For diabetics "there are extra precautions and sometimes complications," bandmate Pete Evick wrote Monday in an explanation of recent events that resulted in the rescheduling of some shows.
"The pain that led to the original surgery was so great that he simply could not perform last Thursday," he said.
Michaels was diagnosed with Type 1 diabetes as a child.
The pain started during an Oct. 25 show in Illinois, Evick wrote, but Michaels kept pushing through it and performing, sometimes against doctors' advice, in the days that followed. Two stents were inserted in his body ahead a performance before a University of Memphis Tigers football game on Halloween, but the show went on, Evick said.
Michaels landed in the hospital again immediately after that tailgate gig, but rallied for a concert in Knoxville, Tenn., on Nov. 1. That put him over the edge, Evick said.
"During the show he gave 100 percent, but he hurt himself. Jumping around with two stents was a bad idea," the guitarist wrote. "I can't explain the amount of blood or where it came from, but it was horrifying on his bus after the show."
Michaels had to postpone a charity performance last Thursday in Champaign, Ill., but was back on stage for a benefit concert in Las Vegas on Friday night.
"Keep in mind," Evick wrote, "when his appendix was bursting a few years ago, our intro music was rolling and no matter what I or anyone said to him, he was going on that stage. So imagine the pain he was in Thursday that kept him from performing."
The guitarist posted a picture he'd taken of Michaels lying in a hospital bed and flashing the peace sign, as well as a shot of one of the stents.
The former Poison lead singer has in recent years overcome several major health setbacks.
Michaels notably toughed it out to appear in late May 2010 on the live finale of
More recently, Michaels was forced to cut short a concert in New Hampshire in May because he was suffering from "extremely low" blood sugar.
The rocker's next show is scheduled for Thursday in Jacksonville, Fla.