Three hospitals in Carlow, Tipperary and Westmeath are at the centre of industrial disputes over staffing levels.
Nurses at the Sacred Heart Hospital in Carlow have voted in favour of industrial action in a dispute on staffing levels.
The Irish Nurses' Organisation said the policy of only replacing a nurse on sick leave after seven days absence places a huge workload on staff and threatens standards of care.
Nursing staff in Cashel, Co Tipperary are expected to ballot for industrial action this week.
The INO said the staff at Our Lady's Hospital are in dispute over inadequate staffing levels especially in operating theatres.
Staffing levels in at the Midlands Regional Hospital in Mullingar are at the centre of a dispute by theatre nurses who have begun a work-to-rule action.
The INO claims conditions in theatres are unsafe because the Midland Health Board has cut the number of nurses working at any one time, from three to two.
The action is expected to go for three days and may be escalated if progress is not made at talks in the Labour Relations Commission tomorrow.