"You're just a bit sensitive to bread." "Everyone gets bloated." "It's probably stress."
If you've heard one of these, you're in good company. Coeliac disease affects roughly 1 in 100 people in Europe, and most of them have no idea they have it. Many live with tiredness, low iron, or a restless gut for years, and some feel nothing at all. Coeliac screening is a blood test that answers a precise question: is your immune system making the antibodies typical of coeliac disease?
The answer matters. Coeliac disease is very manageable once you know about it. The challenge is knowing.
What coeliac disease is (and what it isn't)
Coeliac disease is an autoimmune condition. When someone with coeliac disease eats gluten, a protein found in wheat, barley, and rye, their immune system mistakes it for a threat and attacks the lining of the small intestine.
That lining is covered in villi, tiny finger-like folds that absorb nutrients from food. Over time, the immune response flattens them. A flattened gut absorbs less iron, folate, vitamin D, and calcium, even when your diet is excellent.
It helps to separate three conditions that often get grouped together under "gluten intolerance":
| Condition | What happens | How it's detected |
|---|---|---|
| Coeliac disease | Autoimmune reaction to gluten that damages the small intestine | Blood test (tTG-IgA), confirmed by a specialist, often with a biopsy |
| Wheat allergy | Classic allergic reaction to wheat proteins, sometimes immediate | Allergy testing (skin prick or specific IgE) |
| Non-coeliac gluten sensitivity | Symptoms after eating gluten, without autoimmune damage or allergy | Diagnosis of exclusion, once coeliac disease and wheat allergy are ruled out |
Only coeliac disease causes lasting intestinal damage, and it leaves a specific antibody pattern in the blood that a screening test can pick up. That's what makes coeliac screening so useful.
Why so many people go undiagnosed
Here's the tricky part: coeliac disease rarely looks the way people expect.
The textbook picture is someone with chronic diarrhoea and weight loss. In reality, the Swiss Federal Nutrition Commission notes that most people with coeliac disease have few symptoms, a single symptom, or none at all ( BAG/EEK, 2010 ). The Swiss patient association IG Zöliakie lists fatigue, anaemia, vitamin deficiencies, bloating, constipation, and bone pain among the common adult symptoms ( IG Zöliakie ). Each of these has a dozen more common explanations.
The coeliac iceberg
Researchers often describe coeliac disease as an iceberg. The diagnosed cases sit above the waterline. Below it is a much larger group who have the condition and don't know.
A large European screening project tested blood samples from several countries and found an overall prevalence of about 1%, with wide variation: 2.4% of adults aged 30 to 64 in Finland, compared with 0.3% in Germany ( Mustalahti et al., 2010 ). A global meta-analysis of 96 studies found antibodies in 1.4% of people and biopsy-confirmed disease in 0.7% ( Singh et al., 2018 ).
The UK charity Coeliac UK estimates that nearly two thirds of people with coeliac disease are still undiagnosed, and that adults wait an average of 13 years from first symptoms to diagnosis ( Coeliac UK ). There is no equivalent Swiss figure, but there is little reason to expect Switzerland to be very different.
Why the delay is so long
Three things tend to slow diagnosis:
- Symptoms overlap with common conditions. Bloating and irregular bowel habits often get labelled as irritable bowel syndrome (IBS). Coeliac UK reports that people first diagnosed with IBS wait a median of 7.1 years for their coeliac diagnosis ( Coeliac UK ).
- Symptoms appear outside the gut. Low iron, low bone density, mouth ulcers, or an itchy blistering rash called dermatitis herpetiformis can all be the first sign.
- Self-treatment muddies the picture. Many people cut back on gluten because they feel better without it. That's understandable, and it can make later testing unreliable (more on that below).
How coeliac screening works
Coeliac screening is a blood test. At Ahead Health, it measures two markers ( see our biomarkers ).
Marker 1: Anti-tissue transglutaminase IgA (tTG-IgA)
Tissue transglutaminase is an enzyme in your gut lining. In coeliac disease, the immune system produces antibodies against it. Measuring these antibodies, called tTG-IgA, is the recommended first-line test for coeliac disease in European and British guidelines, with a pooled sensitivity of around 90% ( Penny et al., 2026 ).
Marker 2: Total immunoglobulin A (IgA)
This one is easy to overlook, and it's essential. tTG-IgA is an IgA antibody. Some people naturally produce very little IgA, a condition called selective IgA deficiency. It affects roughly 1 in 500 to 700 people, and about 2% of people with coeliac disease ( Penny et al., 2026 ).
If your total IgA is low, a tTG-IgA result can look normal even when coeliac disease is present. Measuring total IgA alongside tTG-IgA makes sure a negative result means what it says. Both British and European guidelines recommend testing them together, and at Ahead Health we include both in our coeliac screen.
