Immunoglobulin A (IgA) in Serum or Plasma, Mass Concentration

This test measures the amount of immunoglobulin A (IgA) in your blood. IgA is an antibody, a protein made by your immune system that helps defend the moist surfaces of your body, including your mouth, throat, lungs, and intestines, from germs and infection.

IgA is one of the key proteins in your immune system. It’s found in high concentrations in mucous membranes (like those in your nose and throat) and helps prevent harmful bacteria and viruses from entering your body. This test checks the total amount of IgA in your blood, which can vary depending on your health, immune status, and other factors.

Your doctor may order this test if you have frequent or unusual infections, chronic diarrhea, or other symptoms that suggest your immune system is not working as it should. It can also help monitor ongoing conditions that affect antibody levels, such as autoimmune disorders, liver disease, or certain kidney problems.

Doctors may order an IgA test to diagnose or monitor conditions like immune deficiencies, certain infections, autoimmune diseases, or to check for problems with how your body produces antibodies. It can also be part of a broader evaluation for conditions affecting the immune system or gastrointestinal health.

Common reasons for testing include repeated sinus, lung, or digestive tract infections, unexplained weight loss, long-lasting digestive symptoms, suspected celiac disease, and follow-up care for conditions such as selective IgA deficiency or other disorders that can raise or lower antibody levels.

Common reasons include evaluating recurrent infections, assessing immune function, diagnosing conditions like IgA nephropathy (a kidney disease), or checking for deficiencies in antibody production. It may also be used in research or specialized clinical settings to monitor immune responses.

Little preparation is usually needed, and you can normally eat and drink before the test, but follow any specific instructions from your doctor. Tell your care team about all medicines, vitamins, and supplements you take, since some drugs can affect IgA levels. A small blood sample will be drawn from a vein in your arm, and the process usually takes only a few minutes.

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if it involves drawing blood. Wear comfortable clothing and plan to stay near the testing site for a short time. If you’re on blood thinners or have a history of bleeding disorders, let your healthcare provider know.