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Coeliac Disease: Symptoms, Testing & Gluten-Free Life

Coeliac disease affects 1% of the population: but 80% are undiagnosed. It's not an allergy but an autoimmune condition where gluten destroys the gut lining. The only treatment is strict lifelong gluten avoidance.1

Written by Suman Konda, Clinical Pharmacist · Based on peer-reviewed sources · Editorial policy · Not medical advice

Last reviewed and updated: · How we check our content

Prevalence
1% of population (80% undiagnosed)
Test
tTG-IgA blood test
Diagnosis confirmed by
Duodenal biopsy (endoscopy)
Treatment
Strict gluten-free diet for life

Quick answer

Coeliac disease affects about 1% of the population, but roughly 80% are undiagnosed. It is an autoimmune condition, not an allergy: gluten destroys the small-intestine lining. The one rule that matters most: never start a gluten-free diet before testing.

What coeliac disease is

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Coeliac disease is an autoimmune condition in which gluten — a protein in wheat, barley and rye — triggers an immune attack that destroys the lining of the small intestine. It is not a food allergy and not a simple intolerance: the damage impairs absorption of iron, B12, folate, calcium and vitamin D, and can reduce bone density over time.1

It affects about 1% of the population, but roughly 80% of cases are undiagnosed, partly because it is a great imitator: it can present with diarrhoea and bloating, or with none of the classic gut symptoms at all — unexplained anaemia, fatigue, infertility, neurological symptoms or a blistering skin rash (dermatitis herpetiformis). It can also develop at any age, including the 40s, 50s and beyond.

The only treatment is a strict, lifelong gluten-free diet. That is why a firm diagnosis matters: it changes how strict the diet must be, brings structured follow-up, and allows relatives — who carry a materially higher risk — to be screened.

How coeliac disease is usually evaluated

Evaluation has two stages — blood tests first, then biopsy to confirm — and both only work while you are eating gluten:

TestRoleNotes
tTG-IgA (tissue transglutaminase)Primary screening testSensitivity 91–98%; must be done while eating gluten
Total IgA levelValidity checkIgA deficiency (about 3% of coeliacs) causes false-negative tTG
EMA (endomysial antibody)Confirms positive tTGMore specific but more expensive
DGP-IgG (deamidated gliadin peptide)AlternativeUsed when IgA deficient
FBC; iron, ferritin, B12, folateMalabsorption profileAnaemia and nutrient deficiencies are common at diagnosis
Liver enzymesAssociated findingMildly elevated in about 50% of untreated coeliacs

Positive blood tests are confirmed with upper GI endoscopy and duodenal biopsy, which shows villous atrophy graded by the Marsh classification (Marsh 3a/b/c = definite coeliac disease). Non-coeliac gluten sensitivity is real but lacks the villous atrophy and autoimmune features, and does not carry the same long-term complications.4

Your next steps if coeliac disease is suspected

The order of operations matters more here than in almost any other work-up:

  1. Keep eating gluten until tested. This is the single most consequential step. Removing gluten normalises the blood tests and biopsy, creating diagnostic uncertainty that is difficult to resolve afterwards. Tests need regular gluten intake — roughly 4 slices of bread equivalent daily for 6 weeks.2
  2. Get tTG-IgA plus total IgA. The screening blood test, done while eating gluten. If you already went gluten-free, discuss a supervised gluten challenge with your doctor rather than guessing.
  3. If positive, proceed to endoscopy. Duodenal biopsy confirms the diagnosis and grades the damage; it is what separates coeliac disease from gluten sensitivity.
  4. If confirmed, get structured follow-up. Ask about a dietitian referral, screening of first-degree relatives, and checks of iron, B12, folate, calcium, vitamin D and bone density.
  5. Commit to lifelong strict avoidance only with a diagnosis. Coeliac disease requires complete avoidance; self-diagnosed sensitivity often does not — another reason the label matters.

The coeliac testing sequence

Coeliac testing follows a fixed order: screen with blood tests first, confirm with biopsy. Each step has a defined role:

StepTestWhat it clarifies
1. First-line screentTG-IgA plus total IgAtTG-IgA is the most sensitive screen; total IgA is measured alongside because IgA deficiency causes false negatives
2. Confirmatory antibodyEMA (endomysial antibody)Highly specific; supports the diagnosis when positive
3. Definitive diagnosisUpper GI endoscopy with duodenal biopsyShows villous atrophy; remains the gold standard
Rule-out onlyHLA-DQ2 / HLA-DQ8A negative result makes coeliac disease very unlikely; a positive result alone does not diagnose it

All testing should be done while still eating gluten: starting a gluten-free diet beforehand can normalise both antibodies and biopsy.

These are approximate bands, not quotes: prices vary by city and lab. Where possible, choose a NABL-accredited lab, and confirm the biopsy includes Marsh grading in the report.

Practical notes

A food-and-symptom diary is genuinely useful while coeliac disease is being evaluated. Note what you ate, when symptoms appear, and how severe they are — patterns like symptoms consistently following wheat-based meals help your doctor, though only proper testing can confirm the diagnosis.

The single most important thing to know: do not cut out gluten before testing. Antibody tests and biopsies depend on you still eating gluten, and going gluten-free early can produce a false negative that delays diagnosis by months. If you have already reduced gluten, tell your doctor — they may ask you to reintroduce it for some weeks before testing.

