We describe a case of a patient referred by his orthodontist to our oral and maxillofacial surgery department, who presented with a chief complaint of protruded lower jaw deformity complicated by a medical history of type II diabetes. His skeletal deformity is diagnosed as class III skeletal malocclusion, related to retrognathic maxilla and mandibular hyperplasia. In this case report, we will mainly discuss the perioperative management of the patient’s diabetic condition in preparation for bimaxillary orthognathic surgery under general anaesthesia, byusing the insulin–glucose–potassium regimen.