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BioSignal
Condition

Coeliac Disease

An autoimmune disease — and do not go gluten-free before you are tested

Last reviewed
July 2026
Version
1.0
Review cadence
Annually

What it is

Coeliac disease is an autoimmune condition in which gluten triggers the immune system to attack the lining of the small intestine, flattening the villi that absorb nutrients. It is NOT an allergy and it is NOT an intolerance — those are different mechanisms with different consequences, and the distinction is not pedantry. It affects around 1 in 100 people, and the MAJORITY REMAIN UNDIAGNOSED, in large part because most people with coeliac disease do not present with the diarrhoea and weight loss the textbooks describe. They present with iron deficiency that will not resolve, with unexplained fatigue, with early osteoporosis, with abnormal liver tests, with mouth ulcers, with infertility — or with nothing at all.

Why it matters

Because the single most common thing people do when they suspect gluten is a problem is the one thing that makes it impossible to diagnose. THE TESTS FOR COELIAC DISEASE ONLY WORK IF YOU ARE STILL EATING GLUTEN. Go gluten-free first, feel better, and the antibody test and the biopsy both turn negative — and you are left with a lifelong question that can now only be answered by eating gluten again for weeks, deliberately, until you are ill enough to be tested. People do this in good faith, on the advice of the internet, and it costs them a diagnosis. And a diagnosis matters: untreated coeliac disease causes osteoporosis, persistent iron deficiency, subfertility, and a small increase in small-bowel lymphoma. 'Gluten-free because it agrees with me' and 'gluten-free because I have an autoimmune disease' are not the same thing, and only one of them requires being strict about cross-contamination for life.

The evidence

What BioSignal knows about treating this

Guideline-anchored clinical contextLast reviewed July 2026 · reviewed annually · 4 references

What works for Coeliac Disease

BioSignal’s clinical summary, most important first.

  1. GET TESTED BEFORE YOU CUT GLUTEN OUT — not after. Going gluten-free first is the commonest and most costly mistake in this area, and it is made by people acting reasonably on bad advice
  2. If you are already gluten-free and want a diagnosis, a formal gluten challenge is needed — several weeks of eating gluten. Discuss it with a clinician rather than attempting it alone
  3. A STRICT, LIFELONG GLUTEN-FREE DIET is the treatment, and 'strict' is doing real work: for coeliac disease, cross-contamination matters, and a little gluten is not fine. This is not the same as the gluten-free choices made by people without the disease
  4. Referral to a dietitian — this is a genuinely difficult diet to do properly, and doing it badly leaves people both symptomatic and nutritionally worse off
  5. Correct the deficiencies — iron, vitamin D, calcium, B12 and folate are commonly depleted at diagnosis and need actively treating, not just time
  6. Bone density assessment — osteoporosis is frequently present at diagnosis and is preventable thereafter
  7. Test first-degree relatives — around 1 in 10 will have it, and many will have no symptoms at all
  8. Annual review, with antibody levels used to monitor adherence

Signal Records relevant to this condition

Interventions and contributing factors — some of these records describe a cause rather than a cure. The rating shown is BioSignal’s confidence in that Signal Record, not a claim about how well it treats this condition. Open any of them for the full evidence.

Start Here

New to this? Read these first

  1. FoundationGut Health & The MicrobiomeWhat actually improves gut health — and why fibre beats the supplements people buy.
  2. BiomarkerFerritinIron stores — with an inflammation caveat
  3. Signal RecordVitamin DCholecalciferol (Vitamin D₃)
  4. Body SystemDigestiveGut health, the microbiome, and nutrient absorption.
  5. ConditionIron Deficiency & AnaemiaThe commonest nutritional deficiency in the world — and a finding that always has a cause
Typical Journey

How this usually unfolds

  1. Recognize risk factors
  2. Get diagnosed
  3. Track key biomarkers
  4. Lifestyle first
  5. Evidence-based treatment
  6. Long-term monitoring

An orientation to how this topic is typically approached — not medical advice.

Who is at risk

  • A first-degree relative with coeliac disease — around a 1 in 10 risk, and a reason to be tested even without symptoms
  • Type 1 diabetes
  • Autoimmune thyroid disease
  • Other autoimmune conditions
  • Down syndrome and Turner syndrome
  • Selective IgA deficiency — which also causes FALSE NEGATIVE coeliac antibody tests, so it must be checked at the same time

How it's diagnosed

Diagnosis rests on serology and, usually, biopsy — and both require that you are EATING GLUTEN at the time, which is the point on which most self-directed investigation founders. The first-line test is tissue transglutaminase IgA (tTG-IgA), and it must be accompanied by a TOTAL IgA level, because selective IgA deficiency is common in coeliac disease and produces a falsely reassuring result. A positive test is followed by duodenal biopsy in adults. In children with very high antibody levels, biopsy can sometimes be avoided. If you have already gone gluten-free, a formal gluten challenge — typically several weeks of eating gluten daily — is required before testing, and it is exactly as unpleasant as it sounds.

