Tissue transglutaminase IgA (tTG-IgA) test
Quick answer: This test measures IgA antibodies against tissue transglutaminase, the main blood test used to look for coeliac disease. Doctors order it for long-term diarrhoea, bloating, weight loss, unexplained anaemia or a family history of coeliac disease.
- SampleBlood
- TakesAbout 5 minutes
- Before the testKeep eating your usual diet with gluten before the test unless your doctor advises otherwise, as stopping gluten can give a false negative.
How the test is done
- 1You keep eating foods with gluten, such as wheat, before the test
- 2Blood is drawn from your arm
- 3The lab measures tTG-IgA and often total IgA
- 4Results are reported as negative or positive, with a level
What your results can mean
Reading your report
A low total IgA level can cause a false negative, so labs may check it too; discuss your result with your doctor.
If the result is outside the usual range
A raised level can point to coeliac disease, and very high levels make it more likely. Low or negative results can occur with a gluten-free diet or IgA deficiency.
Who usually has this test
People with long-lasting diarrhoea, bloating, weight loss or iron-deficiency anaemia, or a family member with coeliac disease.
Risks and aftercare
Bruising is possible; do not start a gluten-free diet until your doctor has the result.
Names and options
Also called: tTG IgA, anti-tTG, coeliac disease test, celiac test
Listed by the hospital as
- TISSUE TRANSGLUTAMINASE IGA, SERUM
Questions about this test
How much gluten should I eat before the test?
Guidelines suggest eating some gluten in more than one meal every day for at least six weeks before testing. Do not start a gluten-free diet until testing is done.
Why is total IgA tested too?
Some people naturally make little IgA, which can make tTG-IgA falsely negative. If IgA is low, an IgG-based test is used instead.
Is coeliac disease common in India?
Yes, it is more common in north India, where wheat is a staple, but it is found across the country. Many people have mild or unusual symptoms.
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This page explains each test in general terms so you know what to expect. It is not medical advice: your doctor decides which tests you need and what your results mean. Reference ranges differ between laboratories. Updated 4 November 2026.