The Canberra Hospital's gastroenterology unit had been unable to cope with demand and was transferring patients to Queanbeyan for their colonoscopies, tendering to find private doctors to do the procedures, and increasing the number of locum and weekend lists, she said.

On February 21 this year, 62 per cent of the 278 patients on the category 1 wait list had been waiting more than 30 days, figures released by Ms Fitzharris in response to questions from the Liberals show.

Of the 1442 category 1 patients treated in the eight months from July 2016 to February 2017, just 651, or 45 per cent, were seen in the recommended 30 days.

Another 209 were seen between 330 and 80 days, and 582 waited more than 80 days.

Ms Fitzharris's office did not provide information on what symptoms result in the urgent category 1 classification, but the NSW guidelines say category 1 patients are those with a high likelihood of significant pathology because of significant overt lower gastrointestinal bleeding, active inflammatory bowel disease or diarrhoea, clinically significant iron deficiency anaemia, or a positive faecal blood test.

Ms Fitzharris said the wait times were "of concern to ACT Health, and they are looking very hard at improving those waiting times".

Most patients referred to the specialist gastroenterologist at the hospital needed a colonoscopy. The unit had increased its number of colonoscopies in the past financial year, but "has been unable to keep up with the increased demand, resulting in a number of patients waiting longer than clinically recommended for their procedure".

The median waiting time across all categories of patient was 99 days.

Ms Fitzharris said there was no evidence of any detrimental impact on the community.

Colonoscopies and gastroscopies were prioritised by clinical urgency. If a patient's condition changed while they were waiting, GPs could request a review of their place on the waiting list.