Mohan Reddy, whose condition deteriorated on Friday morning, was admitted to the Asian Institute of Gastroenterology.
Mr Reddy, who served as a minister in the cabinets of both NT Rama Rao and N Chandrababu Naidu, was suffering from cancer. He is survived by a son.
He fell ill during the last month's by-election campaign in Yemmiganur assembly constituency in Kurnool district. He lost the by-poll.
He was elected from the same constituency for five consecutive times from 1983 to 1999.
He joined TDP when popular Telugu film star NT Rama Rao launched the party in 1982. A close confidante of NTR, he was an astrologer for both NTR and the party.
Mohan Reddy's body was shifted to his residence in Jubliee Hills here. Several TDP leaders paid their last respects.
His body would be shifted to his native Yemmiganur town, where the last rites will be performed on Saturday.