Serum Immunoglobulin G (IgG) Level

What Does This Test Measure?

IgG is the most abundant antibody in your blood and is crucial for defending against bacteria and viruses. It circulates in your serum (the liquid part of blood after clotting) and helps your immune system remember past infections for faster protection if you encounter the same pathogen again.

Why Might You Need This Test?

Your doctor may order an IgG test to check for low or high levels, which can indicate conditions like immune deficiencies, chronic infections, or certain autoimmune diseases. It’s also used in monitoring treatments for conditions affecting the immune system.

When Is This Test Performed?

A blood sample is typically taken from a vein in your arm. The test is usually done during a routine blood draw, often when you’re at a doctor’s office, clinic, or lab. Results may be reviewed shortly after or within a few days, depending on lab processing times.

What Are Common Reasons for Testing?

Common reasons include diagnosing or monitoring immune-related conditions (e.g., HIV, lupus), assessing immune function in newborns, or evaluating responses to vaccines or treatments for immune disorders.