Prison staff allegedly refused to take Pollard, 57, to the hospital for treatment of extreme pain until a congressman intervened in the situation, The Jerusalem Post reported.
Pollard's wife, Esther, has said in the past that the man's health is deteriorating and he has been hospitalized several times in recent years for severe pain.
Ashkenazi Chief Rabbi Yonah Metzger called on Jews around the world to keep Pollard in their prayers during Passover, which begins Friday evening.
Pollard is currently serving a life sentence he was given more than 26 years ago for handing over classified information about the United States to an ally in Israel.
Israeli President Shimon Peres said Tuesday he is working to get Pollard released.
"As president, I see it as very important to work determinedly to bring about Jonathan Pollard's release," Peres said.
"We are all united in the call to release him immediately. In all my meetings with President [Barack] Obama and top American government leaders I raised the request to release Pollard and I will continue to do so when I meet with Obama in June. My office is in touch with the campaign for Pollard's release and we will work hand in hand in any way possible to bring Jonathan Pollard home," he said.