Jamshid Dehghan, Kamal Malaii and Hamed Ahmadi were all transferred to the prison’s clinic after going into a coma on January 4.
They were returned to their cells after regaining consciousness, before Mr Dehghan lost consciousness for a second time.
The three are among six prisoners who have refused food for more than two months at the prison.
The six Sunni political prisoners went on hunger strike from November 4 and are still demanding a revised trial in public and their return to their previous prison ward in Rajaii-Shahr prison in Karaj.
Despite requests from human rights organizations to break their strike, the political prisoners emphasized on its continuation as the only means to make their voices heard.
Meanwhile Report from Political prisoner Zaniyar Moradi, who is on death row at the prison say that he is currently being deprived of medical treatment for infection of the vertebrae resulting from torture.
Prison chiefs have said there is no budget dedicated to medical care for prisoners sentenced to death.
The doctors have said that they will face death continuing with their hunger strike.