Dave Allen is set to retire from boxing after his defeat by David Price.
The heavyweight was pulled out by his corner following the 10th round of the one-sided contested.
Allen was given oxygen but then collapsed as he tried to stand up from his stool.
He was taken to hospital where he underwent tests and initially reassured fans by posting a picture of himself giving the thumbs up.
But he later admitted his health has been deteriorating over the last year and will likely hang up his gloves.
Allen tweeted: "Don't want anyone to worry about me, just a hard man gone old and soft the last 18 months.
"I'm very happy and proud of David Price; I will be okay but the last 12 months or so my health has been deteriorating and I’m glad I hung on, took the chance and made money and now probably done."
Allen was riding the crest of a wave after stopping Lucas Browne earlier this year.
He was the favourite to beat Price but was dominated by the imposing Liverpudlian throughtout.
