Symptoms of coeliac disease can range from mild to severe, and often come and go.

Mild cases may not cause any noticeable symptoms, and the condition is often only detected during testing for another condition.

Treatment is recommended even when symptoms are mild or non-existent, because complications can still occur.

Common symptoms

Diarrhoea is the most common symptom of coeliac disease. It's caused by the body not being able to fully absorb nutrients (malabsorption, see below).

Malabsorption can also lead to stools (poo) containing abnormally high levels of fat (steatorrhoea). This can make them foul smelling, greasy and frothy. They may also be difficult to flush down the toilet.

Other common gut-related symptoms include:

• abdominal pain
• bloating and flatulence (passing wind)
• indigestion
• constipation
• vomiting (usually only affects children)

And more general symptoms may include: 

• fatigue (extreme tiredness), which may be a sign of iron deficiency anaemia or vitamin B12 folate deficiency anaemia
• unexpected weight loss
• an itchy rash (see below) 
• difficulty getting pregnant 
• tingling and numbness in your hands and feet (peripheral neuropathy)
• disorders that affect co-ordination, balance and speech (ataxia)
• swelling of the hands, feet, arms and legs caused by a build-up of fluid (oedema)

Malnutrition

If coeliac disease is not treated, not being able to digest food in the normal way could cause you to become malnourished, leading to tiredness and a lack of energy.

Malnutrition in children can result in failure to grow at the expected rate, both in terms of height and weight. Children may also have delayed puberty.

Dermatitis herpetiformis

Although not a symptom of coeliac disease, if you have an autoimmune response to gluten, you may develop a type of skin rash called dermatitis herpetiformis.

The rash is itchy and has blisters that burst when scratched. It usually occurs on your elbows, knees and buttocks, although it can appear anywhere on your body.

It's estimated that around 1 in 5 people with coeliac disease also develop dermatitis herpetiformis.

The exact cause of dermatitis herpetiformis is not known, but, as with coeliac disease, it's associated with gluten. Like coeliac disease, it should clear up after switching to a gluten-free diet.

Coeliac disease is caused by an abnormal immune system reaction to the protein gluten, which is found in foods such as bread, pasta, cereals and biscuits.

It's an autoimmune condition, where the immune system mistakes healthy cells and substances for harmful ones and produces antibodies against them (antibodies usually fight off bacteria and viruses).

In the case of coeliac disease, your immune system mistakes one of the substances that makes up gluten, called gliadin, as a threat to the body. The antibodies that are produced cause the surface of your intestine to become inflamed (red and swollen).

The surface of the intestine is usually covered with millions of tiny tube-shaped growths called villi. Villi increase the surface area of your gut and help it to digest food more effectively.

However, in coeliac disease, the damage and inflammation to the lining of the gut flattens the villi, reducing their ability to help with digestion.

As a result, your intestine is not able to digest the nutrients from your food, which causes the symptoms of coeliac disease.

Oats

Some people with coeliac disease may find that eating oats can trigger symptoms. This is because some oats may be contaminated by other grains during production.

Oats also contain a protein called avenin, which is similar to gluten. Most people with coeliac disease can safely eat avenin. However, there's some evidence to suggest a very small number of people may still be sensitive to products that are gluten-free and do not contain contaminated oats.

Increased risk

It's not known why people develop coeliac disease. It also is not clear why some have mild symptoms while others have severe symptoms.

However, the factors described below are known to increase your risk of developing coeliac disease.

Family history

Coeliac disease often runs in families. If you have a close relative with the condition, such as a parent or sibling, your chance of also getting it is increased.

This risk is approximately 10% for those with a family history. If you have an identical twin with coeliac disease, there's a 75% chance you'll also develop the condition.

Research shows coeliac disease is strongly associated with a number of genetic mutations (abnormal changes to the instructions that control cell activity) that affect a group of genes called the HLA-DQ genes. HLA-DQ genes are responsible for the development of the immune system and may be passed down through a family.

However, mutations in the HLA-DQ genes are common and occur in about one-third of the population. This suggests that something else, such as environmental factors, must trigger coeliac disease in certain people.

Environmental factors

You're more likely to develop coeliac disease if you had a digestive system infection (such as a rotavirus infection) during early childhood.

Also, there's evidence that introducing gluten into your baby's diet before they're 3 months old may increase their risk of developing coeliac disease.

Most experts recommend waiting until your child is at least 6 months old before giving them food containing gluten.

There might also be an increased chance of babies developing coeliac disease if they're not being breastfed when gluten is introduced into the diet.

