The 51-year-old musician and his band performed three songs in Manchester, N.H. before he fled the stage and was rushed to paramedics. Michaels has Type 1 diabetes, and the cause of the emergency was "extremely low" blood sugar levels.
"In the 9 years I've stood next to him, I've never seen a look like the one on his face as if I was a complete stranger," guitarist Pete Evick writes on the musician's Facebook page. "He returned to the stage only to announce that he could not continue."
"As you all know he is a health fanatic and fiercely monitors his blood sugar," he continues. "He basically had to be dragged off the stage in his sickest of conditions. When I rushed to the bus he could barely speak, but begged me to apologize to the fans and seemed only concerned with them."
Michaels and his band are scheduled to perform Friday night in Wilkes-Barre, Pa.
Notable deaths of 2014 [PHOTOS]