Aides to the "first girlfriend" said she had been admitted on Friday "for a rest and to undergo some tests," and was expected to leave hospital tomorrow.
Closer magazine reported on Friday that Hollande, 59, has been having an illicit affair with actress Julie Gayet, 41.
The weekly glossy printed photos which appeared to show Gayet and Hollande arriving separately at a flat near the presidential Elysee Palace for secret trysts.
Hollande, who was reportedly delivered to the flat on a chauffeur-driven scooter, has slammed the report as an outrageous attack on his right to a private life but has not denied the substance of Closer's claims.