The Emergency Department at UHG is the most overcrowded in Ireland today with 42 people on trolleys.
After UHG the worst affected hospitals today are Cork University Hospital (41), Beaumont Hospital (37), and Limerick University Hospital (36).
The Irish Nurses and Midwives Organisation Trolley/Ward Watch keeps track of the number of people waiting on trolleys at the A&E or without a proper bed in overcrowded wards.
Galway dealt with strenuous conditions this week as an escalation protocol was put in place on Tuesday in the city and at Portiuncula due to serious overcrowding.
The two hospitals were dealing with an upsurge in flu and respiratory illnesses that require patients to be kept in isolation.