Letterkenny University Hospital has implemented its Full Capacity Protocol due to overcrowding this week.
The measure comes as 138 people sought care at the Emergency Department in the past day.
This is a significantly higher than average number, which has led to delays and a high number of patients on trolleys.
Forty-seven people were recorded awaiting admission on trolleys this Tuesday morning.
Staff are currently making efforts to identify patients who are appropriate for discharge in order to deal with the overcrowding.
A Saolta spokesperson said: “Hospital management apologises for the inconvenience and distress that these delays cause patients and their families. The hospital prioritises those in most need of care and this may lead to delays for less urgent patients.
“We would like to remind the public that we encourage them to attend the Emergency Department only in the case of real emergencies and they should contact their GP or GP Out-of-Hours service in the first instance.
“We are committed to treating everyone who presents at our ED but we do so strictly in order of medical priority and apologise for the long wait times currently.
“We would like to thank our staff who are working extremely hard at this time.”