What is tTG-IgA?
Coeliac disease is an autoimmune disease in which the immune system reacts to gluten, the protein in wheat, rye and barley. In that reaction antibodies arise against tissue transglutaminase, an enzyme in your own gut wall, and the gut wall becomes inflamed and flattens, so nutrients are absorbed less well. tTG-IgA measures those antibodies, of the IgA kind, the antibody of the mucous membranes. The test is good: in anyone who eats gluten and has a normal IgA, it finds the great majority of people with coeliac disease, and a clearly positive result is almost always coeliac disease. It has two conditions. The antibodies are only made as long as gluten comes in, so anyone already eating gluten-free tests negative without that meaning anything. And because it is an IgA antibody, anyone who makes little IgA themselves always tests negative; that is why total IgA belongs with it as standard. Your report shows tTG-IgA as a number with a limit: below 7 kU/L normal, above 10 kU/L positive, and in between equivocal. The unit differs per lab; the limit is the same everywhere. The higher above the limit, the more certain the result.
Why is tTG-IgA relevant?
Coeliac disease occurs in about one in a hundred people, and most of them do not know it. The complaints are often vague: tiredness, a bloated belly, changeable stools, an iron deficiency that will not go away, osteoporosis at a young age, or no complaints at all. Untreated, the disease damages the gut wall for years, with deficiencies of iron, vitamin B12, folate and vitamin D as the result, and an increased chance of fractures and other autoimmune diseases. The treatment is not a medicine but a diet: lifelong gluten-free, after which the gut wall recovers and the deficiencies disappear. That makes coeliac disease a disease worth knowing about, and tTG-IgA the test that makes that possible. Anyone with an iron deficiency that does not respond to iron, anyone with a parent or sibling with coeliac disease, anyone with type 1 diabetes or an autoimmune thyroid disease has good reason to have it measured. The pitfall is the order. Many people who feel better without gluten have already gone gluten-free before being tested. Then the antibodies are gone and the test measures nothing, and the question of whether it was coeliac disease, or a sensitivity without autoimmune disease, stays open. Anyone who wants to know eats normal gluten first for at least six weeks, daily, and tests after that.
tTG-IgA reference ranges
What counts beside the number:
- Whether you ate gluten daily in the weeks before the test; without gluten the test measures nothing
- Your total IgA, because with a deficiency you always test negative
- How far the value sits above the limit: many times the limit is almost certainly coeliac disease
- Ferritin, vitamin B12, folate and vitamin D, the deficiencies coeliac disease causes
- Coeliac disease in the family, type 1 diabetes or an autoimmune thyroid disease, which raise the chance
- Complaints: tiredness, a bloated belly, changeable stools, an iron deficiency that will not go away
The rows above are limits, not normal values, and the limit is the same in the national agreement and at the labs; only the unit differs per lab. One lab runs the test without publishing a limit beside it. The test measures an IgA antibody, so a negative result needs a normal total IgA: anyone who makes too little IgA always tests negative and has an increased chance of coeliac disease.
What Dutch labs actually use
Of these four antibody pages this is the only one where the labs and a Dutch guideline land on the same figure. Star-shl cuts the scale into three steps: negative below 7.0, equivocal from 7.0 to 10.0 and positive above 10.0. Certe runs its band from 0 to 7 and Clinical Diagnostics prints below 7. The limit of 7 is therefore the same at all three, and the Dutch primary-care laboratory agreement names exactly those three steps. Unilabs does carry the determination, but prints no reference value beside it: the field is empty and the unit reads n.v.t., not applicable. This page therefore sets three tables side by side rather than four. The unit they each write differently. Star-shl writes U/ml, Certe arb'U/mL and Clinical Diagnostics E/ml, where the guideline holds kU/L. Four notations, the same two figures.
0 – 7kU/L
Above this limit every lab calls it raised.
From 0 – 7 kU/L no lab calls it raised. Above that every lab calls it raised.
Every age, per lab
| Laboratory | Group | Reference range |
|---|---|---|
| Star-shl2026 | Negative | < 7.0 kU/LDecision limit |
| Equivocal | 7.0–10.0 kU/LDecision limit | |
| Positive | > 10.0 kU/LDecision limit | |
| Certe2026 | All ages | 0–7 kU/LDecision limit |
| Clinical Diagnostics2026 | All ages | < 7 kU/LDecision limit |
Each band as the lab publishes it, retrieved in 2026, unless marked otherwise.
tTG-IgA high or low: what it means
A positive tTG-IgA, above 10 kU/L, fits coeliac disease strongly; the higher, the more certain, and a value many times the limit is enough for the diagnosis in children. In adults the diagnosis is usually confirmed with an endoscopy of the small intestine, and that is done while you are still eating gluten. A slightly raised value sometimes occurs without coeliac disease, with type 1 diabetes, an autoimmune thyroid disease or a liver disease, and is then repeated and supplemented with a second antibody. A negative tTG-IgA is reliable if you ate gluten in the weeks before and your total IgA is normal. If you were already gluten-free, the result says nothing; if your IgA is low, an IgG variant of the test is used. In a small share of people with coeliac disease the test still stays negative, and with strong suspicion an endoscopy follows anyway. What you do about it: with a confirmed diagnosis eating gluten-free is the whole treatment, and the antibodies then fall to normal in months to a year; the test is used afterwards to see whether the diet is working. Without a diagnosis eating gluten-free is no health gain and is a restriction: most people without coeliac disease gain nothing from it, and anyone who still wants the test forfeits the chance to read it. TTG-IgA belongs beside your total IgA, and with complaints beside ferritin, vitamin B12, folate and vitamin D, the deficiencies coeliac disease causes.
