Fourteen people have had their cancer surgeries postponed in the Western Health Trust this week due to a surge in Covid-19 patients.
The trust confirmed to BBC News NI that 14 patients required overnight stays on Monday and Tuesday, which was not possible.
A trust spokesperson said they are working to rebook these surgeries at the earliest opportunity.
The trust is currently in the "level red" stage of their Covid surge plan.
The Western Trust confirmed that cancer surgery in day case theatres were not affected on these dates and inpatient cancer surgery went ahead on Wednesday.
In a statement, a Western Trust spokesperson said: "We continue to monitor the situation on a daily basis.
"We sincerely apologise to any patient who had their surgery postponed and have been affected by this decision."
These delays come at a time when the health service is currently facing staffing shortages, with an estimated 2,700 NI healthcare workers currently self-isolating as a result of Covid-19.
The figures, from the six health trusts, are a significant increase from a fortnight ago when BBC News NI reported that 1,200 staff were isolating across all the trusts.
Speaking at a press conference at Stormont on Wednesday, Health minister Robin Swann said that "within days we will exceed the highest number of hospital admissions experienced in the first wave."
"If no full lockdown is imposed, restrictions have to be targeted however complicated that may be.
"I have yet to see any real or feasible alternatives to the actions we are taking," Mr Swann said.
The minister said if people did not follow the public health guidance, many more avoidable deaths would occur.
On Wednesday, Northern Ireland reported 1,039 new coronavirus cases, bringing the total number of cases to 29,992.
There was also five further Covid-19 related deaths were reported, bringing the total death toll to 629.
In the Republic of Ireland there were three additional deaths related to Covid-19 reported on Wednesday.
It brings the total number of deaths in the country to 1,868.
As of midnight on Tuesday, the Irish Department of Health reported 1,167 new cases of Covid-19, bringing the total number of confirmed cases to 53,422.