Coeliac disease: symptoms, diagnosis and what to do after diagnosis

What is coeliac disease?

Coeliac disease, also known as celiac disease, is neither an allergy nor an intolerance: it is an autoimmune disease. In people with a genetic predisposition, gluten triggers the body’s own defence system to react against the small intestine.

This reaction inflames the lining and flattens the villi, the small folds through which nutrients are absorbed. As a result, you may lack iron, calcium or vitamins even if you eat well.

Gluten is a protein found in wheat, barley and rye, and in varieties of these grains such as spelt and kamut. The guide to food allergies and intolerances explains how coeliac disease differs from an allergy or intolerance.

What symptoms does it cause in adults and children?

Symptoms vary greatly from person to person, and some people have none. The best-known digestive symptoms are recurring diarrhoea, bloating, stomach pain or constipation [3].

Often, symptoms appear outside the intestine [3]:

• Iron-deficiency anaemia that does not resolve or keeps returning
• Lower-than-expected bone density, known as osteopenia or osteoporosis, or repeated fractures.
• Persistent tiredness and irritability
• An itchy, blistering skin rash called dermatitis herpetiformis.
• Recurring mouth ulcers and defects in tooth enamel.
• Periods that stop or elevated transaminases on a blood test

In children, growth may also slow. They may stop gaining weight or growing, be shorter than expected for their age, or reach puberty later [3]. In adults, iron deficiency is very common at diagnosis [4].

Coeliac disease should also be considered in certain groups even when there are no symptoms. These include first-degree relatives of someone with coeliac disease and people with type 1 diabetes, autoimmune thyroid disease or Down syndrome [3].

How is coeliac disease diagnosed?

The first step is a blood test for IgA tissue transglutaminase antibodies, ordered together with total IgA [1] [3]. Total IgA is measured because, if it is low, those antibodies may appear normal when they are not, and other tests are needed [1].

If the test is positive, a gastroenterologist will usually confirm the diagnosis with a biopsy. This is done during a gastroscopy, taking at least four samples from the duodenum, the first part of the small intestine [1].

In some children and adults with very high antibody levels—ten times the normal upper limit or more—the specialist may make the diagnosis without a biopsy [1] [3].

And here is the most important rule: all tests must be done while you are eating gluten. If you stop eating it beforehand, the blood test and biopsy may come back normal even if you have coeliac disease [1]. If you have already stopped, your doctor will advise you how and for how long to start eating it again [1].

Genetic testing for the HLA-DQ2 and DQ8 markers cannot diagnose coeliac disease on its own. It is reserved for uncertain cases and is mainly useful for ruling it out: if the result is negative, coeliac disease is very unlikely [1].

The first few weeks after diagnosis

Coeliac disease is treated by eating gluten-free for life, even when there are no symptoms. The margin is small. The accepted threshold for someone with coeliac disease is no more than 10 mg of gluten a day, far less than the amount in a slice of bread [4].

That is why checking the label is essential. By law, a food may be labelled “gluten-free” only if it contains 20 mg of gluten per kilo or less [2]. The “very low gluten” label allows up to 100 mg per kilo, so at home we stick to “gluten-free” [2].

If a product that should not contain gluten, such as rice or pulses, says it “may contain gluten”, leave it on the shelf.

Almost everything you buy fresh is already gluten-free; what you need to learn is how to read packaged food labels.

Oats deserve a special mention. Only oats certified gluten-free are suitable, because ordinary oats are often contaminated with wheat or barley during growing and milling [2]. If you tolerate them, guidelines allow you to include them from the time of diagnosis [4] [5].

At home, the risk comes from cross-contamination, when gluten passes from one food to another through contact [4]. Three steps can help a lot:

• Use a separate toaster, or toaster bags for gluten-free bread
• Clean the chopping board, colander and frying pan before preparing your food
• Use fresh frying oil that has not been used for battered foods containing gluten

The whole family does not need to eat gluten-free, but everyone should know these rules. For breakfast, options without bread such as sweet potato toast with guacamole and salmon can make things much easier.

Also ask to be referred to a registered dietitian. This visit is recommended from diagnosis onwards, to help you learn the gluten-free diet, check for deficiencies and make sure you get everything you need [4].

What follow-up care do you need?

At diagnosis, it is a good idea to have a blood test for deficiencies, including iron, folic acid, vitamin B12, vitamin D, calcium and other minerals [4]. Your doctor will treat any deficiencies. If you have anaemia, your doctor will prescribe iron. We adjust your diet to help prevent further deficiencies.

A bone density scan, which measures bone density, is recommended after a year on a gluten-free diet if you have risk factors. These include a late diagnosis, significant weight loss, severe malabsorption or fractures after minor knocks [4].

At follow-up appointments, antibody levels can help detect whether gluten is still getting into your diet. If they remain high, there is usually a source you have not spotted. If they are normal, that does not guarantee that the diet is perfect [4]. A follow-up biopsy is not routinely repeated [4].

Your first-degree relatives—that is, your parents, siblings and children—are more likely to have coeliac disease. They should have the blood test even if they feel well, and repeat it every few years if the result is normal [4].

And if the diagnosis feels overwhelming, asking for psychological support is not an overreaction. It can help you manage the diet and feel more at ease with it [4].

If your child has coeliac disease: home and school meals

In childhood, the diet and the goal are the same: to help your child grow and learn like everyone else. With a well-managed diet, their development usually does not differ from that of their classmates .

Food safety and nutrition law requires schools to provide gluten-free meals in school dining halls, with the diagnosis confirmed by a medical report [6].

Here is how to organise this in practice:

• Give the medical report to the school head and ask them to share it with the teacher, kitchen staff and supervisors.
• If a catering company runs the kitchen, ask for the gluten-free menu in writing and check it.
• Ask for your child to eat with their friends, not at a separate table
• Explain what they can eat and how to say no, in a way that suits their age

Birthdays and school trips need a little extra planning. Letting the other families know in advance and bringing a snack for your child helps ensure they are not left out.

Why do I still have symptoms if I eat gluten-free?

This is more common than it may seem, especially in the first few months. The intestine takes time to recover, and improvement can be slow in adults [4]. The first thing to check is whether gluten is still getting into your diet without you knowing, which is the usual cause [4].

If the diet is being followed correctly, your doctor will consider other causes [5]:

• Irritable bowel syndrome occurring alongside coeliac disease
• Lactose intolerance secondary to intestinal damage, which may improve as the lining heals.
• Small intestinal bacterial overgrowth (SIBO) or other intolerances, such as fructose intolerance.
• Other digestive causes that need investigation, such as microscopic colitis

When irritable bowel syndrome is also present and the intestine has recovered, a low-FODMAP diet may sometimes be tried. The elimination phase lasts 2 to 6 weeks, with an end date set from day one. Then reintroduce foods with a registered dietitian [4].

Very few people do not improve despite all this. This is known as refractory coeliac disease and is managed by a gastroenterologist [4].

What mistakes do we see in appointments?

• Filling the shopping trolley with ultra-processed “gluten-free” products. Gluten-free biscuits are still biscuits. The foundation is vegetables, fruit, pulses and gluten-free grains.
• Relaxing because “I don’t notice anything”. The intestine can react to gluten even when there are no symptoms.
• Ordering an omelette or chips at a café without asking. A shared fryer used for battered foods is a very common source of gluten.

And here is a question we often hear in appointments: does this go away over the years? Coeliac disease lasts a lifetime, but with a well-managed diet the intestine recovers and you can live a normal life .