Charlie Webster said she was ready to die while fighting a rare form of malaria that left her in a coma on a life-support machine.
The TV presenter said that one doctor told her "you are dying" as she clung to life in a Rio hospital.
She recalled shouting "no, no, no" aloud after deciding to fight to recover, having promised her mother she would come back from the trip alive.
The sports host also told the Sun that she hallucinated a bizarre conversation with the figure of death who told her: "Come on, you've got to go."
Webster fell ill after contracting malaria during a 3,000 charity bike ride on the way to Brazil, where she was due to cover the Rio Olympics.
As her condition deteriorated, one medic told her: "We need you to know that you are dying. Get hold of your family."
The sports host said there were no words to describe the pain she was in, while medics struggled to work out what was causing her illness.
She has since recovered enough to fly back to London, but remains in a serious condition.
Webster said she had got injections against illness before setting off on the charity bike ride, but was told she did not need one for malaria.
She aims to return to presenting by the end of the year.