The INMO says full-scale industrial action by nurses will be considered if the HSE does not address issues over pay and staff levels.
The nursing union said it will meet on Wednesday to consider all options.
They are holding an hour-long protest at Connolly Hospital in Dublin today to highlight what they say are "unsafe staffing levels".
Similar protests took place earlier this month at hospitals around the country.
Lorraine Monaghan, the INMO Industrial Relations Officer, said: "The INMO is not ruling out industrial action, we have a special delegate conference on Wednesday and our members throughout the country will discuss the Public Service Pay Commission report and will consider the next steps.
"But we have not ruled out industrial action."