Benjamin Netanyahu has been rushed to hospital for tests following an illness.
Israel's prime minister "is suffering from a high fever and is coughing," a spokesman for the 68-year-old said.
He was taken to a hospital in Jerusalem.
Mr Netanyahu's personal physician believes he had not fully recovered from an illness two weeks ago, the spokesman said.
Dr Tzvi Berkowitz thought his symptoms had worsened as a result.
He therefore decided Mr Netanyahu should undergo further tests at hospital.
Mr Netanyahu is likely to be released on Tuesday night after doctors found he was suffering from a mild respiratory illness.
"The prime minister has completed a series of tests and will be released home tonight," a statement from his office said.
"The tests showed a mild viral illness in the upper respiratory tract."
It comes after the prime minister was questioned by Israeli police over his alleged dealings with the country's largest telecommunications company — one of three cases weighing on his political future.
It was the second time Mr Netanyahu had been questioned in the investigation into allegations he awarded regulatory favours to Bezeq Telecom Israel in return for favourable coverage on a news site the company's owner ownes.
Both Mr Netanyahu and Bezeq have denied wrongdoing.
So far, partners in his governing coalition have stood by him, saying they are awaiting the attorney general's next moves.
Surveys have shown about half of Israelis believe the police over the prime minister and think he should step down, while a third think he should remain in office.
Support for Mr Netanyahu's Likud party remains strong in opinion polls.
