Serum IgG Immunoglobulin (Mass Concentration)

What Is Immunoglobulin G (IgG)?

IgG is the primary antibody produced by your immune system. It’s found in high levels in your blood and plays a key role in defending against bacteria and viruses. Unlike other antibodies, IgG can cross the placenta to provide passive immunity to your baby during pregnancy.

Why Might You Need This Test?

Doctors may order an IgG test to check for low or high levels, which can indicate conditions like immune deficiencies, infections, autoimmune diseases, or certain cancers. It’s also used in monitoring treatment responses for conditions like HIV, hepatitis, or immune-related disorders.

Common Reasons for Testing

Common reasons include diagnosing or monitoring immune system disorders, assessing immune response to vaccines, evaluating chronic infections, or checking for conditions like common variable immunodeficiency (CVID). It may also be part of a broader workup for unexplained infections or autoimmune diseases.

Sample Collection and Preparation

This test requires a blood sample drawn from a vein in your arm. No special preparation is needed, but fasting may not be required unless instructed by your healthcare provider. The sample is sent to a lab for analysis.