Coeliac Disease
An immune-mediated response to dietary gluten that injures the small-bowel mucosa and causes gastrointestinal or extraintestinal disease; confirm it while gluten is being eaten before starting a lifelong gluten-free diet.
Definition
Coeliac disease is an immune-mediated systemic disorder triggered by dietary gluten in genetically susceptible people, causing small-intestinal mucosal injury and associated gastrointestinal or extraintestinal disease that improves with a strict gluten-free diet.
Epidemiology
Coeliac disease affects about 1% of people and is frequently underdiagnosed. Risk is higher in first-degree relatives and in people with type 1 diabetes, autoimmune thyroid disease, Down syndrome or Turner syndrome.
Pathophysiology
Gluten exposure activates an immune response in susceptible small bowel mucosa. Intraepithelial lymphocytosis, crypt hyperplasia and villous injury reduce absorptive surface area and account for malabsorption, iron and vitamin deficiencies, bone disease and the broad extraintestinal phenotype.
First principles
Coeliac disease is an immune-mediated enteropathy, not an allergy or simple intolerance
In genetically susceptible people, gluten triggers an immune response in the small intestine. The resulting intraepithelial lymphocytosis, crypt hyperplasia and villous injury reduce absorptive surface area and can produce both malabsorption and non-gastrointestinal manifestations.1,2
Malabsorption explains why the presentation is wider than diarrhoea
Coeliac disease may present with diarrhoea, abdominal symptoms, weight loss or faltering growth, but also with fatigue, iron-, folate- or B12-deficiency anaemia, metabolic bone disease, mouth ulcers, neurological symptoms or associated autoimmune disease. Case-finding should therefore be driven by the whole syndrome rather than a single bowel symptom.1,3,2
Diagnostic tests measure the response to gluten
Serology and duodenal histology can become less informative after gluten has been removed. Test while the person is eating a gluten-containing diet; if gluten has already been restricted, discuss a supervised gluten challenge and specialist assessment rather than accepting a negative result or labelling the condition from symptoms alone.1,2,4
The treatment removes the trigger but requires structured support
A confirmed diagnosis is managed with a strict lifelong gluten-free diet, specialist dietetic support and monitoring for nutritional, bone, splenic and persistent-disease complications. Symptom improvement alone does not prove coeliac disease and serology alone does not prove mucosal healing or complete dietary exclusion.1,2,5,6
Presentation
Chronic or relapsing gastrointestinal symptoms, malabsorption or an extraintestinal clue such as iron-deficiency anaemia, fatigue, mouth ulcers, metabolic bone disease or dermatitis herpetiformis.1,3,2
Cardinal features
- Persistent diarrhoea, abdominal pain, bloating or flatulence
- Unexpected weight loss or faltering growth
- Unexplained iron-, folate- or vitamin B12-deficiency anaemia
- Prolonged fatigue or severe or persistent mouth ulcers
- Metabolic bone disease, unexplained neurological symptoms or subfertility
- Type 1 diabetes, autoimmune thyroid disease or an affected first-degree relative
- Dermatitis herpetiformis or another extraintestinal presentation
Red flags
- Weight loss, bleeding, dysphagia, persistent vomiting or another alarm feature needing an appropriate urgent pathway
- Severe anaemia, dehydration, electrolyte disturbance or malnutrition
- Persistent symptoms despite a reported strict gluten-free diet
- Persistently high serology or unexplained anaemia after 12 months of treatment
- Suspected refractory disease, severe osteoporosis or a fragility fracture
Investigations
IgA tissue transglutaminase with total IgA
Use IgA-tTG as the first-line serological investigation and check total IgA alongside it. If selective IgA deficiency is present, use IgG-based coeliac serology; use IgA endomysial antibody when IgA-tTG is weakly positive according to the laboratory pathway.
Expected finding: Raised IgA-tTG with normal total IgA, or an appropriate IgG-based positive result when IgA deficient.
1,2,4Confirm adequate gluten exposure before testing
Testing is most reliable while the person is eating gluten. NICE advises gluten in more than one meal every day for at least 6 weeks; the 2026 BSG adult guideline advises 3–6 g daily for at least 6 weeks if gluten has already been restricted. If reintroduction is not tolerated or is unsafe, refer to gastroenterology rather than improvising a diagnosis.
Expected finding: A documented gluten-containing diet during the diagnostic pathway, or specialist interpretation if exposure has been inadequate.
