Johnson, who had been isolating in Downing Street after testing positive for the virus last month, was taken to hospital on Sunday night because he still had a high temperature and his doctors felt he needed additional tests.
The prime minister is doing well and will undergo routine tests on Monday but will continue to lead the government, Housing Secretary Robert Jenrick said.
“He’ll stay in hospital as long as he needs to do that, but I’ve heard that he’s doing well and I very much look forward to him being back in Number 10 as soon as possible,” Jenrick said.
“This isn’t an emergency admission and so I certainly expect that he’ll be back at Number 10 shortly,” said, though he gave no time frame.
On March 27, Johnson became the first leader of a major power to announce that he had tested positive. The 55-year-old went into isolation at an apartment in Downing Street and said on Friday he was staying there as he still had a high temperature.