Essebsi's office announced his hospitalization Thursday. The president also was briefly hospitalized last week.
Essebsi won office in 2014 in the wake of the country's Arab Spring uprising.
He recently announced he wouldn't run in the election set for November, saying a younger person should lead the country. Essebsi has seemed increasingly frail during recent appearances.
If the president is incapacitated, Tunisia's Constitution calls for the president of parliament to take over until an election is held.
Essebsi's centrist movement presents itself as a bulwark against Islamic extremism and a beacon of stability amid the rocky transition to democracy in Tunisia.
However, the president has been unable to calm the political and economic chaos that have plague Tunisia. Twin suicide bombings were carried out Thursday in the capital, Tunis.
Lawmaker Mustafa Ben Ahmed sought to calm fears about the president's health and the country's leadership.
"We wish him well. We have the Tunisian Constitution that guides us in all that is necessary in the absence of the president," he said.
Mehdi El Arem in Tunis and Lori Hinnant in Paris contributed.
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