Coeliac disease can be diagnosed at any age, and both children and adults can show symptoms
Delayed diagnosis is common. It can take an average of 13 years to diagnose.
Most people with coeliac disease have antibodies that show up in their blood. The first stage in diagnosis can be a blood test.
Who'll have a blood test
A blood test should be offered if you've any of the following:
- type 1 diabetes
- autoimmune thyroid disease
- dermatitis herpetiformis
- irritable bowel syndrome (IBS)
- anaemia without an obvious cause
- certain symptoms related to your digestive system – such as frequent diarrhoea, abdominal pain or vomiting, nausea or sudden weight loss
- close relatives (parents, siblings or children) with coeliac disease
A blood test might also be offered if:
- you feel tired all the time
- a child is not growing as fast as expected
- you've other symptoms or conditions that sometimes occur in people with coeliac disease – such as mouth ulcers, particular types of problems with your bones or liver, Down's syndrome, Turner syndrome or persistent constipation
Blood tests for coeliac disease are not recommended for infants who've not started to eat foods containing gluten.
Before a blood test
Before a blood test is taken, it's important that you eat gluten-containing foods in more than one meal every day for at least 6 weeks before the test.
What's involved in a blood test?
A blood test for coeliac disease involves taking a blood sample and testing it for antibodies in the blood.
You must have been eating gluten-containing food in more than 1 meal for at least 6 weeks before the test, for it to be successful.
Blood tests are 95% accurate at diagnosing coeliac disease.
If the coeliac antibodies are found in your blood, further investigation will be needed. This'll be discussed with you.
Your GP will refer you to your local coeliac service for confirmation of the diagnosis. You should remain on a normal diet until all investigations are complete.
It's sometimes possible to have coeliac disease and not have antibodies in your blood.
If you continue to have coeliac disease-like symptoms your GP may still refer you for a biopsy of your gut.
A biopsy can help confirm a diagnosis of coeliac disease.
If you're referred for a biopsy, this will be carried out in hospital. Usually, a biopsy will be done by a gastroenterologist. This is a doctor who specialises in treating conditions of the stomach and intestines.
What's involved in a biopsy?
If you need to have a biopsy, a thin flexible tube with a light called an endoscope will be inserted into your mouth or nose and passed down to your small intestine.
Before the procedure, a local anaesthetic is given to numb the throat and/or a sedative to help you relax.
During the procedure, the endoscopist 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.
For those under 16 years the endoscopy would be under an anaesthetic.
Diet before and after testing
You should continue to eat gluten-containing foods every day until a diagnosis has been confirmed.
A biopsy will only show coeliac disease if the person being tested has been eating gluten-containing foods regularly.
Only after coeliac disease is confirmed can you start a gluten-free diet.
If you're already on a gluten-free diet and find it hard to eat gluten again, your GP should refer you to a specialist. You may not be able to get gluten-free foods on prescription if you do not have coeliac disease confirmed by a biopsy.
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Tests after diagnosis
If you've been diagnosed with coeliac disease, you may also have other tests to assess how the condition has affected you so far.
Additional blood tests
You may have further blood tests to check levels of iron and other vitamins and minerals in your blood. This'll help check for anaemia.
Dual energy X-ray (DEXA) scan (adults only)
In coeliac disease, a lack of nutrients caused by poor absorption can make bones weak and brittle (osteoporosis).
A DEXA scan is a type of very low dose X-ray that measures bone density. This may be required if your risk score (FRAX/Qfracture) is high. This will be calculated as part of your assessment.
You can buy over-the-counter tests for coeliac disease at pharmacies. There isn't enough evidence that these tests are reliable.
If you've used one, it's important that you talk to your GP about the result.
Before a diagnosis can be confirmed, you'll still need to have a blood test and biopsy.