Comedian Eddie Izzard has been ordered to rest during his attempt to complete 27 marathons in 27 days in South Africa.
The charity run - one for each year former South African president Nelson Mandela was imprisoned - is for Sport Relief.
Mr Izzard, who completed 43 marathons in 51 days in 2009 for the same charity, has completed four of the 26-mile runs in four days this time round.
According to a BBC spokesman, Mr Izzard visited a hospital in the country following medical advice.
"Eddie is in good spirits and is looking forward to continuing his marathon of marathons," said Damian Kavanagh, controller of BBC Three.
"Eddie is determined to complete the challenge and we will be with him every step of the way on BBC Three."
The part-time actor is raising money for his latest venture, titled Eddie Izzard: Marathon Man, which will help Sport Relief support disadvantaged people in the UK and across the world.