary antibody in your blood that plays a crucial role in defending against bacteria and viruses. It’s produced by your immune system in response to infections and helps remember past illnesses to provide quicker protection if you encounter the same pathogen again. IgG is also found in other body fluids like breast milk, providing passive immunity to newborns.

Why Might You Need This Test?

Your healthcare provider may order this test if you have symptoms of a weakened immune system, such as frequent infections, slow wound healing, or unexplained fatigue. It can also be used to monitor conditions like HIV, lupus, or other autoimmune diseases where IgG levels may be abnormal.

When Is This Test Performed?

This test is typically done as part of a routine blood draw. It may be scheduled before starting certain treatments (e.g., chemotherapy, immune-modulating drugs) to check how your immune system is functioning or to monitor treatment progress.

What Does a Low or High IgG Level Mean?

Low IgG levels may indicate an immune deficiency, where your body struggles to fight infections effectively. High IgG levels can sometimes suggest chronic infections, autoimmune diseases, or other health conditions that trigger excessive antibody production.