The 25-year-old suffered defeat against Dale Evans in a St Andrews Sporting Club fight at Glasgow's Radisson Blu Hotel on Thursday and was rushed to hospital after the match.
His girlfriend Chloe Ross said on Facebook:
"I'm absolutely heartbroken to say my annoying best friend passed away tonight at 11.02 very peacefully.
"Michael had severe bleeding and swelling to his brain.
"He had been complaining of headaches for the last few weeks but we put it down to migraines with the stress of his fight.
"Once he was taken off of his life support he managed 12 hours, 12 whole rounds off his life support, he fought right to the end and he's done us all so proud... He left doing the thing he's best at... there's only one.
"It has been the longest 24 hours of our lives. My baby has lost his daddy. But he will be so so proud of his dad in what he achieved."