Ronaghi Maleki has been on hunger strike since more than a week ago to protest his detention conditions.
The 26-year-old blogger has said that he will refuse to eat food until he is granted medical leave.
Amnesty International said last week Ronaghi Maleki had developed kidney disease since his arrest.
According to the rights group, Ronaghi Maleki has undergone at least four operations and now requires another to remove his left kidney.
Ronaghi Maleki was jailed following the 2009 antigovernment protests and sentenced to 15 years in prison on charges that included insulting Iran's leaders and spreading propaganda against the Islamic establishment.
Ronaghi Maleki has been reportedly subjected to psychological and physical torture in prison.