TL;DR — Bottom Line
- You must be eating gluten for the test to work. Coeliac serology detects the immune response to gluten. Remove gluten and the antibodies fall, often to normal, and the test becomes uninterpretable.
- tTG-IgA is the first-line test and must be paired with total IgA, because selective IgA deficiency is disproportionately common in coeliac disease and produces false negatives.
- Genetic testing rules out, it does not rule in. Almost everyone with coeliac carries HLA-DQ2 or DQ8, but so does a large minority of the general population who will never develop it.
- Diagnosis in adults is usually confirmed by duodenal biopsy. A positive home antibody test is a reason to see a gastroenterologist before changing your diet, not a reason to go gluten-free.
- Non-coeliac gluten sensitivity is a separate thing with no validated test. A negative coeliac panel does not mean gluten is fine for you; it means you do not have this specific autoimmune disease.
Quick Picks
Coeliac disease is an autoimmune condition in which gluten triggers immune-mediated damage to the small intestinal lining. It is not an allergy and it is not an intolerance, and the distinction matters clinically: untreated coeliac disease is associated with malabsorption, osteoporosis, iron deficiency and, in long-standing cases, a raised risk of certain malignancies.
It is also substantially underdiagnosed, and the rise of gluten-free eating has made that worse rather than better. Every person who removes gluten because they feel better without it, and then tests, gets an uninterpretable result. This page is largely about that problem, because it is the single thing that determines whether a test kit is worth buying at all.
Coeliac Tests and What Each One Does
| Test | What it measures | Use |
|---|---|---|
| tTG-IgA | IgA antibodies to tissue transglutaminase | First-line screening; high sensitivity and specificity |
| Total IgA | Overall IgA level | Essential companion — low IgA invalidates tTG-IgA |
| DGP-IgG | IgG to deamidated gliadin peptides | Useful when IgA is deficient, and in young children |
| EMA-IgA | Endomysial antibodies | Very high specificity; used to confirm ambiguous results |
| HLA-DQ2 / DQ8 | Genetic predisposition | Rules out if negative; nearly useless if positive |
| Duodenal biopsy | Villous architecture | Confirmatory standard in adults |
The Gluten Rule, Stated Plainly
Coeliac serology measures your immune system's ongoing reaction to gluten. If you are not eating gluten, that reaction subsides and antibody levels fall — frequently into the normal range within weeks to months. A negative test in someone on a gluten-free diet tells you nothing at all about whether they have coeliac disease.
The practical guidance from coeliac organisations is to be eating gluten regularly — commonly described as the equivalent of one to two slices of wheat bread a day — for at least six weeks before serological testing, and for a period before biopsy. If you have already removed gluten and feel dramatically better, reintroducing it for a gluten challenge is genuinely unpleasant, which is exactly why the order of operations matters: test first, then change the diet.
Why Total IgA Is Not Optional
The first-line test, tTG-IgA, measures an IgA-class antibody. Selective IgA deficiency — where a person produces little or no IgA — occurs in the general population at low frequency and is several times more common among people with coeliac disease. In someone with IgA deficiency, tTG-IgA will be low or negative regardless of whether they have coeliac disease, because they cannot mount the antibody being measured.
This is why any test kit worth buying measures total IgA alongside tTG-IgA. If total IgA is low, the testing switches to IgG-based assays such as DGP-IgG. A kit that offers tTG-IgA alone will silently produce false negatives in precisely the group most likely to have the disease.
What Genetic Testing Can and Cannot Do
Nearly all people with coeliac disease carry HLA-DQ2 or HLA-DQ8. That makes the test excellent at exclusion: if you carry neither, coeliac disease is highly unlikely and can generally be taken off the table permanently.
The reverse inference does not hold. A large minority of the general population carries one of these haplotypes and the overwhelming majority of them will never develop coeliac disease. A positive genetic test therefore tells you almost nothing about whether you have it. Its genuine uses are ruling out in family members, and resolving the situation of someone already gluten-free who cannot face a gluten challenge — a negative result ends the question without one.
Home Testing and Where It Fits
Home coeliac antibody kits fall into two groups. Mail-in kits collect a blood sample and send it to a laboratory running the same assays a clinician would order, which is genuinely useful. Rapid point-of-care strips give an immediate qualitative result and are considerably less reliable, particularly at low antibody levels, and they usually do not measure total IgA.
