His lawyer, Badie Arif Ezzat, told the newspaper "Al-Hayat Arab" that Aziz is in great pain and may not have long to live.
Ezzat did not say when Aziz, who is 69 years old, was struck by illness.
Aziz is in custody and faces charges for murders allegedly committed during the regime of Saddam Hussein. He says he is innocent.
Saddam Hussein In Pictures
A slideshow of photographs from Saddam Hussein's years ruling Iraq through his downfall.