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Glasgow Coma Scale (GCS)

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    Glasgow Coma Scale (GCS)

    Overview

    The Glasgow Coma Scale is a standardized clinical tool used to describe a person’s level of consciousness following an acute brain injury or other condition affecting responsiveness. It evaluates three independently assessed responses:

    • Eye opening
    • Verbal response
    • Motor response

    General Interpretation

    When the GCS is used to classify the initial severity of a traumatic brain injury:

    Total GCSGeneral TBI Severity Classification13–15Mild9–12Moderate3–8Severe

    These categories describe traumatic brain-injury severity and should not be used by themselves to diagnose the cause of altered consciousness, predict an individual patient’s outcome, or make treatment decisions. Clinical findings, changes over time, pupillary examination, vital signs, medications, imaging, and the overall clinical situation must also be considered.

    Recommended Assessment Approach

    1. Check for factors that may interfere with assessment.
    2. Observe spontaneous eye, verbal, and motor responses.
    3. Stimulate with an appropriate verbal request and, when clinically necessary, an appropriate physical stimulus.
    4. Rate the best observed response in each component.
    5. Document the individual eye, verbal, and motor findings and repeat the assessment to identify changes or trends.

    Standardized assessment, clinician training, and consistent documentation improve the reliability of GCS scoring.

    Not-Testable Responses

    A component should be documented as not testable (NT) when an underlying condition prevents a valid assessment. Examples may include:

    • Endotracheal intubation preventing verbal assessment
    • Severe swelling preventing eye opening
    • Sedation or neuromuscular blockade
    • Language or communication barriers
    • Facial, ocular, spinal-cord, or extremity injury affecting the response

    A response that cannot be tested should not automatically be assigned a score of 1 or 0. When any component is not testable, document the available components and the reason the component could not be assessed rather than relying on a potentially misleading total score.

    Important Limitations

    The GCS measures observable responsiveness; it does not identify the underlying cause of impaired consciousness. Scores may be affected by intoxication, sedating medications, paralysis, intubation, aphasia, hearing impairment, language differences, facial trauma, spinal-cord injury, and other clinical factors.

    Inter-rater reliability is generally acceptable when the assessment is standardized, but reliability varies among settings and assessors. Component-level documentation, appropriate training, and repeated assessments are therefore recommended.

    Pediatric Considerations

    The standard verbal and motor criteria may not be developmentally appropriate for infants or preverbal children. An age-appropriate Pediatric Glasgow Coma Scale should be used when applicable. Research supports its use in evaluating preverbal children with blunt head trauma, but results must still be interpreted with the child’s developmental level and overall clinical condition.

    Clinical Safety Statement

    The Glasgow Coma Scale is a clinical assessment and communication tool. It should not replace a complete neurologic examination, clinical judgment, emergency evaluation, or applicable trauma and head-injury protocols. A declining score or an unexplained reduction in consciousness requires prompt professional medical assessment.

    Evidence-Based References

    1. Teasdale G, Jennett B. Assessment of coma and impaired consciousness: a practical scale. Lancet. 1974;2(7872):81-84. doi:10.1016/S0140-6736(74)91639-0.
    2. Teasdale G, Murray G, Parker L, Jennett B. Adding up the Glasgow Coma Score. Acta Neurochir Suppl (Wien). 1979;28:13-16. PMID: 290137.
    3. Teasdale G, Maas AIR, Lecky F, Manley G, Stocchetti N, Murray G. The Glasgow Coma Scale at 40 years: standing the test of time. Lancet Neurol. 2014;13(8):844-854. doi:10.1016/S1474-4422(14)70120-6.
    4. Reith FCM, Van den Brande R, Synnot A, Gruen R, Maas AIR. The reliability of the Glasgow Coma Scale: a systematic review. Intensive Care Med. 2016;42(1):3-15. doi:10.1007/s00134-015-4124-3.
    5. Reith FCM, Lingsma HF, Gabbe BJ, Lecky FE, Roberts I, Maas AIR. Differential effects of the Glasgow Coma Scale Score and its components: an analysis of 54,069 patients with traumatic brain injury. Injury. 2017;48(9):1932-1943. doi:10.1016/j.injury.2017.05.038.
    6. Borgialli DA, Mahajan P, Hoyle JD Jr, et al; Pediatric Emergency Care Applied Research Network. Performance of the Pediatric Glasgow Coma Scale Score in the evaluation of children with blunt head trauma. Acad Emerg Med. 2016;23(8):878-884. doi:10.1111/acem.13014.
    7. National Institute for Health and Care Excellence. Head Injury: Assessment and Early Management. NICE Guideline NG232. Published May 18, 2023.
    8. University of Glasgow. Glasgow Coma Scale: structured approach to assessment and documentation. Accessed July 12, 2026.


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