1,2,4Specialist diagnostic pathway and duodenal histology
Refer adults with positive serology, and people with negative serology but persistent clinical suspicion, to gastroenterology. When biopsy is required, the current BSG adult guideline recommends at least four biopsies from the second part of the duodenum and two from the bulb while the patient is consuming gluten.
Expected finding: Characteristic coeliac histology may show increased intraepithelial lymphocytes, crypt hyperplasia and villous atrophy; interpret the result with serology and clinical context.
1,7,2,3Consider the adult no-biopsy pathway only in secondary care
The 2026 BSG guideline allows an optional no-biopsy diagnosis in symptomatic adults assessed in secondary care when IgA-tTG is at least 10 times the assay upper limit of normal, after shared decision-making, local assay validation and exclusion of red flags or another reason for endoscopy. It is not a primary-care shortcut and does not replace paediatric pathways.
Expected finding: A specialist-documented decision for biopsy or the validated adult no-biopsy pathway, with the diagnostic uncertainty and patient preference addressed.
2,4,1Assess nutritional and bone consequences
Check for deficiencies in iron, folate, vitamin B12, vitamin D and calcium at diagnosis and during follow-up, and assess bone health. NICE advises considering DEXA when the annual review raises concern; the 2026 BSG adult guideline advises a DXA scan one year after starting a gluten-free diet for newly diagnosed adults.
Expected finding: Deficiency or low bone density may be present and should prompt replacement, dietetic support and bone-health management according to the relevant national guidance.
1,2,3Management
| Step | Detail | Source |
|---|---|---|
| Recognise coeliac disease and test before changing the diet | Offer coeliac serology for persistent unexplained gastrointestinal symptoms, faltering growth, prolonged fatigue, unexpected weight loss, severe or persistent mouth ulcers, unexplained iron-, B12- or folate-deficiency anaemia, type 1 diabetes, autoimmune thyroid disease, adult IBS and affected first-degree relatives. Also consider testing for metabolic bone disease, unexplained neurological symptoms, subfertility or recurrent miscarriage, unexplained raised liver enzymes, dental enamel defects, Down syndrome or Turner syndrome. Do not start a gluten-free diet before specialist confirmation, even after positive serology.1,3 | NICE NG20 recommendations 1.1.1 to 1.1.6 |
| Keep gluten exposure adequate during diagnostic testing | Explain that serology and biopsy are less reliable after gluten restriction. NICE advises gluten in more than one meal every day for at least 6 weeks; the current BSG adult guideline recommends 3–6 g daily for at least 6 weeks when a gluten challenge is needed. If the person cannot or will not reintroduce gluten, refer to gastroenterology and explain that confirmation may be difficult rather than making a presumptive diagnosis.1,2,4 | NICE NG20 and BSG 2026 adult coeliac guideline |
| Confirm the diagnosis through the appropriate specialist pathway | Use IgA-tTG with total IgA, then IgA EMA for a weakly positive tTG or IgG-based serology in IgA deficiency according to the laboratory pathway. Refer positive results, and persistently suspicious negative results, to gastroenterology. In adults, biopsy remains appropriate unless a secondary-care specialist offers the optional 2026 BSG no-biopsy pathway for symptomatic patients with IgA-tTG at least 10 times the upper limit of normal, no red flags or competing indication for endoscopy, a locally validated assay and shared decision-making.1,2,4,3 | NICE NG20 and BSG 2026 adult coeliac guideline |
| Start a strict lifelong gluten-free diet after confirmation | Once coeliac disease is confirmed, start a strict lifelong gluten-free diet and refer to a specialist dietitian for practical food-label, cross-contamination, eating-out and nutritional advice. Signpost Coeliac UK or an equivalent established disease-advocacy group. Gluten-free oats can be discussed with the patient and introduced with appropriate clinical follow-up; do not imply that symptom improvement alone confirms the diagnosis.1,5,2,4 | NICE NG20, NHS treatment information and BSG 2026 adult coeliac guideline |
| Correct deficiencies and assess bone health | Assess iron, folate, vitamin B12, vitamin D and calcium at diagnosis and follow-up; replace deficiencies according to general national prescribing and nutrition guidance. Assess fracture risk and bone health. For adults, the 2026 BSG guideline advises DXA one year after starting a gluten-free diet, while NICE advises referral for DEXA or active bone treatment when the clinical review identifies concern.1,2,3 | NICE NG20 and BSG 2026 adult coeliac guideline |
