Chief Medical Officer Dr Tony Holohan has undergone tests in hospital that are unrelated to Covid-19.
Dr Holohan said he expects to be discharged tomorrow morning and to be back at work shortly afterwards.
He gave details of his admission to RTÉ News after he appeared to become unwell during the daily Department of Health news conference last night.
In a phone conversation, Mr Holohan said that he went to St James's Hospital in Dublin last night where he underwent some tests not related to the coronavirus infection.
Mr Holohan said that in the meantime, Deputy Chief Medical Officer Dr Ronan Glynn will take over in his absence and lead today's press conference.
This evening, Dr Glynn said that Dr Holohan hoped to be back in work tomorrow.