Serum Immunoglobulin G (IgG) Level

What Does IgG Measure?

IgG is the most abundant antibody in your blood, playing a key role in defending against bacteria and viruses. It can also help your body recognize and remember past infections, which is why it’s important for long-term immunity. Levels can vary depending on your health, immune response, and exposure to infections.

Why Might You Need This Test?

Doctors may order an IgG test to check for immune system function, diagnose conditions like immunodeficiency, evaluate responses to vaccines, or monitor chronic diseases such as lupus or rheumatoid arthritis. It can also help assess how well your body is producing antibodies after an infection.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The blood is then processed to separate the serum (the liquid part without clots) for testing. This test is typically done on serum, but plasma can also be used depending on the lab’s method.

Common Reasons for Testing

IgG testing is often used to diagnose or monitor conditions like HIV, tuberculosis, autoimmune diseases, or to check for proper immune response after vaccination. It can also help identify if someone has a weakened immune system due to genetic disorders, cancer treatments, or other health conditions.