If you have coeliac disease, it's crucial you don't 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 won't 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 doesn't fully absorb nutrients) can lead to a deficiency of certain vitamins and minerals. This can cause conditions such as:

Click on the links above for more information about the symptoms and treatments of these conditions.

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 doesn't 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 – as dairy products are an important source of calcium, you'll need to compensate for not eating them.

Read more about treating lactose intolerance.

Cancer

Some research has suggested that having coeliac disease can increase your risk of developing certain types of cancer, including bowel cancer and lymphoma (cancer of the lymphatic system, which is part of the immune system).

The same research found people with coeliac disease have a lower risk of developing lung cancer and breast cancer, although the reasons for this are unclear.

It's estimated that people with coeliac disease are twice as likely to develop bowel cancer than the general population.

However, this is still a very small increase in risk – only one in every 200 people with coeliac disease will develop bowel cancer in the first 10 years after diagnosis.

The risk of developing cancer is thought to be highest during the first year after diagnosis, before dropping to normal as your gluten-free diet starts to take effect.

Whether or not you have coeliac disease, it's important to be aware of the symptoms of bowel cancer, which include:

  • blood in stools (faeces)
  • unexplained weight loss 
  • changes in your normal bowel habit that last more than four weeks 

See your GP if you develop these symptoms.

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 birth weight.

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

Page last reviewed: 04/12/2016

Next review due: 04/12/2019