What your results mean
| Result | What it usually means | Next step |
|---|---|---|
| tTG-IgA normal, total IgA normal | Coeliac disease is unlikely at the time of testing, if you were eating gluten regularly. It doesn't rule out gluten sensitivity or wheat allergy. | If symptoms continue or risk factors change, talk to your GP |
| tTG-IgA raised, total IgA normal | Coeliac disease is possible, and more likely the higher the level | Referral to a gastroenterologist to confirm the diagnosis. Keep eating gluten as usual until then. |
| Total IgA low | tTG-IgA may be falsely reassuring | Further testing with IgG-based antibodies, guided by a physician |
A raised tTG-IgA is a strong signal, but it is the start of a diagnosis rather than the end. Confirmation usually happens with a gastroenterologist, often through a gastroscopy with small tissue samples from the duodenum.
Keep eating gluten before you test
This is the single most important practical point about coeliac screening.
The antibodies only appear when your immune system is exposed to gluten. If you've cut gluten out, they fade, and the test can come back normal even if you have coeliac disease. The British Society of Gastroenterology recommends eating gluten regularly before testing, and suggests 3 to 6 grams of gluten a day for at least six weeks for anyone who has already reduced it ( Penny et al., 2026 ). For reference, 3 grams is roughly one and a half to two slices of wheat bread, or a fist-sized portion of cooked pasta.
If you're already avoiding gluten and feel better for it, talk to a physician before you test. Going gluten-free first and testing later is the most common reason coeliac disease stays hidden.
Who should consider coeliac screening
Guidelines recommend testing anyone with symptoms that could point to coeliac disease, and actively screening people in higher-risk groups ( Penny et al., 2026 ). You may want to consider coeliac screening if you:
- Have a parent, sibling, or child with coeliac disease
- Have type 1 diabetes or an autoimmune thyroid condition (such as Hashimoto's thyroiditis)
- Have iron deficiency or anaemia without a clear cause
- Have been diagnosed with irritable bowel syndrome (IBS)
- Have low bone density at a younger age than expected
- Experience persistent fatigue, bloating, or changes in bowel habits
- Have reduced gluten because you suspect it doesn't agree with you, and want to know whether coeliac disease is the reason. Talk to a physician first, because the test only works if you're eating gluten regularly
That last group is larger than you might think. A reliable answer, from a test taken while you're eating gluten, changes what comes next. If you have coeliac disease, a strict gluten-free diet lets the gut lining heal and protects your long-term health. If you don't, you can make food choices based on how you feel, without a question mark hanging over them.
What happens after a diagnosis
A coeliac diagnosis can feel like a lot at first. The good news is that the treatment is clear: a lifelong gluten-free diet. For most people, symptoms like fatigue and bloating improve within weeks, while full healing of the gut lining typically takes one to two years or longer.
Follow-up usually includes:
- Support from a dietitian experienced in coeliac disease
- Repeat tTG-IgA tests to track how levels fall, alongside dietitian review
- Checks of iron, folate, vitamin B12, vitamin D, and calcium
- A bone density (DXA) scan about a year after diagnosis, since long-term malabsorption can affect bone health
- Pneumococcal vaccination, now recommended for all adults with coeliac disease
- An offer of testing for parents, siblings, and children
Your GP stays at the centre of this care. Screening simply gives you and your GP better information to start from.
Coeliac screening at Ahead Health
At Ahead Health, the coeliac screen is available as an add-on to our check-ups. It measures tTG-IgA and total IgA from the same blood sample as the rest of your panel, so there's no extra appointment or needle.
- Coeliac screen (add-on): Includes tTG-IgA and total IgA.
- Results: Reviewed by Swiss board-certified physicians and explained in your health report.
- If your result is raised: We explain what it means and recommend the right next step with a gastroenterologist or your GP. Keep eating gluten as usual until a specialist has confirmed the diagnosis.
FAQ
Can I test for coeliac disease if I already eat gluten-free?
Not reliably. The antibodies fade without gluten exposure, so a normal result could be misleading. Speak to a physician about a structured gluten challenge (usually 3 to 6 grams of gluten a day, roughly two to four slices of wheat bread, for at least six weeks) before testing. A genetic test (HLA-DQ2/DQ8) can sometimes rule coeliac disease out without a challenge. After a challenge, a specialist may prefer a biopsy to a blood test alone.
Does a positive coeliac screen mean I have coeliac disease?
A raised tTG-IgA makes coeliac disease likely, but the diagnosis is confirmed by a gastroenterologist. Depending on your levels and age, this may involve a gastroscopy with biopsy or a second blood test. Keep eating gluten as usual until then, because stopping early can make the confirmation tests unreliable.
Is coeliac disease the same as gluten intolerance?
No. Coeliac disease is an autoimmune condition with measurable antibodies and intestinal damage. Non-coeliac gluten sensitivity causes symptoms without that damage and has no specific blood test. Coeliac screening tells you whether coeliac disease is likely, but it can't diagnose gluten sensitivity or wheat allergy.
