IgA (Immunoglobulin A)
An IgA test measures your mucosal antibody level to assess immune function and guide celiac testing, with convenient Quest lab ordering via Vitals Vault.
This panel bundles multiple biomarker tests in one order—your report explains how results fit together.
IgA (immunoglobulin A) is an antibody your immune system uses to protect the “entry points” of your body—especially your gut, airways, and sinuses. A blood IgA test gives a snapshot of how much IgA is circulating in your serum.
This test often comes up when you have frequent respiratory or gastrointestinal infections, when your clinician is screening for immune deficiency, or when you are doing a celiac disease workup. It can also explain why certain IgA-based antibody tests may come back negative even when symptoms strongly suggest a condition.
Your IgA result is most useful when it is interpreted alongside your symptoms, infection history, and other labs. It supports clinician-directed care and does not diagnose a condition by itself.
Do I need a IgA test?
You may want an IgA test if you keep getting sinus infections, ear infections, bronchitis, or prolonged “colds,” especially if this pattern has been going on for years or you need antibiotics frequently. Low IgA can be one reason your first-line immune defenses at mucosal surfaces are less effective.
IgA is also a practical test if you are being evaluated for celiac disease. Many common celiac screening tests (such as tissue transglutaminase IgA) rely on your ability to make IgA antibodies. If your total IgA is low, those celiac antibody tests can look falsely reassuring, and an IgG-based strategy may be more appropriate.
You might also be advised to test IgA if you have chronic diarrhea, unexplained weight loss, persistent bloating, or other symptoms that raise concern for malabsorption, or if you have a personal or family history of immune disorders.
If you are currently ill, pregnant, or taking immune-modulating medications, your result can be harder to interpret. In those cases, it helps to review timing and next steps with a clinician so you do not over- or under-react to a single number.
This is a serum immunoassay performed in a CLIA-certified laboratory; results should be interpreted in clinical context and are not a standalone diagnosis.
Lab testing
Order an IgA test and schedule your blood draw at a Quest location when you’re ready.
Schedule online, results typically within about a week
Clear reporting and optional clinician context
HSA/FSA eligible where applicable
Get this test with Vitals Vault
Vitals Vault lets you order an IgA blood test without a referral and complete your draw at a nearby Quest location. If you are trying to understand recurrent infections or you are planning celiac testing, getting total IgA first can prevent confusing or incomplete workups.
After your results post, you can use PocketMD to ask targeted questions like whether your IgA level could affect celiac antibodies, what companion tests are typically paired with IgA, and when a repeat measurement makes sense. This is especially helpful if your result is borderline or if you have symptoms that do not match the lab value.
If your situation calls for a broader view of humoral immunity, you can also consider adding a companion immunoglobulins panel (commonly IgG, IgA, and IgM together) so your next step is based on a pattern rather than a single marker.
- Order online and draw at a Quest lab location
- PocketMD helps you interpret results and plan next steps
- Clear, shareable results for your clinician
Key benefits of IgA testing
- Helps evaluate recurrent sinus, lung, and gastrointestinal infections by checking a key mucosal antibody.
- Identifies possible selective IgA deficiency, a common immune finding that can change your workup plan.
- Improves celiac testing strategy by flagging when IgA-based celiac antibodies may be falsely negative.
- Adds context to chronic GI symptoms by distinguishing immune patterns from purely dietary triggers.
- Supports safer interpretation of allergy and autoimmune antibody tests that depend on IgA responses.
- Provides a baseline you can trend over time, especially if symptoms change or treatment is started.
- Pairs well with IgG and IgM testing to map humoral immunity more completely when needed.
What is IgA?
IgA (immunoglobulin A) is a class of antibody made by B cells. It is especially important on mucosal surfaces—your nose, throat, lungs, and intestines—where it helps neutralize viruses, bacteria, and toxins before they cause deeper infection.
Most of the IgA your body produces is secreted into mucus, saliva, tears, and the gut. The lab test on this page measures total IgA in your blood (serum IgA), which is not identical to secretory IgA in the gut, but it often correlates with your overall capacity to make IgA.