Read more about your baby's first solid foods.

Other health conditions

A number of other health conditions can increase your risk of developing coeliac disease, including:

• type 1 diabetes
• thyroid conditions 
• ulcerative colitis – a digestive condition that causes inflammation of the colon (large bowel)
• neurological disorders (which affect the brain and nervous system) such as epilepsy
• Down's syndrome and Turner syndrome

It's unclear whether these health conditions directly increase your risk of developing coeliac disease, or whether they and coeliac disease are both caused by another, single underlying cause.

Routine testing for coeliac disease is not recommended unless you have symptoms or an increased risk of developing them.

Testing for coeliac disease involves having:

• blood tests – to help identify people who may have coeliac disease
• a biopsy – to confirm the diagnosis

While being tested for coeliac disease, you'll need to eat foods containing gluten to ensure the tests are accurate. You should also not start a gluten-free diet until the diagnosis is confirmed by a specialist, even if the results of blood tests are positive.

Blood test

Your GP will take a blood sample and test it for antibodies usually present in the bloodstream of people with coeliac disease.

You should include gluten in your diet when the blood test is carried out because avoiding it could lead to an inaccurate result.

If coeliac disease antibodies are found in your blood, your GP will refer you for a biopsy of your gut.

However, it's sometimes possible to have coeliac disease and not have these antibodies in your blood.

If you continue to have coeliac disease-like symptoms despite having a negative blood test, your GP may still recommend you have a biopsy.

Biopsy

A biopsy is carried out in hospital, usually by a gastroenterologist (a specialist in treating conditions of the stomach and intestines). A biopsy can help confirm a diagnosis of coeliac disease.

If you need to have a biopsy, an endoscope (a thin, flexible tube with a light and camera at one end) will be inserted into your mouth and gently passed down to your small intestine.

Before the procedure, you'll be given a local anaesthetic to numb your throat and perhaps a sedative to help you relax.

The gastroenterologist will pass a tiny biopsy tool through the endoscope to take samples of the lining of your small intestine. The sample will then be examined under a microscope for signs of coeliac disease.

Tests after diagnosis

If you're diagnosed with coeliac disease, you may also have other tests to assess how the condition has affected you so far.

You may have further blood tests to check the levels of iron and other vitamins and minerals in your blood. This will help determine whether coeliac disease has led to you developing anaemia (a lack of iron in your blood) as the result of poor digestion.

If you appear to have dermatitis herpetiformis (an itchy rash caused by gluten intolerance), you may have a skin biopsy to confirm it. This will be carried out under local anaesthetic, and involves a small skin sample being taken from the affected area so it can be examined under a microscope.

A DEXA scan may also be recommended in some cases of coeliac disease. This is a type of X-ray that measures bone density. It may be necessary if your GP thinks your condition may have started to thin your bones.

In coeliac disease, a lack of nutrients caused by poor digestion can make bones weak and brittle (osteoporosis). A DEXA scan is not a test for arthritis, and only measures bone density to see whether you're at risk of bone fractures as you get older.

Local groups

Many people feel overwhelmed when they're first diagnosed with coeliac disease. Switching to a gluten-free diet can be confusing, particularly if you've been eating foods that contain gluten for many years.

In the first few months after being diagnosed, many people accidentally eat foods that contain gluten, which may trigger a return of their symptoms.

You can learn more about coeliac disease and receive practical advice about switching to a gluten-free diet by contacting your local coeliac disease support group.

Support groups provide help and support for people with coeliac disease, including those recently diagnosed and those who've been living with the condition for years.

The Coeliac UK website provides further information as well as advice and details of support groups in your area.

NICE guidance

The 2015 guidance published by the National Institute for Health and Care Excellence (NICE) provides details about when testing for coeliac disease should be carried out.

Adults or children should be tested if they have the following signs or symptoms:

• persistent unexplained gastrointestinal symptoms, such as feeling sick and being sick
• faltering growth
• prolonged fatigue (feeling tired all the time)
• unexpected weight loss
• severe or persistent mouth ulcers
• unexplained iron deficiency anaemia, vitamin B12 or folate deficiency anaemia
• type 1 diabetes, at diagnosis
• autoimmune thyroid disease (an underactive thyroid or overactive thyroid), at diagnosis
• irritable bowel syndrome (IBS) (in adults)

Testing is also recommended if you have a first-degree relative (parent, sibling or child) with coeliac disease.

Read the NICE guidance about the recognition, assessment and management of coeliac disease.

