Coeliac Disease
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Coeliac Disease: Symptoms, Testing and Treatment
An autoimmune condition, not an intolerance — who should be tested, why the diet must wait until after testing, and what untreated coeliac disease costs.
Key fact: Do not go gluten-free before you are tested. Coeliac blood tests and the biopsy are only accurate while you are still eating gluten — NICE advises eating gluten in more than one meal every day for at least six weeks before testing. Cutting it out first is the single commonest reason a diagnosis is missed or delayed for years.
What coeliac disease is
Coeliac disease is an autoimmune condition. In someone who has it, gluten — a protein in wheat, barley and rye — triggers the immune system to attack the lining of the small intestine. The finger-like projections that absorb nutrients flatten, and absorption fails.
That mechanism explains the pattern of the illness. Some people present with obvious bowel symptoms; many present instead with the consequences of not absorbing things properly — iron deficiency anaemia, fatigue, bone thinning, unexplained weight loss — and never had dramatic gut problems at all.
Not an allergy, and not an intolerance
| Coeliac disease | Wheat allergy | Gluten sensitivity | |
|---|---|---|---|
| Mechanism | Autoimmune — the immune system damages the gut lining | Allergic reaction to wheat proteins | Not established; no antibodies, no gut damage |
| Timing | Over days to years | Usually within seconds or minutes | Hours |
| Gut damage | Yes | No | No |
| Diagnostic test | Blood antibodies, then biopsy | Allergy testing | No specific test exists |
| Consequences of ignoring it | Anaemia, osteoporosis, subfertility, rarely small bowel lymphoma | Anaphylaxis in severe cases | Symptoms only |
The distinction matters practically as well as semantically: a trace of gluten does real damage in coeliac disease even without symptoms, which is not true of gluten sensitivity. The full comparison sets it out.
Symptoms
Gut symptoms
Diarrhoea, sometimes particularly unpleasant-smelling; bloating and wind; abdominal pain; indigestion; constipation.
Absorption problems
Iron, B12 or folate deficiency; tiredness that does not resolve; unintentional weight loss; faltering growth in children.
Beyond the gut
Mouth ulcers that are severe or keep coming back; dental enamel defects; nerve symptoms; joint pain.
Skin
Dermatitis herpetiformis — an intensely itchy blistering rash, typically on elbows, knees and buttocks, which is coeliac disease showing in the skin.
Reproductive
Subfertility, recurrent miscarriage, and pregnancy complications including low birth weight.
Nothing obvious
Some people have no symptoms they would have mentioned, and are found through screening because a relative has it.
Who should be tested
NICE sets out who should be offered testing:
- Persistent unexplained abdominal or gastrointestinal symptoms
- Faltering growth in children
- Prolonged fatigue
- Unexpected weight loss
- Severe or persistent mouth ulcers
- Unexplained iron, vitamin B12 or folate deficiency
- Type 1 diabetes, at diagnosis
- Autoimmune thyroid disease, at diagnosis
- Irritable bowel syndrome in adults — because coeliac can mimic IBS exactly
- First-degree relatives of someone with coeliac disease
And who should be considered for it: metabolic bone disorders, unexplained neurological symptoms, subfertility or recurrent miscarriage, persistently raised liver enzymes, dental enamel defects, Down's syndrome and Turner syndrome.
The IBS overlap is the one worth dwelling on. Coeliac disease and IBS can look identical from the outside, which is why coeliac serology belongs in the initial workup of anyone being assessed for IBS in adulthood — not after a year of dietary experiments.
How it is diagnosed
| Stage | What happens |
|---|---|
| Blood test | Total IgA and IgA tissue transglutaminase (tTG) are the first-choice tests in young people and adults. IgA endomysial antibodies (EMA) are used if the tTG result is weakly positive |
| If you are IgA deficient | IgG-based tests are used instead — IgG EMA, IgG deamidated gliadin peptide (DGP) or IgG tTG — which is why total IgA is measured alongside |
| Referral | A positive blood test means referral to a gastrointestinal specialist for endoscopic intestinal biopsy, which confirms the diagnosis |
| Genetic testing | HLA DQ2/DQ8 testing is not used for initial diagnosis outside specialist settings |
A negative blood test with continuing symptoms is not necessarily the end of it — it is possible to have coeliac disease without detectable antibodies, and referral may still be appropriate. Getting tested covers the process in detail.
Why you must keep eating gluten
Both the blood test and the biopsy detect the response to gluten. Remove gluten and the antibodies fall and the gut lining heals, so the tests return to normal whether or not you have the condition. NICE advises anyone on a normal diet to eat gluten in more than one meal every day for at least six weeks before testing, and not to start a gluten-free diet until a specialist has confirmed the diagnosis.
This is the point at which most diagnoses are lost. Someone feels better without bread, concludes they are "a bit gluten intolerant", and years later cannot be tested without going back on gluten for six weeks — which, having felt better, almost nobody wants to do. The result is a lifetime of dietary restriction without the diagnosis, the monitoring, the family screening or the prescriptions that would have come with it.
Treatment
There is no medication. The treatment is a strict, lifelong gluten-free diet, and it is effective — the gut lining heals and symptoms resolve for the great majority.
