A new online assessment tool will help identify Australians living with coeliac disease.

It's feared more than a quarter of a million Australians have coeliac disease and don't know it.

Coeliac Australia says it estimates one in 70 Australians have coeliac disease but 80 per cent are undiagnosed.

To combat this they are launching a new online assessment tool to help identify those suspected of living with the serious disease of the bowel.

Coeliac Australia president Michael Bell says the health and wellbeing of tens of thousands of Australians can be improved once diagnosed and they start a gluten-free diet.

People with coeliac disease are unable to eat gluten - a protein found in wheat, barley, rye and oats. Currently there is no cure and the only treatment is a strict gluten free diet for life.

If left untreated coeliac disease can cause chronic ill health and lead to liver disease and cancer of the bowel.

The typical symptoms of coeliac disease include; gastrointestinal upsets, anaemia and nutrient deficiencies, fatigue and joint pain.

People who suspect they may be at risk of coeliac disease can now take the quick assessment at www.coeliac.org.au/assess on Coeliac Australia's website.

If risk factors are identified, the participant can download a letter to take to their GP with details of their assessment.

"If your assessment reveals that your symptoms are related to coeliac disease, discuss the results with your doctor and follow their expert medical advice," Mr Bell said.

It is still essential that people continue to eat foods containing gluten until their doctor confirms a diagnosis of coeliac disease, Mr Bell added.