Immunoglobulin A (IgA)
Immune system healthImmunoglobulin A (IgA) is the main antibody that protects the lining of your gut, airways and other mucous membranes.
Also known as: total IgA, IgA, serum IgA
In coeliac testing, total IgA is measured alongside the coeliac antibody tTG-IgA, because that antibody is itself an IgA. If your body makes too little IgA, the tTG-IgA result can look normal even when coeliac disease is present. Low IgA (selective IgA deficiency) is the most common antibody deficiency and is more frequent in people with coeliac disease. It often causes no symptoms, though some people get more frequent infections of the airways or gut. If your IgA is low, an IgG-based coeliac test is used instead.
Why this matters
IgA levels reflect how well your mucosal immune system is functioning. Low IgA (selective IgA deficiency) is one of the most common immune deficiencies and can lead to recurring sinus, lung, or gut infections. It is also important because many celiac disease screening tests rely on IgA-based antibodies. If your total IgA is low, those tests can give false-negative results.
Elevated IgA may point to chronic infections, liver disease (especially alcohol-related), or autoimmune conditions. In screening, knowing your IgA level helps ensure other test results are interpreted correctly.
How this connects to other biomarkers
- Low total IgA makes Anti-Transglutaminase IgA unreliable for celiac screening, so Anti-Transglutaminase IgG becomes the necessary alternative. Elevated IgA alongside high GGT and ASAT suggests alcohol-related liver stress. A low Albumin/Globulin ratio with high IgA points toward chronic immune activation or liver disease.
How often should I test Immunoglobulin A (IgA)?
Total IgA is usually measured once, together with a coeliac antibody test, as your IgA level tends to stay stable over time. A normal result means a later tTG-IgA test can be read without measuring IgA again. If your IgA is low, coeliac antibody tests from then on use the IgG type instead.
At baseline / for screening: Once, together with your first coeliac antibody test.
When monitoring an intervention or change: Routine retesting is not needed. If your IgA is low, later coeliac antibody tests use the IgG type.
Note: If your IgA is low, a normal tTG-IgA result cannot rule out coeliac disease. Some medicines that act on the immune system can lower IgA.
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