President Michael D Higgins remained in hospital overnight following tests, however he was said to be in "excellent spirits".
President Higgins, 82, was brought to hospital for precautionary tests after feeling unwell yesterday evening.
In a statement, Áras an Uachtaráin said that he was initially assessed at the Áras where "no immediate concerns were identified but a decision was made to proceed to hospital in order to undergo tests, the initial results of which have been positive.
"The President, who will remain in hospital overnight, is in excellent spirits and has thanked the medical staff for the care he has received."
On Wednesday night, President Higgins presented the 2024 Volta award to British film director Steve McQueen, at the Dublin International Film Festival.
Earlier that day, he received a courtesy call from Bui Thanh Son, the Minister for Foreign Affairs of Vietnam.
He also met Peter Pellegrini, Speaker of the National Council of the Slovak Republic and a parliamentary delegation to Áras an Uachtaráin.
