IgG Immunoglobulin (Serum) – Quantitative

What Does IgG Measure?

IgG is the most abundant antibody in your blood, playing a key role in long-term immunity. It’s produced by plasma cells in response to infections, vaccines, and chronic conditions. Measuring IgG helps doctors evaluate your immune system’s ability to fight pathogens and identify conditions like immunodeficiency, autoimmune diseases, or certain infections.

Why Might You Need This Test?

Your doctor may order an IgG test if you have symptoms of a weakened immune system (e.g., frequent infections, slow wound healing), suspected immunodeficiency, or if you’re being treated for conditions like lupus, rheumatoid arthritis, or chronic infections. It may also be used in newborns to check for maternal antibody transfer or in monitoring immune responses to vaccines.

Sample Collection and Preparation

A blood sample is drawn from a vein in your arm. The blood is processed to separate serum (the liquid part without clotting factors), which is then tested for IgG levels. This test is typically done in a lab using a blood sample collected in a plain red-top tube.

Common Conditions or Situations

IgG levels can be low in primary immunodeficiency disorders (e.g., severe combined immunodeficiency), certain autoimmune diseases (e.g., systemic lupus erythematosus), or after certain treatments (e.g., chemotherapy). Elevated IgG levels may occur in chronic infections, inflammatory conditions, or as a response to vaccines.