The Irish Nurses and Midwives Organisation has called for non-urgent procedures at Galway University Hospital to be cancelled immediately.
The hospital is experiencing its highest level of overcrowding since 2019, with 70 patients waiting on a bed.
A rising number of patients with Covid-19 at the facility is also increasing pressure on staff.
INMO industrial relations officer, Anne Burke, says staff shortages at Galway University Hospital, mean nurses are not able to provide timely care to patients.