- Strict matters more than it sounds. Traces cause damage, including in people who feel nothing after eating them
- Referral to a dietitian is part of standard care, not an optional extra
- Gluten-free oats can be included at any stage, with a review of how you respond
- Immunisation against pneumococcus is recommended, because coeliac disease can affect spleen function
- Gluten-free staple foods on prescription are available in some areas, though availability varies considerably around the UK
Living gluten-free covers labelling, cross-contamination and eating out.
What happens if it is not treated
- Iron deficiency anaemia, and B12 or folate deficiency
- Osteoporosis, from poor calcium and vitamin D absorption
- Subfertility and pregnancy complications, including low birth weight
- Persistent fatigue and reduced quality of life
- Small bowel lymphoma — rare, and the risk falls with a strict gluten-free diet
The risks are what make this worth diagnosing properly rather than self-managing. They accrue silently, in people who feel reasonably well.
Follow-up and annual review
NICE recommends an annual review, which should include measuring weight and height, reviewing symptoms, and considering whether dietary assessment and specialist dietetic advice are needed.
Blood tests alone do not prove the diet is working. NICE is explicit that serological testing should not be used on its own to determine whether gluten has been excluded. Antibody levels are a useful signal, not a verdict.
If symptoms continue on a gluten-free diet
Persisting symptoms are common enough to have a defined approach, and the order matters:
| Step | What it involves |
|---|---|
| Check the diagnosis is right | Reviewing the original tests, particularly if the diet was started before biopsy |
| Look for hidden gluten | Referral to a specialist dietitian to find ongoing exposure — usually cross-contamination or an overlooked ingredient |
| Look for coexisting conditions | IBS, lactose intolerance, small bowel bacterial overgrowth, microscopic colitis |
| Consider refractory coeliac disease | Rare, and only after gluten exposure and other conditions have been excluded. Managed in a specialist centre |
Repeat biopsy is considered where antibody levels stay persistently raised after 12 months or symptoms persist.
Conditions that overlap
- Irritable bowel syndrome — coeliac serology should be done before settling on an IBS diagnosis in an adult. See IBS red flags
- Bloating — a common presentation, and one where coeliac is a specific thing to exclude rather than assume
- Constipation — coeliac does not always cause diarrhoea; constipation is a recognised presentation
- Type 1 diabetes and autoimmune thyroid disease — both warrant testing at diagnosis, because autoimmune conditions cluster
- Dermatitis herpetiformis — the skin form, treated with the same gluten-free diet
Coeliac UK is the national charity and the most practical source of food lists, prescribing information and support.
Frequently Asked Questions
Can I be tested for coeliac disease if I have already stopped eating gluten?
Not reliably. Both the blood test and the biopsy detect the body's response to gluten, so they normalise once gluten is removed. You would need to go back to eating gluten in more than one meal every day for at least six weeks before testing, which is why NICE advises not starting a gluten-free diet until a specialist has confirmed the diagnosis.
What is the difference between coeliac disease and gluten intolerance?
Coeliac disease is an autoimmune condition in which gluten causes the immune system to damage the small intestine, detectable by antibodies and biopsy, with long-term risks including anaemia, osteoporosis and subfertility. Non-coeliac gluten sensitivity produces no antibodies and no gut damage, has no specific diagnostic test, and carries no known long-term complications.
How is coeliac disease diagnosed?
A blood test for total IgA and IgA tissue transglutaminase is the first step in young people and adults, with endomysial antibodies used if the result is weakly positive. A positive result leads to referral to a gastrointestinal specialist for an endoscopic biopsy of the small intestine, which confirms the diagnosis.
Who should be tested for coeliac disease?
Anyone with persistent unexplained gastrointestinal symptoms, prolonged fatigue, unexpected weight loss, severe or persistent mouth ulcers, or unexplained iron, B12 or folate deficiency. Also everyone with type 1 diabetes or autoimmune thyroid disease at diagnosis, adults being assessed for IBS, and first-degree relatives of someone with coeliac disease.
Does coeliac disease always cause diarrhoea?
No. Many people present instead with the consequences of poor absorption, such as iron deficiency anaemia, fatigue or bone thinning, and some have constipation rather than diarrhoea. A proportion have no symptoms they would have mentioned and are found through screening because a relative has the condition.
Will a gluten-free diet fix it?
For most people, yes. A strict lifelong gluten-free diet allows the gut lining to heal and resolves symptoms, and it reduces the long-term risks. Strictness matters more than it sounds, because traces cause damage even in people who feel nothing after eating them.
References
- National Institute for Health and Care Excellence. Coeliac disease: recognition, assessment and management (NG20). nice.org.uk
- NHS. Coeliac disease. nhs.uk
- NHS. Coeliac disease: diagnosis. nhs.uk
- Coeliac UK. Non-coeliac gluten sensitivity. coeliac.org.uk
- National Institute for Health and Care Excellence. Irritable bowel syndrome in adults: diagnosis and management (CG61). nice.org.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Do not start a gluten-free diet before coeliac testing is complete, as doing so makes the tests unreliable. Always consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.
