People with coeliac disease are waiting an average of 13 years to be diagnosed, a poll has revealed.
The gut disorder is caused by gluten intolerance, and can lead to bone problems, infertility or bowel cancer.
The charity Coeliac UK says some of the 800 patients surveyed reported seeing their GP almost 30 times before being diagnosed.
But it says the condition can be easily detected by GPs using a quick and simple blood test.
People with coeliac disease can experience a range of symptoms, including as bloating, diarrhoea, chronic fatigue, breathlessness, depression and weight gain.
Children with the condition can have behavioural, learning or concentration problems.
The only treatment for the condition is a life-long gluten-free diet.
The poll was part of research carried out for Coeliac UK by the University of Oxford.
It also found patients often have to insist on being given the blood test, which is the first step to diagnosis.
In addition, 29% of those polled said that prior to diagnosis, they experienced extreme pain, falling to 5% after diagnosis.
Anxiety levels fell from 13% to 3%.
Norma Mc Gough, head of diet at Coeliac UK, said the delays in diagnosis were a combination of patients not recognising, or getting used to, their symptoms - or that doctors were not considering coeliac disease as an explanation for what could be a vague range of symptoms.
Coeliac UK chief executive Sarah Sleet said: "Coeliac disease is considered to be the most under-diagnosed common chronic condition in the UK today.
"One in 100 are believed to be at risk from the condition, but the latest research suggests only one in eight, or 12.5%, of these have been diagnosed.
"And yet, it is easy to diagnose with inexpensive blood tests available to quickly identify cases in primary care.
"There is no reason why people should not be diagnosed more quickly, and avoid years of debilitating pain and ill-health."
Professor Mayur Lakhani, head of the Royal College of GPs said: "I am sorry to hear of the experience of some patients in this report who have had a late diagnosis.
"Awareness of coeliac disease is increasing but doctors do find it a difficult condition to consider for diagnosis as its symptoms are also mimicked by many other common disorders.
"However, more needs to be done and can be done. I would urge all doctors to be more vigilant about this condition and to request the simple blood test which can clinch an early diagnosis."