Total Serum Immunoglobulin G (IgG) Level

What Does IgG Measure?

IgG is the most abundant antibody in your blood and plays a key role in defending against bacteria and viruses. It’s also involved in immune responses to toxins and foreign substances. Your body produces IgG throughout your life to provide broad protection.

Why Might You Need This Test?

Doctors may order an IgG test to check for immune system function, diagnose conditions like immunodeficiency, monitor treatment for diseases like lupus or HIV, or evaluate responses to vaccines. It can also help identify issues with antibody production in newborns or individuals with chronic illnesses.

Sample Collection and Preparation

This test uses a blood sample drawn from a vein, typically in your arm. The blood is collected in a special tube that separates serum (the liquid part without clots) for testing. No special preparation is needed, but fasting is usually not required.

Test Results and Interpretation

Results are reported as a concentration of IgG in the serum. While reference ranges vary by lab, lower than expected levels may suggest immune deficiencies, while higher levels might indicate chronic infections, autoimmune diseases, or certain cancers. Your doctor will interpret results in the context of your health history.