The 47-year-old is currently resting up at his home in Arizona after having surgery on January 24 to repair a hole in his heart.
While recovering, the singer's blood pressure suddenly dropped but a doctor found out the cause of the problem and he is now fine.
It was found that the drop in blood pressure was not down to the surgery but could have been a result of his diabetes.
Interventional cardiologist Dr. Mansour Assar said: 'Bret suffered no setbacks and is fine. It's always good for patients to be evaluated when they're not feeling well.'