Serum IgG Immunoglobulin G Concentration (Mass Concentration)

What Does This Test Measure?

IgG is the primary antibody your immune system produces in response to infections, vaccines, or other immune challenges. It circulates in your bloodstream and helps neutralize pathogens like bacteria and viruses. This test specifically quantifies the mass concentration of IgG in your serum, which can help assess your immune response and overall antibody levels.

Why Might You Need This Test?

Doctors may order an IgG test if you have symptoms of a weakened immune system, such as frequent infections, slow healing of wounds, or unexplained fatigue. It’s also used to monitor immune responses after vaccines, diagnose autoimmune diseases, or evaluate conditions like HIV, lupus, or certain cancers.

How Is the Test Performed?

A blood sample is drawn from a vein in your arm. The blood is then processed to separate serum (the liquid part without clots) for testing. The IgG level is measured using a sensitive laboratory technique, such as nephelometry or immunoassay, to detect and quantify the antibody.

What Are Possible Results?

Results are typically reported as a numerical value representing the IgG concentration in your serum. While reference ranges can vary by lab, lower than expected levels may suggest immune deficiencies, while higher levels could indicate chronic infections, autoimmune diseases, or other conditions.