Either way, the home test is a screening step. Diagnosis in adults is normally confirmed by duodenal biopsy, because a raised antibody level has other causes and because the biopsy establishes the degree of damage as a baseline. A positive home result means see a gastroenterologist while still eating gluten — not start a gluten-free diet, which will make the confirmatory biopsy harder to interpret.
If the Test Is Negative and You Still React to Wheat
This is common and it is not a contradiction. Non-coeliac gluten sensitivity describes people who reliably report symptoms on gluten-containing food without coeliac serology or the intestinal damage. It is a recognised clinical entity with no validated biomarker, so it remains a diagnosis of exclusion.
There is also a strong case that a proportion of these reactions are to fructans rather than gluten. Fructans are fermentable carbohydrates abundant in wheat and are high-FODMAP, and controlled challenge studies have found some people who identify as gluten-sensitive react to fructans and not to purified gluten. Practically, if you test negative for coeliac and still react to bread, a structured low-FODMAP trial supervised by a dietitian is a more informative next step than assuming gluten is the culprit.
Test Types Worth Considering
Ordered by how closely each matches what a clinician would request. The determining factor is not brand but which antibodies are measured, and whether total IgA is included.
tTG-IgA With Total IgA Mail-In Panel
The combination clinical guidelines specify as first-line: tissue transglutaminase IgA for the antibody response, and total IgA to confirm you can actually produce the antibody being measured. Sent to a laboratory rather than read on a strip at home, which matters for quantitative results. Confirm you have been eating gluten regularly for at least six weeks before sampling.
Who it is for: anyone investigating coeliac disease who is currently eating gluten and wants the test a clinician would order.
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Shop Celiac tTG-IgA Home Test Kits on AmazonComprehensive Coeliac Serology Panel
Adds deamidated gliadin peptide antibodies and, in some panels, endomysial antibodies to the first-line pair. The additional tests earn their place in specific situations: IgA deficiency, young children, and ambiguous borderline tTG results where high-specificity confirmation changes what happens next. For a straightforward first test it is more than most people need.
Who it is for: people with a borderline previous result, known IgA deficiency, or a strong family history wanting the fullest picture.
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Shop Comprehensive Celiac Antibody Panels on AmazonHLA-DQ2 and DQ8 Genetic Test
Tests for the genetic predisposition rather than the active disease, which makes it a rule-out tool. A negative result effectively excludes coeliac disease for life and is genuinely valuable — particularly for someone already gluten-free who would otherwise need a gluten challenge, and for first-degree relatives of a diagnosed patient. A positive result is common in the general population and means little on its own.
Who it is for: people already on a gluten-free diet who cannot face a gluten challenge, and relatives of diagnosed coeliacs.
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Shop Celiac HLA-DQ2 DQ8 Genetic Test Kits on AmazonIron, Ferritin, B12 and Vitamin D Panel
Untreated coeliac disease damages the small intestine where iron, folate, B12 and fat-soluble vitamins are absorbed, so deficiency in these is both a common presenting sign and a reason to test for coeliac in the first place. Worth running alongside serology, and worth rechecking after a period on a gluten-free diet to confirm absorption has recovered.
Who it is for: anyone with unexplained iron deficiency or fatigue, and newly diagnosed coeliacs establishing a baseline.
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Shop Iron B12 and Vitamin D Home Test Panels on AmazonCertified Gluten-Free Pantry Staples
Relevant only after a confirmed diagnosis, at which point the treatment is a strictly gluten-free diet for life — not a reduction. Certification standards specify a maximum gluten content, which matters because cross-contamination in shared facilities is the most common cause of ongoing symptoms in people who believe they are compliant. Oats are a specific case: they need to be certified gluten-free, as standard oats are frequently contaminated in processing.
Who it is for: people with a confirmed diagnosis; there is no reason to buy these before testing.
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Shop Certified Gluten-Free Pantry Staples on AmazonWhich One Fits Your Situation
The order of operations is the whole thing. Test while eating gluten, confirm with a clinician before changing the diet, and only then commit to gluten-free eating — which for a confirmed coeliac is a lifelong medical treatment rather than a preference.
If you have already removed gluten and improved, the genetic test is the graceful exit: a negative result closes the question permanently, and a positive one at least tells you a gluten challenge would be worth the discomfort.