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Coeliac Disease & Gluten Intolerance

An awareness guide to coeliac disease, non-coeliac gluten sensitivity and wheat allergy — and the role of IgA/IgG antibody blood testing

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⚠️ Before you test: please keep eating gluten

Coeliac antibody blood tests only work reliably while gluten is still in your diet. NICE guideline NG20 recommends eating gluten in more than one meal per day for at least six weeks before testing. If you have already cut back, your immune response — and therefore your antibody levels — may have dropped, which can produce a falsely negative result.

If you have a strong personal or family history suggesting coeliac disease and have already gone gluten-free, please speak to your GP before booking. The right pathway may be a medically supervised gluten challenge rather than immediate antibody testing. For up-to-date guidance, see Coeliac UK and NICE NG20.

What Is Coeliac Disease?

Coeliac disease is a lifelong autoimmune condition in which eating gluten — a family of proteins found in wheat, barley and rye — triggers the immune system to attack the lining of the small intestine. Over time this damages the villi, the small finger-like projections that absorb nutrients, which can lead to a wide range of symptoms and longer-term complications including iron-deficiency anaemia, osteoporosis and impaired growth in children.

According to Coeliac UK, around 1 in 100 people in the UK has coeliac disease, but it is estimated that only around 36% have been clinically diagnosed. First-degree relatives of someone with coeliac disease are at higher risk (around 1 in 10), as are people with Type 1 diabetes, autoimmune thyroid disease, Down's syndrome and Turner syndrome.

Coeliac disease is a clinical diagnosis made by a doctor — usually a GP working with a gastroenterologist — typically combining serology (antibody blood tests), symptom assessment and, in adults, an endoscopic small-bowel biopsy. Blood-based testing has a defined, supportive role in that pathway; it is the recommended first-line screen and is what private services such as ours can help with.

Common Symptoms

Coeliac disease can present very differently from person to person. Some people have obvious digestive symptoms; others have predominantly "extra-intestinal" features and no significant bowel complaints at all.

Digestive features

· Persistent diarrhoea or constipation
· Bloating and abdominal discomfort
· Excessive wind
· Nausea and vomiting
· Unintentional weight loss

Extra-intestinal features

· Persistent fatigue
· Iron-, folate- or B12-deficiency anaemia
· Mouth ulcers
· Dermatitis herpetiformis (itchy, blistering rash)
· Reduced bone density / unexplained fractures
· Subfertility or recurrent miscarriage
· Neurological features (e.g. ataxia, peripheral neuropathy)

Coeliac Disease vs Wheat Allergy vs NCGS

These three conditions are commonly confused because they can share digestive symptoms and all involve cereals. The mechanisms, tests and management are entirely different.

Feature	Coeliac Disease	Wheat Allergy	NCGS
Mechanism	Autoimmune	IgE allergic	Non-immune (unclear)
Trigger	Gluten (wheat, barley, rye)	Wheat proteins	Gluten / FODMAPs / ATIs
Onset	Gradual	Minutes to 2 hours	Hours to days
Anaphylaxis risk	No	Yes (esp. WDEIA)	No
Diagnostic blood test	tTG-IgA, EMA, DGP	Specific IgE (e.g. ω-5-gliadin)	None validated
Bowel damage on biopsy	Yes (villous atrophy)	No	No

The Antibody Tests Used in Coeliac Screening

NICE guideline NG20 recommends a stepped serological approach, normally led by your GP. The same antibody markers are what private screening services use.

tTG-IgA (tissue transglutaminase IgA)

The recommended first-line test. It has high sensitivity and specificity for coeliac disease in people who are eating gluten regularly. Total IgA is usually measured alongside it, because around 2–3% of people with coeliac disease have selective IgA deficiency, which would otherwise produce a false-negative tTG-IgA result.

DGP-IgG (deamidated gliadin peptide IgG)

Used as a second-line test in adults with IgA deficiency, and in some paediatric pathways. It looks for IgG-class antibodies and so is not affected by IgA status.

EMA-IgA (endomysial antibodies)

Used to confirm a positive tTG-IgA result. EMA has very high specificity, which makes it a useful confirmatory test ahead of specialist referral.

Our gluten sensitivity profile covers the coeliac-associated antibody markers used in this pathway — the full panel and reference ranges are listed on the test page.

HLA-DQ2 / DQ8 Genetic Typing

Almost everyone with coeliac disease carries one of two genetic markers: HLA-DQ2 (most commonly) or HLA-DQ8. The main clinical value of HLA typing lies in its negative predictive value: if you test negative for both, coeliac disease becomes extremely unlikely (less than 1%).

However, a positive HLA result is far less informative on its own. Around 30–40% of the general UK population carries DQ2 or DQ8 without ever developing coeliac disease. HLA typing therefore helps to rule out coeliac disease but does not rule it in.

HLA typing is most often requested by gastroenterology specialists, particularly when antibody results are equivocal, when someone is already on a gluten-free diet and a gluten challenge is impractical, or when screening close relatives of a person with confirmed coeliac disease.

Non-Coeliac Gluten Sensitivity (NCGS)

Some people experience digestive or extra-intestinal symptoms that improve on a gluten-free diet but who do not have coeliac disease or wheat allergy on testing. This pattern is described as non-coeliac gluten sensitivity (NCGS), sometimes called non-coeliac wheat sensitivity.

