The former Who Wants To Be A Millionaire? host suf-fered a minor stroke on a Bangok to London flight on March 1, and was taken to London's Charing Cross Hospital after landing.
He told a Sunday newspaper that it was the "most terrifying moment of my life" and he tried to call partner Jane Bird to tell her he loved her.
"I got very panicky. I was very alone up there, thinking, 'I could die'," he said. "I wasn't sure if I was going to fade away completely on my own.
"I am incredibly lucky to be alive because one in three people who have strokes don't make it. It has made me appreciate my life so much more."
Tarrant, 67, said he still has not regained full control of his movements or speech two months on, but he has been undergoing physiotherapy and has made changes to his lifestyle to minimise the risk of it happening again.
He had been filming in Asia and South America before collapsing at Heathrow after the long-haul flight, where a mystery cou-ple who had been on the plane called an ambulance.
He said doctors found a blood clot in his leg which caused the stroke.