"The prime minister’s condition is stable and he remains in intensive care for close monitoring. He is in good spirits", Downing Street said in a statement.
The 55-year-old was admitted to the hospital on Sunday with persistent symptoms of the COVID-19 coronavirus disease and transferred to intensive care on Monday.
Foreign Secretary Dominic Raab, who is deputising for him, said earlier that the prime minister was receiving standard oxygen treatment and breathing without assistance.
"I’m confident he’ll pull through... He is a fighter and he’ll be back at the helm leading us through this crisis in short order", he told reporters at a coronavirus briefing.
So far, the UK has 55,242 confirmed coronavirus cases. So far, 213,181 people have been tested in Britain and 6,159 patients have died from virus-related complications.