Symptoms of Coeliac Disease

Coeliac disease is a great imitator. It can present with almost anything:

Classic GI Symptoms	Non-Classic Presentations
Diarrhoea or loose stools	Iron deficiency anaemia (unexplained)
Bloating and wind	Fatigue and low energy
Abdominal pain	Osteoporosis / fractures
Steatorrhoea (fatty, pale stools)	Infertility or recurrent miscarriage
Weight loss / failure to thrive	Neurological symptoms (gluten ataxia)
Mouth ulcers	Raised liver enzymes (unexplained)
	Dermatitis herpetiformis (blistering rash)

Do Not Go Gluten-Free Before You Are Tested

This is the single most consequential thing on this page. Both the blood tests and the biopsy for coeliac disease work by detecting your immune reaction to gluten. Remove gluten and the reaction fades, the antibodies fall, and the lining of the small intestine begins to heal. The tests then come back normal — not because you do not have coeliac disease, but because you have already partly treated it.

A review of this problem puts it plainly: ruling coeliac disease out properly before restricting gluten is essential, precisely because doing it the other way round creates diagnostic uncertainty that is difficult to resolve afterwards.²

The common sequence that causes troubleSomeone feels unwell, tries cutting out gluten, feels better, and only then asks to be tested. By that point the tests may be uninformative, and the only route to a clear answer is to start eating gluten again for a period — which is unpleasant when it is exactly what was making you ill.

If you are already gluten-free and want a diagnosis, that is a gluten challenge, and it needs to be planned with a clinician rather than improvised. The evidence does not yet support one standard protocol for how much gluten, or for how long, so the decision is made case by case.²

Why a Firm Diagnosis Is Worth Having

If a gluten-free diet already makes you feel better, it is reasonable to ask why the label matters. There are several reasons it does.

Coeliac disease is an autoimmune condition rather than an intolerance, and it carries consequences beyond symptoms: absorption of iron, B12, folate, calcium and vitamin D can be affected, and bone density can suffer — none of which announce themselves. A confirmed diagnosis brings structured follow-up for those things. It also has implications for your relatives, who have a materially higher chance of being affected and can be screened. And it changes how strict the diet needs to be: coeliac disease requires lifelong, complete avoidance, where self-diagnosed sensitivity often does not.

There is also the possibility that gluten is not the culprit. Feeling better on a gluten-free diet does not by itself confirm coeliac disease, and testing distinguishes it from other conditions that improve on the same diet for different reasons. That distinction is worth having before committing to a lifelong restriction.

Blood Tests for Coeliac Disease

Test	Sensitivity	Notes
tTG-IgA (tissue transglutaminase)	95–98%	Primary screening test: must be done while EATING gluten
Total IgA level	:	Must check IgA deficiency (3% of coeliacs): gives false negative tTG
EMA (endomysial antibody)	95–99%	More specific but expensive: confirms positive tTG
DGP (deamidated gliadin peptide) IgG	:	Used when IgA deficient
FBC	:	Anaemia (iron, B12, folate deficiency from malabsorption
Iron, ferritin, B12, folate	:	Malabsorption profile
Liver enzymes	:	Mildly elevated in 50% of untreated coeliacs

Gluten Must Be EatenBlood tests and biopsy are only accurate if you are eating gluten regularly (at least 4 slices of bread equivalent per day for 6 weeks). Going gluten-free before testing will give a FALSE NEGATIVE result.

Diagnosis: The Endoscopy Biopsy

Positive blood tests must be confirmed with upper GI endoscopy. Biopsies are taken from the duodenum and show villous atrophy (flattening of the gut lining): the hallmark of coeliac disease.

Marsh Classification	Biopsy Appearance	Clinical Significance
Marsh 0	Normal	No coeliac
Marsh 1	Increased intraepithelial lymphocytes	Possible coeliac
Marsh 2	Crypt hyperplasia	Coeliac likely
Marsh 3a/b/c	Partial/subtotal/total villous atrophy	Definite coeliac disease

Non-Coeliac Gluten SensitivitySome people without coeliac disease feel better on a gluten-free diet. NCGS is a real condition but lacks the villous atrophy and autoimmune features of coeliac. It doesn't have the same long-term complications.

Can coeliac disease develop in adulthood?

Yes. Coeliac 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.

Is a gluten-free diet expensive?

Gluten-free specialty products are expensive, but a naturally gluten-free diet (rice, potatoes, corn, fresh meat, fish, vegetables, legumes) is not. Focus on whole foods rather than processed GF alternatives.

What is dermatitis herpetiformis?

A specific blistering skin rash caused by gluten: it occurs outside the gut and is pathognomonic of coeliac disease. It responds to a strict gluten-free diet.

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.

Celiac Disease. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK441900
Gluten-Associated Medical Problems. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK538505
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

Coeliac Disease: Symptoms, Testing & Gluten-Free Life