Coeliac disease is usually treated by simply excluding foods that contain gluten from your diet.

This prevents damage to the lining of your intestines (gut) and the associated symptoms, such as diarrhoea and stomach pain.

If you have coeliac disease, you must give up all sources of gluten for life. Your symptoms will return if you eat foods containing gluten, and it will cause long-term damage to your health.

This may sound daunting, but your GP can give you help and advice about ways to manage your diet. Your symptoms should improve considerably within weeks of starting a gluten-free diet. However, it may take up to 2 years for your digestive system to heal completely.

Your GP will offer you an annual review during which your height and weight will be measured and your symptoms reviewed. They'll also ask you about your diet and assess whether you need any further help or specialist nutritional advice.

A gluten-free diet

When you're first diagnosed with coeliac disease, you'll be referred to a dietitian to help you adjust to your new diet without gluten. They can also ensure your diet is balanced and contains all the nutrients you need.

If you have coeliac disease, you'll no longer be able to eat foods that contain barley, rye or wheat, including farina, graham flour, semolina, durum, cous cous and spelt.

Even if you only consume a small amount of gluten, such as a spoonful of pasta, you may have very unpleasant intestinal symptoms. If you keep consuming gluten regularly, you'll also be at greater risk of developing osteoporosis and cancer in later life.

Read more about complications of coeliac disease.

As a protein, gluten is not essential to your diet and can be replaced by other foods. Many gluten-free alternatives are widely available in supermarkets and health food shops, including pasta, pizza bases and bread. Some GPs may provide gluten-free foods on prescription.

Many basic foods – such as meat, vegetables, cheese, potatoes and rice – are naturally free from gluten so you can still include them in your diet. Your dietitian can help you identify which foods are safe to eat and which are not. If you're unsure, use the lists below as a general guide.

Foods containing gluten (unsafe to eat)

If you have coeliac disease, do not eat the following foods, unless they're labelled as gluten-free versions:

• bread
• pasta
• cereals
• biscuits or crackers
• cakes and pastries
• pies
• gravies and sauces

It's important to always check the labels of the foods you buy. Many foods – particularly those that are processed – contain gluten in additives, such as malt flavouring and modified food starch.

Gluten may also be found in some non-food products, including lipstick, postage stamps and some types of medication.

Cross-contamination can occur if gluten-free foods and foods that contain gluten are prepared together or served with the same utensils.

Gluten-free foods (safe to eat)

If you have coeliac disease, you can eat the following foods, which naturally do not contain gluten:

• most dairy products, such as cheese, butter and milk
• fruit and vegetables
• meat and fish (although not breaded or battered)
• potatoes
• rice and rice noodles
• gluten-free flours, including rice, corn, soy and potato

By law, food labelled as gluten free can contain no more than 20 parts per million (ppm) of gluten.

For most people with coeliac disease, these trace amounts of gluten will not cause a problem. However, a small number of people are unable to tolerate even trace amounts of gluten and need to have a diet completely free from cereals.

The Coeliac UK website has more about the law on gluten-free, as well as information and advice about a gluten-free diet and lifestyle.

Oats

Oats do not contain gluten, but many people with coeliac disease avoid eating them because they can become contaminated with other cereals that contain gluten.

There's also some evidence to suggest that a very small number of people may still be sensitive to products that are gluten-free and do not contain contaminated oats. This is because oats contain a protein called avenin, which is suitable for the majority of people with coeliac disease, but may trigger symptoms in a few cases.

If, after discussing this with your healthcare professional, you want to include oats in your diet, check the oats are pure and that there's no possibility contamination could have occurred.

You should avoid eating oats until your gluten-free diet has taken full effect and your symptoms have been resolved. Once you're symptom free, gradually reintroduce oats into your diet. If you develop symptoms again, stop eating oats.

Advice on feeding your baby

Do not introduce gluten into your baby's diet before they're 6 months old. Breast milk is naturally gluten free as are all infant milk formulas.

If you have coeliac disease, Coeliac UK recommends foods containing gluten are introduced gradually when a child is 6 months old. This should be carefully monitored. 

The Coeliac UK website provides support for parents.

Other treatments 

As well as eliminating foods that contain gluten from your diet, a number of other treatments are available for coeliac disease. These are described below.

Vaccinations

In some people, coeliac disease can cause the spleen to work less effectively, making you more vulnerable to infection.

