"While the surgery went well and doctors are optimistic that the rocker will make a full recovery, the fact that he was exhausted due to his rigorous schedule prior to the surgery and coupled with the fact that he has diabetes, the surgery has taken its toll," his rep tells PEOPLE in a statement.
The location of the facility specializing in the rehabilitation of diabetic patients wasn't disclosed.
Michaels had been scheduled to perform in San Antonio on Sunday night. He had been suffering severe stomach pains all day and was urged to seek medical treatment.