Bolsonaro was admitted to AdventHealth Celebration hospital in the US state of Florida with severe abdominal pain earlier this week.
In late December, Bolsonaro went to the US to spend New Year's Eve at former US President Donald Trump's Mar-a-Lago resort in Florida.
Bolsonaro neither participated in the inauguration of his successor Luiz Inacio Lula da Silva on January 1 nor intended to hand over the presidential sash.
Reports of Bolsonaro's hospitalization came a day after thousands of his supporters stormed the National Congress building, the Palacio do Planalto and the Brazilian Supreme Court in protest of the presidential election results.
Bolsonaro has had health problems since an assassination attempt in 2018, when he was stabbed during a campaign rally in the town of Juiz de Fora, about 125 miles north of Rio de Janeiro, nearly a month before the election. The knife damaged the mesenteric artery, which provides blood supply to the intestines. He underwent several surgeries afterward.