  • DO NOT START A GLUTEN-FREE DIET BEFORE TESTING — this is the single most important practical instruction on this page. It makes the tests negative and the diagnosis unobtainable
  • Tissue transglutaminase IgA (tTG-IgA) — the first-line antibody test
  • TOTAL IgA — must be measured alongside, because IgA deficiency produces a false negative tTG
  • Duodenal biopsy at endoscopy — confirms villous atrophy in adults
  • Ferritin and full blood count — unexplained iron deficiency is one of the commonest presentations, and a reason to test for coeliac disease in its own right
  • Vitamin D, calcium, B12 and folate — malabsorption is the mechanism
  • Bone density scan at diagnosis — osteoporosis is common and often already present
  • Testing of first-degree relatives — around a 1 in 10 risk
Most important

Key biomarkers

FerritinVitamin D (25-OH)Vitamin B12FolateALTHigh-Sensitivity CRP
Day to day

Lifestyle

  • Gluten-free means gluten-free: wheat, barley and rye, including cross-contamination from shared toasters, fryers and chopping boards
  • Oats are contaminated in most supply chains — use certified gluten-free oats, and a minority of people react to oats themselves
  • Gluten-free processed foods are frequently lower in fibre and higher in sugar and fat than what they replace. Base the diet on naturally gluten-free whole foods, not on the free-from aisle
  • Watch the fibre: a badly-constructed gluten-free diet is a common cause of new constipation
Explore

Explore this condition across BioSignal

Related Foundations

Gut Health & The MicrobiomeNutritionFiber

Related Signal Records

Vitamin DProbioticsPsyllium

Related body systems

DigestiveImmuneBone

Related conditions

Iron Deficiency & AnaemiaAutoimmune DiseaseIrritable Bowel SyndromeInflammatory Bowel DiseaseOsteoporosisHypothyroidismType 2 DiabetesFatigueInfertilityChronic Low-Grade Inflammation

Frequently asked questions

Should I try going gluten-free to see if it helps?

NO — not before you are tested, and this is the single most important thing on this page. The tests for coeliac disease work by detecting your immune system's reaction TO GLUTEN. Remove the gluten and the reaction fades, the antibody test turns negative, and the biopsy heals — so you can feel much better and be untestable at the same time. If you then want a diagnosis, you have to eat gluten again for several weeks, deliberately, until you are ill enough to test. People make this mistake constantly, in good faith, and it costs them the answer. Get tested first. It takes a blood test.

What is the difference between coeliac disease, wheat allergy, and gluten intolerance?

Three different things, and conflating them is why this area is such a mess. COELIAC DISEASE is autoimmune: gluten triggers your immune system to damage your small intestine. The damage is real, it is measurable, and it happens whether or not you feel symptoms. WHEAT ALLERGY is an IgE allergic reaction — immediate, and potentially anaphylactic. NON-COELIAC GLUTEN SENSITIVITY is the third, and BioSignal will be honest about it: people genuinely do report symptoms with gluten in the absence of coeliac disease or allergy, the symptoms are real, and the mechanism is not understood — some of it may be FODMAPs in wheat rather than gluten itself. It causes no intestinal damage and no autoantibodies. It is real, and it is not coeliac disease, and the practical difference is enormous: coeliac disease requires lifelong strictness about crumbs; sensitivity does not.

I don't have diarrhoea. Can I still have coeliac disease?

Very much so, and this is why most cases are missed. The classic picture — diarrhoea, weight loss, malabsorption — is now the minority presentation. Far more people present with iron deficiency that keeps coming back, unexplained fatigue, osteoporosis at an unexpected age, abnormal liver enzymes, recurrent mouth ulcers, an itchy blistering rash (dermatitis herpetiformis), tingling in the hands and feet, or subfertility. Some have no symptoms at all and are found through family screening. If you have iron deficiency with no obvious cause, coeliac disease is one of the specific things worth testing for.

Is gluten-free healthier for everyone?

No, and there is no good evidence that it is. For the roughly 1% of people with coeliac disease it is essential and non-negotiable. For everyone else, cutting out gluten offers no established health benefit — and gluten-free PROCESSED foods are frequently lower in fibre and higher in sugar and fat than the products they replace. Wholegrain wheat, rye and barley are, for people who can eat them, associated with good health outcomes. Removing an entire food group because it has been marketed as harmful is not a neutral act.

What happens if I cheat occasionally?

For coeliac disease, more than people are told. Each exposure triggers the immune response and damages the intestinal lining, and this happens whether or not you feel it — some people with coeliac disease get no symptoms from gluten at all, which makes it easy to believe that the occasional lapse is harmless. It is not: ongoing damage means ongoing malabsorption, and the long-term consequences are osteoporosis, persistent iron deficiency, and a small increase in small-bowel lymphoma. This is the crucial practical difference between coeliac disease and gluten sensitivity, and it is worth being clear-eyed about.

Evidence summary

Coeliac disease is an immune-mediated enteropathy triggered by gluten in genetically susceptible individuals (HLA-DQ2/DQ8), with a population prevalence around 1% and a majority of cases undiagnosed. Serological testing with tissue transglutaminase IgA, interpreted alongside total IgA, is the first-line investigation and is confirmed by duodenal biopsy in adults; both are dependent on continued gluten ingestion, and initiating a gluten-free diet before testing renders diagnosis unobtainable without a formal gluten challenge. The classical malabsorptive presentation is now a minority; iron deficiency anaemia, fatigue, osteoporosis, transaminitis and subfertility are common presentations, and unexplained iron deficiency is an established indication for coeliac serology. Treatment is a strict lifelong gluten-free diet, which reverses villous atrophy and reduces the risks of osteoporosis, persistent malabsorption and small-bowel lymphoma. First-degree relatives carry roughly a 1 in 10 risk. Non-coeliac gluten sensitivity is a distinct entity in which symptoms are reported without autoantibodies or enteropathy; its mechanism is unresolved and may in part reflect FODMAPs rather than gluten. There is no evidence that a gluten-free diet benefits people without coeliac disease or wheat allergy.

References & sources

  • NICE NG20 — Coeliac disease: recognition, assessment and management
  • ESPGHAN guidelines for diagnosing coeliac disease in children and adolescents
  • British Society of Gastroenterology guidelines on coeliac disease
  • Studies of coeliac serology performance and the effect of a gluten-free diet on test accuracy

Educational information — not medical advice

Condition pages orient you across the evidence; they don't diagnose or treat. Diagnosis and management belong with a qualified clinician. See our Medical Disclaimer.

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