Serum Immunoglobulin G (IgG) Level

What Does IgG Serve in Your Body?

IgG is the most abundant antibody in your blood and plays a critical role in defending against bacteria and viruses. It helps neutralize toxins, opsonize pathogens, and activate immune responses. IgG levels can vary depending on your immune status, age, and health conditions, including infections, autoimmune diseases, or immune deficiencies.

Why Might Your Doctor Order This Test?

Your doctor may order an IgG test to evaluate your immune system function. Common reasons include diagnosing or monitoring conditions like immunodeficiency, chronic infections, autoimmune diseases, or assessing immune response after vaccination. It can also help determine if you have enough antibodies to protect against certain diseases.

How Is This Test Performed?

A blood sample is taken from a vein, usually in your arm. The blood is then sent to a lab where it is processed to separate serum (the liquid part without blood cells). The IgG level is measured using an immunoassay method, which detects the presence and concentration of IgG antibodies in the serum.

What Are Possible Results and What Do They Mean?

Results are typically reported as a concentration in milligrams per deciliter (mg/dL) or grams per liter (g/L). While specific reference ranges can vary by lab, lower than expected IgG levels may suggest an immune deficiency, while higher levels might be seen in chronic infections or certain autoimmune conditions. Your doctor will interpret the results in the context of your overall health and medical history.