"He (Mishra) has been admitted to the hospital," Director of the Rajendra Institute of Medical Sciences, Tulsi Mahto said here.
Mahto, however, did not spell out the exact nature of the illness.
Inspector General of Police Sailendra Singh said 76-year-old Mishra complained of some health problem at the Birsa Munda Central Jail.
The CBI court convicted Mishra, RJD Supremo Lalu Prasad and 43 others in a fodder scam case.