Suharto, who ruled the world's fourth-most populous country for 32 years, stepped down in 1998 amid political upheaval and an economic crisis that triggered widespread opposition to his government.
Kidney function 'worsening'
Mardjo Soebiandono, head of the medical team treating Suharto, said that his patient's kidney function was worsening and there was excessive liquid in his lungs.
Born June 8, 1921
Served as general in Indonesian army
Seized power from Indonesia's first president Sukarno in 1965
Established 'New Order' government characterised by strong central government and repression of dissent
Forced to resign in 1998 amid widespread protests triggered by Asian financial crisis
"The condition of Mr Suharto has not improved on the second day of hospital treatment," Soebiandono told a news conference.
"His blood pressure is higher than this morning, so we were able to start putting him on haemodialysis. Hopefully we can recover his kidney function soon."
The former political and military leader is to receive more intensive treatment and closer monitoring.
Suharto has been hospitalised on a number of occasions in recent years suffering from various problems, including intestinal bleeding and strokes.
Djoko Rahardjo, Suharto's chief physician, said the former general was conscious but his condition was worse than on previous occasions.
"We are trying our best," he said, adding that Suharto had told his family he did not want to be taken overseas for treatment.
Suharto, who came to power after a botched 1965 coup attempt that was blamed on communists, has lived in seclusion in Jakarta's Menteng neighbourhood since he stepped down.
After he was pushed from power, Suharto was put on trial on charges of embezzling hundreds of millions of dollars in state money, but the government dropped the case due to his poor health.
However, a civil suit is currently being heard over the charges. The government is seeking $1.4bn in damages and returned assets allegedly accrued through a charitable foundation Suharto chaired while in power.