Gluten Intolerance Test: How Coeliac Disease, Sensitivity and Wheat Allergy Are Diagnosed

01Types

Three different conditions

• Coeliac disease: an autoimmune reaction to gluten that damages the lining of the small intestine; affects about 1 in 100 people.
• Wheat allergy: an immune (allergic) reaction to wheat proteins, more common in children.
• Non-coeliac gluten or wheat sensitivity: digestive or other symptoms after eating gluten or wheat, without coeliac disease or allergy; the mechanism is not fully understood and FODMAPs may play a role.
• Irritable bowel syndrome can also cause symptoms after wheat-based foods.

02Symptoms

Symptoms that may lead to testing

• Diarrhoea, bloating, abdominal pain or wind.
• Constipation in some people.
• Tiredness, iron-deficiency anaemia or vitamin deficiencies.
• Unexplained weight loss or poor growth in children.
• Mouth ulcers, an itchy blistering rash (dermatitis herpetiformis) or tingling in the hands and feet.
• Fertility problems or osteoporosis at a young age.
• Many people with coeliac disease have mild or no symptoms.

03Coeliac

Testing for coeliac disease

The first test is a blood test for IgA antibodies against tissue transglutaminase (tTG-IgA), with a total IgA level to make sure the result is valid. Some people need additional antibody tests. If the blood test is positive, adults are usually referred for an endoscopy to take small biopsies from the duodenum to confirm the diagnosis; in some children with very high antibody levels, biopsy may be avoided. Clinical guidelines such as NICE recommend eating gluten in more than one meal every day for at least six weeks before testing. People with a close relative with coeliac disease, type 1 diabetes, autoimmune thyroid disease, unexplained anaemia or irritable bowel syndrome symptoms are often offered testing.

04Gluten

Why you must keep eating gluten

Coeliac antibodies and gut damage depend on gluten exposure. If you cut out gluten before testing, antibody levels can fall and the gut lining can heal, giving a false negative result. If you have already gone gluten-free, a doctor may suggest a “gluten challenge”: reintroducing gluten for several weeks before testing. This can be uncomfortable, so it should be planned with a doctor. Our guides to a gluten-free meal plan and a list of gluten-free foods are for after diagnosis.

05Allergy

Testing for wheat allergy

Wheat allergy usually causes symptoms within minutes to two hours of eating wheat, such as hives, itching, swelling, vomiting, wheezing or, rarely, anaphylaxis. Some people react only when they exercise after eating wheat. Diagnosis combines the history with skin prick tests or blood tests for wheat-specific IgE, and sometimes a supervised food challenge. Children often outgrow wheat allergy.

06Sensitivity

Diagnosing non-coeliac gluten sensitivity

There is no blood or breath test for non-coeliac gluten sensitivity. Experts meeting in Salerno proposed a structured approach: first exclude coeliac disease and wheat allergy while still eating gluten, then follow a gluten-free diet for at least six weeks, followed by a blinded reintroduction of gluten to confirm that symptoms return. In practice, many people improve on a low-FODMAP diet, suggesting that fermentable carbohydrates in wheat, rather than gluten itself, are responsible. A dietitian can help work this out; see our guide to the low FODMAP diet.

07Home

Home and online tests

• Home finger-prick coeliac tests detect antibodies, but positive or negative results should be confirmed by a doctor.
• IgG “food intolerance” tests are not recommended; IgG antibodies to foods are normal and do not diagnose intolerance.
• Hair, kinesiology and bioresonance tests have no scientific basis.
• Genetic tests (HLA-DQ2/DQ8) can help rule out coeliac disease if negative, but a positive result is common and does not confirm it.

08Next

What happens after diagnosis

Coeliac disease requires a strict, lifelong gluten-free diet, follow-up blood tests, and checks for nutritional deficiencies and bone health. A dietitian is essential to learn about hidden gluten and cross-contamination. Wheat allergy requires avoidance of wheat, and possibly an emergency plan with adrenaline if reactions are severe. Non-coeliac gluten sensitivity is managed by reducing gluten or wheat to a level that controls symptoms, which may not need to be as strict.

09Cases

Three common situations

• Bloating and tiredness, already gluten-free: talk to a doctor about a planned gluten challenge before testing.
• Sibling diagnosed with coeliac disease: close relatives should be offered a blood test.
• Hives after eating pasta: possible wheat allergy; see a doctor for allergy testing.

10Summary

Key points to remember

• Coeliac disease, wheat allergy and gluten sensitivity are different conditions.
• Coeliac testing needs gluten in the diet for at least six weeks beforehand.
• Non-coeliac gluten sensitivity is diagnosed by excluding other conditions.
• IgG intolerance tests are not reliable.