The Mater Hospital in Dublin is appealing to people where possible, to avoid its emergency department.
The hospital is under significant pressure due to a combination of a high volume of patients, and an increased number of Covid-19 positive patients in the hospital, as well as staff who can't come to work due to contracting Covid or being a close contact.
Management at the facility is warning people who turn up at the emergency department with non-emergency conditions can expect long waits.
But it's advising anyone in need of emergency care will be treated.
Meanwhile, the number of patients being treated on trolleys at hospitals across the country has decreased slightly.
A total of 584 admitted patients are waiting for beds, down from a record high of 603 yesterday, according to the Irish Nurses and Midwives Organisation (INMO).
University Hospital Limerick remains the worst affected, with 75 patients on trolleys.
