Former Taoiseach Brian Cowen has been hospitalised after becoming seriously ill in recent days.
Mr Cowen is understood to be receiving treatment in a Dublin hospital after concerns for his health arose.
He is believed to have checked into hospital on Thursday and was continuing to receive treatment yesterday.
Mr Cowen's family would like the matter to be treated as privately as possible.
Yesterday a number of Mr Cowen's Fianna Fail colleagues wished the former Taoiseach a speedy recovery and a return to full health.
Taoiseach Leo Varadkar also said he hoped that Mr Cowen makes a full recovery after learning he had fallen ill.
Speaking at an event in Longford, Mr Varadkar said: "I served in the Dail with Brian Cowen for a number of years and I really hope if he is unwell, as I hear he is, that he makes a speedy recovery."
Meanwhile, long-serving Fianna Fail TD and former minister Willlie O'Dea also said he hoped Mr Cowen recovered as soon as possible.
"I've known Brian since he was one of my students in UCD and we were great friends in politics too," Mr O'Dea said.
"I hope he gets well very soon and makes a full recovery."
Former Fianna Fail deputy leader Eamon O Cuiv said his thoughts were with Mr Cowen and his family.
"I wish him a very speedy recovery and full recovery and I think it is well-known I have great respect for what he did during a very difficult time for this country," Mr O Cuiv said.
"My thoughts are with him and his family at this difficult time."
Justice Minister Charlie Flanagan, who shared a constituency with Mr Cowen for many years, said he was "very sorry to hear" his former Dail colleague had fallen ill.
On Twitter Mr Flanagan wrote: "I wish himself and his family well at this anxious time and worrying time."
Mr Cowen was also taken to hospital in May when he became sick at an Oireachtas golf event. He was reportedly taken by ambulance to Limerick Regional Hospital after becoming unwell at the event in Lahinch Golf Club in Clare.
He had since recovered and attended public events including the funeral of GAA legend Eugene McGee.
Mr Cowen has kept a relatively low profile since stepping down from national politics. He is married to Mary and is a father of two daughters, Sinead and Meadhbh.
Along with other former Taoisigh, he attended a ceremony for Pope Francis in Dublin Castle during the Papal State visit to Ireland last year.
In 2017 he was awarded an honorary doctorate by the National University of Ireland.
During a speech at the event, he criticised the EU over its role in the financial crisis and defended measures Fianna Fail introduced during the crash.
Last February he criticised Britain's approach to the Brexit negotiations during an appearance at a meeting of the Diversity Europe Group of the European Economic Social Committee held at Queen's University in Belfast.
He said the view of certain Conservative Party MPs on the controversial backstop was "unreasonable".