The hospital surge plan is in place at Cork University Hospital (CUH) due to rising Covid-19 cases putting services under "significant pressure".
In a statement, hospital management warned people to expect delays in the emergency department which has been "exceptionally busy" in recent weeks.
A number of non-urgent procedures will be cancelled due to "the increasing number of Covid-19 positive patients admitted to the hospital".
CUH management said: "The Hospital Surge Plan is currently being implemented and unfortunately this may result in the cancellation of a number of non-urgent procedures. Patients will be contacted directly in the event of their procedure being cancelled.
"Hospital management have requested that, where appropriate, the public contact their GP/South Doc in the first instance and explore all other options available to them prior to attending the Emergency Department if their needs are not urgent. Patient care is paramount in CUH and this situation is being treated as a priority by Hospital Management who have taken steps to address this issue."
Taoiseach Micheál Martin is due to announce increased Covid measures on Tuesday, aimed at tackling rising infection rates.
A midnight curfew for pubs, restaurants and nightclubs is expected to be on the way, in addition to calls for people to work from home where possible.
Cabinet met on Tuesday afternoon to finalise the plans after receiving stark warnings from public health officials as to how the current wave of infections will impact the health service.