What lowers it
Negative is the ordinary outcome, provided the test could measure anything.
| Cause | How often |
|---|---|
| A gluten-free diet before the drawThe antibodies are only made as long as gluten comes in; anyone already eating gluten-free tests negative without that meaning anything | Often |
| An IgA deficiencyThe test measures an IgA antibody; anyone who makes little IgA themselves always tests negative and has an increased chance of coeliac disease, so then an IgG variant is used | Sometimes |
What raises it
Almost always coeliac disease; slightly raised sometimes something else.
| Cause | How often |
|---|---|
| Coeliac diseaseThe immune system reacts to gluten and makes antibodies against an enzyme of your own gut; the higher the value, the more certain, and after a gluten-free diet it falls back to normal | Often |
| A slightly raised value without coeliac diseaseWith type 1 diabetes, an autoimmune thyroid disease or a liver disease the value can sit just above the limit; then the test is repeated and supplemented with a second antibody | Sometimes |
How does a tTG-IgA blood test work?
- Referral
- Not needed. You can have the test done yourself; a positive result is confirmed afterwards before you start eating gluten-free.
- Eating gluten
- Yes, and that is the most important condition: at least six weeks of daily gluten, for instance a few slices of bread, before the test. Anyone already eating gluten-free has to go back to gluten first to make the test readable.
- Fasting
- Not needed.
- The draw
- One tube of blood from a vein in your arm, with total IgA from the same tube.
- The result
- A single number with a limit: below 7 kU/L normal, above 10 kU/L positive, in between equivocal. The unit differs per lab, the limit does not.
- Repeating
- An equivocal result after a few months, with gluten in the diet. After the diagnosis the test is used to see whether the gluten-free diet is working: the antibodies then fall to normal in months to a year.
- Where to draw
- You can draw at 250+ locations near you, no referral needed. See the locations
Frequently asked questions
What is tTG-IgA?
IgA antibodies against tissue transglutaminase, an enzyme in your own gut wall. In coeliac disease the immune system reacts to gluten and makes antibodies against that enzyme, while the gut wall becomes inflamed and flattens. This test looks for those antibodies and is the first step of an investigation for coeliac disease. Because it is an IgA antibody, your total IgA belongs with it.
What is a normal tTG-IgA level?
There is no normal value, only a limit, and that is the same everywhere: below 7 kU/L normal, above 10 kU/L positive, in between equivocal. The unit differs per lab. A normal result is reliable if you ate gluten in the weeks before and your total IgA is normal.
What does a positive tTG-IgA mean?
That coeliac disease is likely; the higher the value, the more certain, and a value many times the limit is enough for the diagnosis in children. In adults the diagnosis is usually confirmed with an endoscopy of the small intestine, while you are still eating gluten. A slightly raised value sometimes occurs without coeliac disease, with type 1 diabetes, a thyroid disease or a liver disease, and is then repeated.
What does a negative tTG-IgA mean?
Usually that you do not have coeliac disease, provided the test could measure anything: you ate gluten in the weeks before and your total IgA is normal. If you were already gluten-free, the result says nothing; if your IgA is low, an IgG variant of the test is used. In a small share of people with coeliac disease the test stays negative, and with strong suspicion an endoscopy follows anyway.
Do I have to eat gluten before the test?
Yes, and that is the most important condition. The antibodies are only made as long as gluten comes in. Eat gluten daily for at least six weeks, for instance a few slices of bread, before you test. Anyone already eating gluten-free who wants to know whether it is coeliac disease has to go back to gluten first; that is unpleasant if it gives you complaints, but without it the question cannot be answered.
I feel better without gluten; do I have coeliac disease?
That can only be answered with this test if you eat gluten again. Feeling better without gluten also happens without coeliac disease, for instance from an irritable bowel or from the fibres and sugars in wheat, and then eating gluten-free is a choice and not a treatment. Coeliac disease is an autoimmune disease that damages the gut wall and causes deficiencies, and it calls for a strict and lifelong diet. The difference is worth knowing.
Why does my total IgA belong with it?
Because the test measures an IgA antibody. Anyone who makes little IgA themselves, and that is about one in six hundred people, always tests negative, even with coeliac disease, and has an increased chance of the disease. Total IgA therefore says whether the test could measure anything; with a deficiency an IgG variant is used.
Do I need to fast?
No. What counts is that you ate gluten in the weeks before, and that your total IgA is determined in the same draw.
Which tests include tTG-IgA?
tTG-IgA is measured in the Autoimmunity & coeliac module, on top of another draw. It is not orderable yet.
Related biomarkers
Sources
- 1.Star-shl, test catalogue (Dutch): anti-transglutaminase IgA (anti-tTG). 2026. star-shl.nl
- 2.Certe, test catalogue (Dutch): anti-tTG IgA. 2026. bepalingenwijzer.certe.nl
- 3.Clinical Diagnostics, lab guide (Dutch): coeliac disease (anti-tTG IgA). 2026. clinicaldiagnostics.nl
- 4.Unilabs, test catalogue (Dutch): anti-transglutaminase IgA. 2026. bepalingenklapper.nl
- 5.LESA Laboratory diagnostics (Dutch primary-care laboratory agreement). 2026. richtlijnen.nhg.org
Educational information only, not medical advice. Consult a healthcare professional for clinical decisions.
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tTG-IgA is measured in the Autoimmunity & coeliac module, on top of another draw. It is not orderable yet.
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