Immunoglobulin G (IgG) Subclass 1, Substance Concentration in Serum

What Does IgG1 Measure?

IgG1 is one of the four subclasses of Immunoglobulin G (IgG), the most common antibody in your blood. It plays a key role in defending against bacterial and viral infections. Your body produces IgG1 to help neutralize toxins and pathogens, and it remains in your system for long-term protection. Levels can vary based on immune response, health status, or certain medical treatments.

Why Might You Need This Test?

Doctors may order an IgG1 test if you have symptoms of a weakened immune system, such as frequent infections, autoimmune diseases, or if you’re being evaluated for conditions like HIV, certain cancers, or immune deficiencies. It can also help monitor treatment responses in patients with chronic illnesses.

What Could Abnormal Results Mean?

Elevated IgG1 levels might suggest an overactive immune response, such as in autoimmune diseases or chronic infections. Lower-than-normal levels could indicate an immune deficiency or conditions affecting antibody production, such as certain cancers or HIV.

How Is This Test Performed?

A blood sample is taken from a vein, usually in your arm. The blood is then processed to measure the concentration of IgG1 antibodies in your serum. The test is typically done in a lab using immunoassay methods to detect and quantify the antibody.