If the diagnosis is confirmed, the gluten-free diet is the treatment, and most people are referred to a dietitian to learn it properly. It is stricter than it sounds: label reading, avoiding cross-contamination in shared kitchens, and checking medicines and supplements become routine. Discuss the referral with your doctor rather than improvising.

Follow-up usually includes repeating the tTG-IgA antibody test at intervals after going gluten-free — falling levels suggest the diet is working. Your doctor may also check for nutrient deficiencies that built up before diagnosis and discuss bone health monitoring. Ask what schedule of reviews suits you.

In India

In India, the tTG-IgA antibody test typically costs around ₹1,200–₹2,500 at private labs, though prices vary by city and lab. Fuller coeliac panels that add related antibodies can cost more, and an upper GI endoscopy with biopsy, if advised, is a separate hospital charge — ask for a written estimate beforehand.

Choose a NABL-accredited lab for antibody testing, since assay quality affects reliability, and home sample collection is available in major cities. The reference range printed on your own report is the one that counts — cut-offs differ between test kits.

Frequently asked questions

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What are the symptoms of coeliac disease?

Coeliac disease is a great imitator and can present with almost anything. Classic gut symptoms include diarrhoea or loose stools, bloating and wind, abdominal pain, steatorrhoea (fatty, pale stools), weight loss and mouth ulcers. Non-classic presentations are common: unexplained iron deficiency anaemia, fatigue, osteoporosis or fractures, infertility or recurrent miscarriage, neurological symptoms such as gluten ataxia, raised liver enzymes and the blistering rash dermatitis herpetiformis.

Should I go gluten-free before being tested for coeliac disease?

No — this is the single most consequential thing to know. Both the blood tests and the biopsy detect your immune reaction to gluten. Remove gluten and the reaction fades: antibodies fall, the small-intestine lining begins to heal, and the tests come back normal — not because you do not have coeliac disease, but because you have already partly treated it. Testing must be done while eating gluten regularly (at least 4 slices of bread equivalent per day for 6 weeks), or the result can be a false negative.

Why is a firm diagnosis of coeliac disease worth having?

A confirmed diagnosis brings structured follow-up for things that do not announce themselves: absorption of iron, B12, folate, calcium and vitamin D can be affected and bone density can suffer. It has implications for relatives, who have a materially higher chance of being affected and can be screened. And it changes how strict the diet must be: coeliac disease requires lifelong, complete avoidance. Feeling better on a gluten-free diet does not by itself confirm coeliac disease.

How is coeliac disease confirmed?

Positive blood tests are confirmed with upper GI endoscopy: biopsies taken from the duodenum show villous atrophy (flattening of the gut lining), the hallmark of coeliac disease. The Marsh classification grades the biopsy from Marsh 0 (normal) through Marsh 1–2 (possible/likely) to Marsh 3a/b/c (partial, subtotal or total villous atrophy — definite coeliac disease).

Can coeliac disease develop in adulthood?

Yes. Coeliac disease can develop at any age — many people are diagnosed in their 40s, 50s and beyond. An infection, surgery, pregnancy or major stress can trigger its onset in genetically susceptible individuals.

My test was negative but I feel much better avoiding gluten — what should I do?
Keep following up with your doctor rather than settling the question yourself. Feeling better off gluten does not confirm coeliac disease, and other conditions can behave similarly. Your doctor may suggest further evaluation or a supervised approach — do not abandon the diagnostic process based on symptoms alone.
Should my children or siblings be tested?
Coeliac disease runs in families, so first-degree relatives carry a higher risk and screening is often recommended for them. Discuss with your doctor who in the family should be tested and when — it is a simple blood test, and catching it early avoids years of unexplained symptoms.
How strict do I need to be about cross-contamination when eating out?
Cross-contamination is one of the commonest reasons symptoms persist on a gluten-free diet — shared fryers, tongs and cooking surfaces all matter. When eating out, ask direct questions about how food is prepared. A dietitian can teach you what to ask; discuss a referral with your doctor.
Are oats allowed on a gluten-free diet?
Pure, uncontaminated oats are tolerated by most people with coeliac disease, but commercial oats are often contaminated with wheat during processing, and a minority react to oats themselves. Look for certified gluten-free labelling and discuss it with your doctor or dietitian before making oats a staple.

References

The clinical information on this page is drawn from peer-reviewed sources indexed by the US National Library of Medicine. Links go to the source so you can read it yourself.

  1. Celiac Disease. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK441900
  2. Gluten-Associated Medical Problems. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK538505
  3. Popp A, Laurikka P, Czika D, Kurppa K. The role of gluten challenge in the diagnosis of celiac disease: a review. Expert Rev Gastroenterol Hepatol. 2023;17(7):691–700. PMID 37243608 · doi:10.1080/17474124.2023.2219893
  4. Sheppard AL, Elwenspoek MMC, Scott LJ, et al. Systematic review with meta-analysis: the accuracy of serological tests to support the diagnosis of coeliac disease. Aliment Pharmacol Ther. 2022;55(5):514–527. PMID 35043426 · doi:10.1111/apt.16729
Medical Disclaimer: This page is for general education only and does not replace professional medical advice. Always consult a qualified healthcare provider.
Written and medically reviewed by Suman Konda, Clinical Pharmacist · Sources linked to PubMed · Not medical advice: see our disclaimer