| Apply the current national pneumococcal vaccination pathway | Assess whether coeliac disease has caused splenic dysfunction. The current UK Green Book and NHS-facing treatment advice state that coeliac disease without evidence of splenic dysfunction does not usually require additional pneumococcal vaccination after age 2; people with evidence of splenic dysfunction should follow the national asplenia or splenic-dysfunction schedule. The 2026 BSG adult guideline advises pneumococcal vaccination for all adults with coeliac disease. For this exam and UK programme-facing textbook, the current Green Book is the normative vaccine-eligibility source; local specialist advice can address individual risk.8,5,2 | UK Green Book pneumococcal guidance, NHS coeliac treatment information and BSG 2026 adult coeliac guideline |
| Provide structured early and ongoing follow-up | Offer at least annual review under NICE, including weight, height, symptoms, diet and adherence assessment, and dietetic or nutritional support. The 2026 BSG adult guideline recommends regular follow-up for up to 2 years after diagnosis, with patient-initiated follow-up considered for people who respond well thereafter and systematic follow-up for poor adherence, inadequate response or complications. Do not use tTG alone to prove gluten exclusion or mucosal healing; combine symptoms, dietetic assessment and relevant investigations.1,6,2 | NICE NG20, Coeliac UK follow-up guidance and BSG 2026 adult coeliac guideline |
| Escalate persistent or refractory symptoms to specialist care | If symptoms persist despite advice to exclude gluten, first review the original diagnosis, involve a specialist dietitian to identify ongoing gluten exposure and investigate coexisting conditions such as IBS, lactose intolerance, bacterial overgrowth, microscopic colitis or inflammatory colitis. Suspected refractory coeliac disease needs a specialist centre or multidisciplinary pathway; do not label it or start immunosuppression in primary care without specialist assessment.1,5,2 | NICE NG20, NHS treatment information and BSG 2026 adult coeliac guideline |
Illustrations
Differentials
Irritable bowel syndrome
Symptom overlap but no coeliac-specific serology or histology; coeliac testing is recommended in adults with suspected IBS.
Inflammatory bowel disease or microscopic colitis
May cause diarrhoea and weight loss but needs the relevant stool, endoscopic and histological pathway.
Lactose intolerance or other carbohydrate intolerance
Symptoms relate to specific foods and do not explain coeliac serology or duodenal histology.
Pancreatic exocrine insufficiency or small-intestinal bacterial overgrowth
Can cause malabsorption but does not produce the characteristic coeliac serology and biopsy pattern.
Non-coeliac gluten sensitivity
Symptoms attributed to gluten without the diagnostic autoimmune serology or histological evidence of coeliac disease; exclude coeliac disease before dietary labelling.
Complications
- Iron, folate or vitamin B12 deficiency anaemia
- Osteopenia, osteoporosis or fragility fracture
- Functional hyposplenism and increased infection risk
- Dermatitis herpetiformis and other extraintestinal disease
- Persistent or refractory coeliac disease
- Rare enteropathy-associated T-cell lymphoma or small-bowel adenocarcinoma
Prognosis
A strict lifelong gluten-free diet improves symptoms and reduces gluten-related complications, but nutritional, bone, splenic and persistent-disease risks require structured follow-up. Persistent symptoms should trigger a diagnostic and dietary review rather than an immediate label of refractory disease.
Guidelines
- Coeliac disease: recognition, assessment and management (NG20) (NICE, 2015)
- Guidelines on the diagnosis and management of adult coeliac disease (British Society of Gastroenterology, 2026)
- Pneumococcal vaccination for older adults and individuals in a clinical risk group (UK Health Security Agency, 2026)
References
- NICE NG20, Coeliac disease: recognition, assessment and management — recommendationsUpdated 2 Sept 2015
- British Society of Gastroenterology, 2026 guidelines on diagnosis and management of adult coeliac diseaseUpdated 20 Apr 2026
- NHS, coeliac disease — diagnosisUpdated 31 Mar 2023
- Coeliac UK, BSG guideline on diagnosis and management of adult coeliac disease — highlights
- NHS, coeliac disease — treatmentUpdated 31 Mar 2023
- Coeliac UK, follow up after diagnosis
- NICE QS134, Coeliac disease — quality statement 3: endoscopic intestinal biopsyUpdated 1 Nov 2022
- UK Health Security Agency, pneumococcal vaccination for older adults and clinical risk groupsUpdated 13 Apr 2026
Evidence checked: 2026-08-03
This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.