Prehospital care providers frequently encounter patients with altered mental status (AMS). One of the more difficult aspects of managing these patients is assessing the extensive differential etiology of the symptoms. AMS can broadly be separated into traumatic and non-traumatic causes, with non-traumatic causes being the focus of this chapter. Prehospital endotracheal intubation has been performed in the United States for over 30 years, but has been the source of considerable debate for the past 10 years. This is primarily due to the large variance of reported success rates in multiple studies of both adult and pediatric patients and the negative outcome associated with the inability to successfully intubate the patient in the field. Hypoglycemia is a common cause of AMS in the prehospital setting, justifying the need for obtaining a blood glucose level on any patient who presents as altered.