IgA levels can be low because of a primary immune trait (such as selective IgA deficiency), because of certain medications or illnesses, or rarely because of broader immune problems that also affect other immunoglobulins. IgA can also be high when your immune system is chronically stimulated, such as with ongoing inflammation, infection, or some liver and autoimmune conditions.
Serum IgA vs. secretory IgA
Serum IgA is what your lab report shows from a blood draw. Secretory IgA is the form that coats mucosal surfaces and is often discussed in stool testing. A normal serum IgA does not guarantee optimal mucosal immunity, but a very low serum IgA is a strong clue that IgA-based antibody responses may be limited.
Why IgA matters for celiac testing
Many first-line celiac blood tests measure IgA antibodies (for example, tTG-IgA). If your total IgA is low, you may not produce enough IgA antibodies for those tests to turn positive even if celiac disease is present. In that situation, IgG-based tests (such as tTG-IgG or deamidated gliadin peptide IgG) are often used instead.
What do my IgA results mean?
Low IgA levels
Low IgA can be seen in selective IgA deficiency, which may show up as frequent respiratory or GI infections, or it may be found incidentally with no obvious symptoms. A low result can also make IgA-dependent tests (including some celiac antibody tests) less reliable, so your clinician may switch to IgG-based alternatives. If IgA is very low or undetectable, next steps often include checking other immunoglobulins (IgG and IgM) and reviewing your infection history and medication list.
Optimal (in-range) IgA levels
An in-range IgA suggests you have a typical capacity to produce this antibody class in the bloodstream. If you are doing a celiac workup, a normal total IgA makes IgA-based celiac antibodies easier to interpret. However, a normal IgA does not rule out immune dysfunction on its own, because immune problems can involve antibody quality, vaccine response, or other immune pathways not captured by a single total IgA measurement.
High IgA levels
High IgA usually reflects immune activation rather than “too much immunity.” It can occur with chronic infections, inflammatory or autoimmune conditions, and some liver diseases, and it may be seen alongside elevations in other inflammatory markers. Persistently high IgA may prompt your clinician to look for a pattern with other immunoglobulins and to evaluate symptoms, liver enzymes, and markers of inflammation rather than treating the number in isolation.
Factors that influence IgA
Your IgA level can shift with acute illness, chronic inflammation, and certain medications that affect the immune system. Age and genetics matter as well; some people naturally run low without frequent infections, while others have symptoms that track closely with their IgA level. Timing also matters for interpretation: if you test during an active infection or shortly after, repeating the test when you are well can clarify whether the finding is persistent.
What’s included
- Immunoglobulin A
Frequently Asked Questions
What does an IgA blood test measure?
It measures total immunoglobulin A (IgA) circulating in your blood (serum). This helps assess your ability to produce IgA antibodies and can support evaluation of recurrent infections or guide celiac disease testing strategy.
Do I need to fast for an IgA test?
Fasting is not usually required for a standalone serum IgA test. If IgA is ordered with other labs that do require fasting (such as lipids or glucose/insulin testing), follow the instructions for the full panel you are getting.
Can low IgA cause a false-negative celiac test?
Yes. If your total IgA is low, IgA-based celiac antibody tests (like tTG-IgA) may be negative even when celiac disease is present. In that situation, clinicians often use IgG-based celiac tests and may consider additional evaluation based on symptoms.
What is selective IgA deficiency?
Selective IgA deficiency is a condition where IgA is very low while other immunoglobulins may be normal. Some people have no symptoms, while others have recurrent respiratory or GI infections, allergies, or autoimmune conditions. Diagnosis and management should be guided by a clinician, often with additional immune testing.
What tests are commonly ordered with IgA?
IgA is often paired with IgG and IgM (an immunoglobulins panel) to look for broader patterns. For celiac evaluation, total IgA is commonly paired with celiac antibodies (such as tTG-IgA, and IgG-based tests if IgA is low). Your clinician may also consider vaccine response testing or other immune studies depending on your history.
What can cause high IgA levels?
High IgA can be associated with chronic inflammation, ongoing infection, autoimmune conditions, and some liver diseases. A single high result is usually interpreted alongside symptoms and other labs, and it may be repeated if there is concern it reflects a persistent pattern.