NCGS is currently a diagnosis of exclusion: there are no validated blood biomarkers and no characteristic biopsy findings. It is recognised in clinical guidance but its mechanisms remain unclear — fermentable carbohydrates (FODMAPs) and wheat amylase trypsin inhibitors (ATIs) have both been proposed.

Because there is no diagnostic test for NCGS, the safest order of investigation is to rule out coeliac disease and wheat allergy first — while still eating gluten — before any dietary trial. This avoids missing a more serious autoimmune diagnosis.

How Testing Works

Choose Your Test

Select from our range of allergy blood tests and book a convenient time at our South Kensington clinic. No GP referral needed.

Nurse Blood Draw

A qualified nurse takes a small blood sample at our clinic. The appointment is quick and straightforward.

Get Your Results

Results are sent directly to you, typically within a few working days. Share them with your GP or specialist to guide your next steps.

Coeliac & Gluten Sensitivity Profile

Comparing the two panels? See the Gluten & Coeliac Blood Test category hub → for the full IgE vs IgA/IgG comparison and side-by-side test breakdown.

A nurse-collected venous blood sample analysed for the coeliac-associated antibody markers used in screening pathways. Designed to support investigation with your GP or gastroenterologist — not to provide a stand-alone diagnosis. Results are released to you in a clearly formatted laboratory report.

View the Gluten Sensitivity Profile →

Pair with, where relevant:

Tests Relevant to Gluten-Related Conditions

Our Role in the Diagnostic Pathway

AllergyClinic.co.uk is a CQC-registered, nurse-led diagnostic service. All blood samples are taken by registered nurses experienced in allergy and intolerance pathways, processed by an accredited laboratory, and returned to you as a clearly formatted report. We do not diagnose coeliac disease, interpret your results into a clinical decision, prescribe a gluten-free diet, or arrange biopsies — those steps sit with your GP and, where indicated, a gastroenterologist.

The safest pathway for someone with persistent symptoms suggestive of coeliac disease is: GP review → first-line antibody testing → specialist gastroenterology referral if positive or strongly suspected → small-bowel biopsy where indicated. Private blood testing through our clinic can be a useful intermediate step to bring well-organised results to your GP appointment.

Why Choose a Diagnostic-Only Clinic?

Unlike clinics that provide both testing and treatment, our nurse-led service focuses solely on accurate diagnostic testing. Because we don't offer treatments or prescriptions, there is no commercial incentive to recommend unnecessary tests — just honest, impartial results you can trust.

Nurse-Led & Impartial

Our qualified nurses collect your sample — we don't prescribe, treat, or have any reason to upsell.

Results You Own

Your results are sent directly to you. Take them to your GP or a specialist to discuss what's best for your situation.

You Stay in Control

Understand your allergy profile, then decide with your healthcare professional what steps to take next.

Related Conditions

Frequently Asked Questions

What is coeliac disease?

Coeliac disease is a lifelong autoimmune condition in which eating gluten — a protein found in wheat, barley and rye — triggers the immune system to attack the lining of the small intestine. Over time this damages the villi (finger-like projections) that absorb nutrients, which can lead to symptoms such as bloating, diarrhoea, fatigue, iron-deficiency anaemia and weight loss. According to Coeliac UK, around 1 in 100 people in the UK have the condition, but many remain undiagnosed.

What is the difference between coeliac disease and gluten sensitivity?

Coeliac disease is an autoimmune condition with specific antibody markers and characteristic damage to the small bowel visible on biopsy. Non-coeliac gluten sensitivity (NCGS) describes symptoms that improve on a gluten-free diet but where coeliac disease and wheat allergy have been excluded — there are no validated diagnostic biomarkers, so NCGS is considered a diagnosis of exclusion. Wheat allergy is a third, separate, IgE-mediated allergic reaction to wheat proteins.

Do I need to keep eating gluten before a coeliac blood test?

Yes — this is essential. Coeliac antibody tests (such as tTG-IgA) only work reliably while you are eating gluten regularly. NICE guidance (NG20) recommends consuming gluten in more than one meal per day for at least six weeks before testing. Stopping or reducing gluten beforehand can produce a falsely negative result. If you have already started a gluten-free diet, please discuss timing with your GP before booking.

What does the gluten sensitivity profile blood test include?

Our gluten sensitivity profile measures coeliac-associated antibody markers commonly used in the screening pathway. The exact panel and reference ranges are detailed on the test page. The profile is intended to support clinical investigation by your GP or gastroenterologist — it does not on its own diagnose coeliac disease, which requires specialist review and usually an endoscopic small-bowel biopsy.

Is HLA-DQ2 / DQ8 genetic typing useful?

HLA-DQ2 and HLA-DQ8 are the genetic markers associated with coeliac disease. Their main clinical value is in their negative predictive value: if you are negative for both, coeliac disease is extremely unlikely. However, around 30 to 40% of the general UK population carries one of these genes without ever developing coeliac disease, so a positive result alone does not confirm the condition. HLA typing is usually requested through specialist gastroenterology pathways.

Can I be tested if I already follow a gluten-free diet?

Antibody-based testing (such as tTG-IgA) is unreliable once gluten has been removed from the diet, because the immune response that produces these antibodies subsides. Options in this situation include a medically supervised gluten challenge before testing, or genetic HLA-DQ2 / DQ8 typing to help rule the condition out. Please discuss the most appropriate route with your GP before booking — restarting gluten without medical advice is not recommended.

Investigate Coeliac & Gluten Markers

A nurse-led blood test in South Kensington — supporting investigation with your GP, not replacing it. Please continue to eat gluten until your sample is taken.