"The honourable Chief Minister of Tamil Nadu is under observation," a medical bulletin from Apollo Hospitals Chief Operating officer Subbiah Viswanathan said.
Jayalalithaa was on a 'normal diet,' he added.
Jayalalithaa was admitted to the corporate hospital here late Thursday after she complained of fever and dehydration.
Prime Minister Narendra Modi, Governor Ch Vidyasagar Rao, DMK leaders M Karunanidhi and M K Stalin and Chief Ministers of Karnataka and Puducherry, Siddaramaiah and V Narayanasamy respectively, were among others who had wished speedy recovery to the 68-year-old AIADMK chief.