The Glasgow coma scale (GCS) is a tool used to assess and calculate a patient’s level of consciousness. It was developed more than 40 years ago by two neurosurgeons in Glasgow and is widely applied today.1 The GCS uses a triple criteria scoring system: best eye opening (maximum 4 points), best verbal response (maximum 5 points), and best motor response (maximum 6 points). These scores are added together to provide a total score between 3 and 15 (fig 1). Fig 1 Glasgow coma scale. Score the best level of response seen for each component. Adapted from Teasdale G. Forty years on: updating the Glasgow Coma Scale. Nursing Times 2014;110:42;12-16 The GCS was initially used to assess level of consciousness in patients after head injury, but the scale is now used in many acutely unwell patients. In hospitals it is also used to monitor patients in intensive care units. During placements you may hear the GCS used to describe confused patients on care of the elderly wards, trauma patients in the emergency department, or patients seen by the “crash” medical emergency team. As a student, you might be asked to calculate the GCS score as part of the general or neurological examination of a patient, especially if the patient is confused, drowsy, or unresponsive. As you gain experience in calculating a GCS score in practice, you will become more confident and the score will become more accurate. Assessment of a GCS score can be deemed subjective, so it is best practice that two independent clinicians calculate a GCS score to mitigate subjective bias. Clinically, the GCS may help streamline trauma services through major trauma bypass protocols. In parts of the United Kingdom patients with a GCS score of 13 or less can be transported directly by ambulance to specialist major …