You may therefore need to have extra vaccinations, including:

• flu (influenza) jab
• Hib/MenC vaccine, which protects against sepsis (blood poisoning), pneumonia and meningitis (an infection of the lining of the brain)
• pneumococcal vaccine, which protects against infections caused by the Streptococcus pneumoniae bacterium

However, if your spleen is unaffected by coeliac disease, these vaccinations are not usually necessary.

Supplements

As well as cutting gluten out of your diet, your GP or dietitian may also recommend you take vitamin and mineral supplements, at least for the first 6 months after your diagnosis.

This will ensure you get all the nutrients you need while your digestive system repairs itself. Taking supplements can also help correct any deficiencies, such as anaemia.

Dermatitis herpetiformis

If you have dermatitis herpetiformis (an itchy rash that can be caused by gluten intolerance), cutting gluten out of your diet should clear it up.

However, it can sometimes take longer for a gluten-free diet to clear the rash than it does to control your other symptoms, such as diarrhoea and stomach pain.

If this is the case, you may be prescribed medication to speed up the healing time of the rash. It's likely that this will be a medicine called Dapsone, which is usually taken orally (in tablet form) twice a day.

Dapsone can cause side effects, such as headaches and depression, so you'll always be prescribed the lowest effective dose.

You may need to take medication for up to 2 years to control dermatitis herpetiformis. After this time, you should have been following a gluten-free diet long enough for the rash to be controlled without the need for medication.

Refractory coeliac disease

Refractory coeliac disease is a rarer type of coeliac disease where the symptoms continue, even after switching to a gluten-free diet. The reasons for this are unclear.

It's estimated that around 1 in every 140 people with coeliac disease will develop the refractory form of the condition.

If refractory coeliac disease is suspected, it's likely you'll be referred for a series of tests to make sure your symptoms are not being caused by another condition.

If no other cause can be found and the diagnosis is confirmed, you'll be referred to a specialist. Treatment options include steroid medication (corticosteroids), such as prednisolone, which help block the harmful effects of the immune system.

If you have coeliac disease, it's crucial you do not eat any gluten. If you have untreated or undiagnosed coeliac disease and you're still eating gluten, several complications can occur.

It's a common misconception that eating a little gluten will not harm you. Eating even tiny amounts can trigger symptoms of coeliac disease and increase your risk of developing the complications outlined below.

Malabsorption

Malabsorption (where your body does not fully absorb nutrients) can lead to a deficiency of certain vitamins and minerals. This can cause conditions such as:

• iron deficiency anaemia
• vitamin B12 and folate deficiency anaemia
• osteoporosis – a condition where your bones become brittle and weak

Malnutrition

As coeliac disease causes your digestive system to work less effectively, severe cases can sometimes lead to a critical lack of nutrients in your body. This is known as malnutrition, and can result in your body being unable to function normally or recover from wounds and infections.

If you have severe malnutrition, you may become fatigued, dizzy and confused. Your muscles may begin to waste away and you may find it difficult to keep warm. In children, malnutrition can cause stunted growth and delayed development.

Treatment for malnutrition usually involves increasing the number of calories in your diet and taking supplements.

Read more about treating malnutrition.

Lactose intolerance

If you have coeliac disease, you're more likely to also develop lactose intolerance, where your body lacks the enzyme to digest the milk sugar (lactose) found in dairy products. Lactose intolerance causes symptoms such as bloating, diarrhoea and abdominal discomfort.

Unlike gluten in coeliac disease, lactose does not damage your body. But you may get some gut-related symptoms when you eat foods containing lactose because you can't digest it properly.

Lactose intolerance can be effectively treated by not eating and drinking dairy products that contain lactose. You may also need to take calcium supplements – dairy products are an important source of calcium, so you'll need to compensate for not eating them.

Read more about treating lactose intolerance.

Cancer

Cancer is a very rare but serious complication of coeliac disease.

Someone with coeliac disease has a slightly increased risk of developing certain cancers. Recent research shows that this increased risk is less than previously thought.

Cancers associated with coeliac disease are small bowel cancer, small bowel lymphoma and Hodgkin lymphoma. However, most people with coeliac disease will not develop any of these.

If you've been following a gluten-free diet for 3 to 5 years, your risk of developing these types of cancer is the same as that of the general population.

Coeliac disease in pregnancy

Poorly controlled coeliac disease in pregnancy can increase the risk of developing pregnancy-related complications, such as giving birth to a baby with a low birthweight.

Coeliac UK has more information and advice about coeliac disease and pregnancy. You can also read more about healthy eating in pregnancy.