Hospitals in the Northern Trust have cancelled over 48,000 patient appointments in the last two years.
The revelation, disclosed by the Minister of Health, has led to fears of longer waiting times that could potentially affect thousands of patients across Mid Ulster.
The Trust - which includes both Magherafelt and Antrim Area Hospitals - had a total of 48,181 appointments cancelled by the hospitals themselves during the 2013/14 and 2014/15 financial years.
However it did see a small decrease in the number of outpatient clinics cancelled with 24,136 incidents falling to 24,045 in the last year.
Nevertheless the total number of cancelled appointments in the Northern Trust dwarfs that of the neighbouring Southern Trust which only saw 16,524 appointments cancelled in the last year.
This was the lowest number in Northern Ireland, but was an increase of over a thousand on the 2013/14.
The highest number took place in Belfast Trust where almost 160,000 appointments were cancelled in just two years.
One of the reasons for the high number is the extreme pressures faced by all Trust hospitals during the past winter.
The Department of Health described its own performance as “disappointing”, and revealed that 168,555 outpatient appointments were canceeled by hospitals across all five Health Trusts in 2014/15.
This compared to 167,230 the year before.
It also showed that 9,794 day case appointments, including ear nose and throat and dermatology treatments, were also cancelled.
The figures were released following a question to the Minister of Health by Alex Easton, MLA for North Down.