Yosef collapsed during Saturday prayers and was transported to Hadassah Medical Center, where he was described as conscious. He will probably remain for the next few days, the report said.
Yosef's illness comes at a potentially important time for Shas. The Jerusalem Post said a poll this week predicted Shas would win as many as 10 seats in the Jan. 22 parliamentary election.
Yosef has been in and out of hospitals in recent years and has undergone three angioplasty procedures, Ynet news said. The most recent surgery was in 2006.