In prehospital acute care, an undefined disturbance of consciousness frequently occurs as an alarm diagnosis for rescue vehicles. This group of patients usually includes those affected by hyperglycemic emergencies; since in general practice such patients are often already identified in the subacute stage and can be admitted for inpatient treatment if necessary (e.g. by ambulance), an acute life-threatening hyperglycemic emergency rarely occurs. In acute care, however, in addition to ensuring vital functions—especially airway management in the case of impaired consciousness Glasgow Coma Scale (GCS) ≤ 8—the diagnostic differentiation from other acute clinical pictures, such as a central neurological deficit, is difficult, since most ambulances and physician-staffed emergency response vehicles do not have the diagnostic equipment for arterial blood gas (ABG) analysis or imaging. Especially the differentiation between ketoacidotic and hyperosmolar hyperglycemic emergency is difficult due to the lack of ABG; for causal therapy the patient is also referred to the clinical setting because insulin in its different dosage forms is also not part of the common drug equipment of rescue vehicles. This means that prehospital acute care is generally limited to rapid diagnosis, stabilization of vital functions (especially airway management, volume substitution), and transport to the nearest suitable hospital (with intensive care capacity if necessary). Nevertheless, development of the competence “clinical reasoning” is paramount because a successful clinical therapy course is already set preclinically.