Emergency services were called to the great train robber's nursing home in north London.
Emergency services were called to the 81-year-old's nursing home in Barnet, north London, after he fell ill.
His son, Michael, said he was conscious and preparing to undergo a CT scan as part of a battery of tests to find out what happened.
Speaking from Barnet General Hospital, Mr Biggs said: "He has been taken into hospital. We do not know if it is a suspected stroke or what it is.
"They are going to do a CT scan. I am here now. He is conscious at the moment. The CT scan will find out whether it is to do with an infection or another stroke.
"They are going to have to check."
Mr Biggs has suffered declining health since being transferred from prison to a care home in Bells Hill on medical grounds last year.
He first suffered a stroke in 1998 and has been admitted to hospital several times since returning to Britain in 2001.
Speaking in December, his son said he was "very ill" and could die "at any moment" and could only communicate through a word board.
Originally from Lambeth, south London, he was a member of a gang that made off with £2.6 million from a Glasgow to London mail train in 1963.
Biggs was given a 30-year sentence but escaped from Wandsworth prison, south London, in a furniture van after spending 15 months in jail.
He was on the run for more than 30 years, living in Spain, Australia and Brazil before returning to the UK voluntarily.