The attorney for Khaled Dumeisi says the 61-year-old has a history of heart trouble and blood clots.
Attorney James Fennerty says Dumeisi was taken to Rush Presbyterian St. Luke's Medical Center on Friday night.
Federal prosecutors contend Dumeisi was paid to spy on Iraqi opposition leaders in this country.
He is charged with serving as the agent of a foreign government without registering, lying to an immigration official and lying to a federal grand jury.
He had been held in the federal government's Metropolitan Correctional Center since his arrest on July 9.
Viewers with disabilities can get assistance accessing this station's FCC Public Inspection File by contacting the station with the information listed below. Questions or concerns relating to the accessibility of the FCC's online public file system should be directed to the FCC at 888-225-5322, 888-835-5322 (TTY), or firstname.lastname@example.org.