Serum Immunoglobulin G (IgG) Level

What Does This Test Measure?

IgG is the most common type of antibody in your blood. It’s produced by your immune system in response to infections and vaccines. This test helps doctors assess your immune response, check for immune deficiencies, or monitor conditions like certain autoimmune diseases or chronic infections.

Why Might You Need This Test?

Doctors may order this test if you have symptoms of low immunity (like frequent infections), if you’ve had a recent infection or vaccination, or if you’re being treated for conditions like lupus, HIV, or certain cancers. It can also help monitor immune responses in newborns or people with immune disorders.

How Is the Test Done?

A blood sample is taken from a vein in your arm. The blood is sent to a lab where it’s processed to separate serum (the liquid part without blood cells). The lab then measures the IgG concentration using an immunoassay method, which detects the antibody’s presence.

What Are Possible Results?

Results are typically reported as a concentration value (e.g., grams per liter). While reference ranges vary by lab, lower than expected levels may suggest immune deficiency, and higher levels could indicate chronic infections, inflammation, or certain immune disorders.