Understanding Your Celiac Disease Testing

Section Editor: Christopher McCudden Ph.D., DABCC, FADLM, FCACB
July 10, 2026

Celiac disease is an autoimmune condition in which eating gluten, a protein found in wheat, barley, and rye, triggers the immune system to damage the lining of the small intestine. Celiac disease testing refers to a group of blood tests that detect antibodies produced in response to this immune reaction. These tests are used to decide who is likely to have celiac disease and should go on to have the diagnosis confirmed, which in most cases is done with a biopsy of the small intestine.

This article explains what celiac disease blood tests look for and what each result means. It also covers two points that are easy to miss but change everything: the tests are only accurate while you are still eating gluten, and a positive blood test usually needs to be confirmed before a diagnosis is made.

The reference range that applies to your result is the one printed on your laboratory report, not the typical ranges shown here. Reference ranges vary between laboratories based on the equipment used, the population tested, and individual factors such as age, sex, and pregnancy status. Always compare your result to the reference range printed on your own report, and discuss any abnormal result with your doctor.

What does celiac disease testing look for?

Celiac disease testing looks for autoantibodies, which are antibodies the immune system makes against the body’s own tissues. In celiac disease, eating gluten triggers the immune system to produce specific antibodies, which can be measured in a blood sample. The most useful of these antibodies is directed against an enzyme called tissue transglutaminase. Because these antibodies are produced only when the immune system is actively reacting to gluten, the tests only work while a person is still eating gluten regularly.

How is the test performed?

Celiac disease testing is done on a blood sample drawn from a vein, without any special preparation. The single most important point is that you must be eating a normal, gluten-containing diet for the test to be accurate. If gluten has already been removed from the diet, antibodies fall and the intestine begins to heal, so tests can be falsely negative. For this reason, it is best not to start a gluten-free diet until testing is complete. Testing is usually done in a set order: a first-line antibody test is measured along with a total IgA level, and additional tests are added as needed.

What do the blood test results mean?

The tests below are the ones most often used to investigate celiac disease. Your report may include one or several of them.

Anti-tissue transglutaminase IgA (anti-tTG IgA)

This is the main first-line test for celiac disease. It measures IgA antibodies against tissue transglutaminase and is both sensitive and specific, meaning it detects most people with celiac disease while producing relatively few false positives. A positive result strongly suggests celiac disease and is usually followed by a confirmatory step. A very high level, several times above the upper limit of normal, makes celiac disease especially likely.

Total IgA

This test measures the overall amount of IgA antibody in the blood and is checked because a small number of people produce little or no IgA, a condition called IgA deficiency. In these people, the IgA-based celiac tests, including anti-tTG IgA, can be falsely negative. If the total IgA level is low, the laboratory switches to IgG-based versions of the tests, such as anti-tTG IgG or deamidated gliadin peptide IgG, which do not depend on IgA.

Anti-endomysial antibody (EMA)

The endomysial antibody (EMA) test is one of the most specific tests for celiac disease, meaning that a positive result almost always indicates the disease is present. It takes more time and skill to perform than the anti-tTG test, so it is generally used to confirm a positive anti-tTG result rather than as the first test. A positive EMA adds strong support to the diagnosis.

Deamidated gliadin peptide (DGP) antibodies

Deamidated gliadin peptide (DGP) antibodies, measured as IgA or IgG, are directed against a processed form of gluten. They are most useful in two situations: in young children, in whom the anti-tTG test is sometimes less reliable, and in people with IgA deficiency, in whom the IgG version is helpful. DGP antibodies have replaced an older test for antibodies against gliadin, which is no longer recommended because it was less accurate.

HLA-DQ2 and DQ8 genetic testing

Almost everyone with celiac disease carries one of two inherited genetic markers, called HLA-DQ2 and HLA-DQ8. A blood test can check for these markers, but it is used differently from the antibody tests. Because a negative result means celiac disease is very unlikely, this test is most useful for ruling the disease out. It cannot confirm the diagnosis, however, because these markers are also common in people who will never develop celiac disease. Genetic testing is especially helpful when a person has already started a gluten-free diet, which makes the antibody tests unreliable; when the antibody results are unclear; or when screening people at higher risk, such as the close relatives of someone with celiac disease.

What can affect the results?

Several factors change the accuracy of celiac disease testing, which is why the results are always interpreted in context. The most important factor is diet: following a gluten-free or reduced-gluten diet before testing lowers antibody levels and allows the intestine to heal, which can produce a falsely negative result. IgA deficiency can also cause a false-negative result with IgG-based tests, which is why total IgA is measured at the same time. In very young children, the antibody tests are somewhat less reliable, so DGP testing may be added. Finally, damage to the lining of the small intestine is not unique to celiac disease and can also be caused by infections, some medications, and other inflammatory conditions, so the antibody results and the biopsy are interpreted together rather than in isolation.

What happens after celiac disease testing?

A positive celiac antibody test guides the next steps rather than serving as the final diagnosis. In most adults, a positive result leads to referral to a gastroenterologist and a biopsy of the small intestine, in which small tissue samples are examined under the microscope for the changes of celiac disease, including villous atrophy (flattening of the tiny finger-like projections that absorb nutrients). In children with a very high anti-tTG level confirmed by a positive endomysial antibody test, the diagnosis can sometimes be made without a biopsy. If testing is negative but celiac disease is still suspected, the doctor will consider whether a gluten-free diet or IgA deficiency affected the result. Because celiac disease can run in families, close relatives may also be offered testing, and because it can cause nutrient deficiencies, tests such as an iron panel may be checked. A gluten-free diet should be started only after the diagnosis has been confirmed, so that testing is not affected.

Questions to ask your doctor

Which celiac disease tests were done, and what were my results?
Was my total IgA level checked, and was it normal?
Was I eating enough gluten when the test was done for the result to be reliable?
Do I need a biopsy of the small intestine to confirm the diagnosis?
Should I keep eating gluten until all testing is complete?
If my test was negative but I still have symptoms, what are the next steps?
Would genetic (HLA) testing be helpful in my situation?
Do I have any nutrient deficiencies, such as low iron, that need treatment?
Should my close family members be tested for celiac disease?
Once I am diagnosed, how will my response to a gluten-free diet be monitored?