Immunoglobulin G (IgG) in Serum/Plasma by Mass Concentration

Immunoglobulin G (IgG) is the most abundant type of antibody in your blood. Antibodies are proteins made by your immune system that help your body recognize and fight off bacteria, viruses, and other harmful substances. IgG makes up about 75% to 80% of all antibodies in your body and plays a key role in long-term protection against infections you have had before or vaccines you have received.

IgG is a type of protein (antibody) produced by your immune system to defend against infections. It’s the most abundant antibody in your blood and plays a key role in long-term immunity. Your body produces IgG in response to pathogens like bacteria and viruses, helping to neutralize them and mark them for destruction by other immune cells.

Your doctor may order an IgG test if you have frequent or unusual infections, signs of an autoimmune disease, or symptoms that suggest your immune system is not working properly. The test may also be used to check how well your body is responding to treatment or to investigate unexplained symptoms such as chronic fatigue, recurrent respiratory infections, digestive problems, or ongoing inflammation.

Doctors may order an IgG test to evaluate immune function, diagnose conditions like immunodeficiency, or monitor treatment for diseases such as HIV, lupus, or certain autoimmune disorders. It can also help assess how well your body is responding to vaccines or infections.

An IgG test is commonly used to help diagnose or monitor conditions such as immunodeficiency disorders, multiple myeloma, chronic infections, and autoimmune diseases like lupus. It can also help evaluate the immune system in people with recurring infections, check antibody levels after vaccination, and monitor patients undergoing treatments that affect immune function.

Common reasons for testing include: diagnosing primary immunodeficiency disorders (e.g., severe combined immunodeficiency), assessing immune response to infections or vaccines, evaluating autoimmune diseases (e.g., systemic lupus erythematosus), or checking for conditions like chronic infections or malabsorption syndromes that may affect antibody production.

This test is performed with a simple blood draw. A healthcare professional will clean the skin on your arm, insert a small needle into a vein, and collect a sample of blood into a tube. The procedure usually takes only a few minutes and may cause brief discomfort or minor bruising. Your sample is then sent to a laboratory, where the IgG level is measured and compared with normal reference ranges.

A blood sample is drawn from a vein, usually in your arm. The sample is then sent to a lab where it is analyzed using a specialized technique to measure the precise amount of IgG in your blood. The test typically takes a few hours to complete.