UFC's Uriah Hall Says He Suffered 'Slight Heart Attack, Mini-Seizure'

UFC fighter Uriah Hall says he suffered a "slight heart attack" and "mini-seizure" the day before his fight with Vitor Belfort at UFC Fight Night: St Louis ... and doctors told him he's lucky to be alive.

"The doctor even said that even if I had made weight I probably would have died the next day because my body just wasn’t having it," Uriah said in an Instagram Live video.

Hall says his health scares were due to an injury that hindered his weight cut ... and he's refuting Dana White's claim that he was partying in L.A. -- insisting he was taking his training 100% serious.

The day before the event, the former 'TUF' finalist fainted on his way to the scale and was transported to a local hospital.