One prisoner has not eaten in 74 days while another has gone 114 days without food, the Palestinian news agency Ma'an reported.
Fares Ziad, a lawyer for Addameer, said Wednesday that he found the prisoners -- Hassan Safadi, Samer al Barq and Ayman Sharawna -- suffering from various physical problems when he visited the clinic at Ramle prison on Tuesday.
Safadi, who has not eaten for 71 days, is experiencing a number of ailments, including liver problems, low blood pressure and chronic joint pain, Addameer said in a statement.
Ziad said Safadi was not able to drink water on Monday because it now causes his hands and feet to swell.
Sharawna has lost about 80 percent of the vision in his right eye, the lawyer said, and has lost feeling in his left leg.
He has not eaten for 74 days. For the last 10 days, Sharawna has vomited blood as well as water.
Ziad said he was unable to meet with al Barq, who was on the 114th day of a hunger strike and permanently confined to bed because he is unable to walk.
Israel is holding all three men without charge or trial. They are among 250 people being held in administrative detention.