The Health Service Executive (HSE) is implementing recruitment controls.
It is understood managers have received a memo, saying no new staff can be hired unless others leave.
Last year, more than 4,500 new staff were hired.
Industry Correspondent with The Irish Times Martin Wall told Newstalk.com's Breakfast about the directive HSE boss Tony O'Brien has issued:
"The policy is going to be, there will be new interim controls, and the way it is spelled out is "X out before Y in". Now last night we asked the HSE and the working assumption is going to be one post will have to be supressed for one post to be created. So that is a fair bit of difference to 4,557 posts being created in in one year."
The Irish Times reports that interim employment controls kicked in at the beginning of this month: