Neurology
Glasgow Coma Scale (GCS)
Level of consciousness from eye, verbal and motor response.
Education and reference only. Not a substitute for clinical judgement, local policy or product labelling. Always verify before clinical use. Values are calculated in your browser and never stored.
Background
The Glasgow Coma Scale (GCS) is the universal tool for describing level of consciousness, scoring three components: eye opening (1–4), verbal response (1–5) and motor response (1–6). The total ranges from 3 (deeply unconscious) to 15 (fully alert and oriented). It was devised by Teasdale and Jennett to give a reproducible, communicable language for conscious level in head injury and acute illness, and to track change over time. The best response in each category is recorded.
Interpreting the result
By convention a total of 13–15 is mild impairment, 9–12 moderate, and 8 or below severe. A GCS of 8 or less indicates a high risk to the airway and usually prompts urgent senior and anaesthetic input for airway protection. The total is useful, but the three component scores carry more clinical information and a falling motor score is particularly concerning, so the components should always be reported.
Advice
GCS ≤8 indicates a high risk to the airway and usually prompts urgent senior/anaesthetic input. Always report the three components, not just the total.
Worked example
A head-injured patient opens their eyes to speech (3), is confused (4) and localises to pain (5): E3 V4 M5 = GCS 12. This is a moderate impairment of consciousness that warrants close monitoring for any further decline.
Pearls / pitfalls
- Always document the three components (e.g. E3 V4 M5), not only the total — the same total can reflect very different clinical pictures.
- A GCS of 8 or less signals airway risk and usually prompts urgent senior/anaesthetic assessment for airway protection.
- Intubation, sedation, language barriers, intoxication or dysphasia can confound the verbal score; record the reason a component cannot be assessed.
- A falling motor score is an especially important sign of deterioration and should trigger reassessment.
Evidence & validation
Described by Teasdale and Jennett in 1974 and validated extensively since, the GCS underpins trauma scoring and is embedded in UK head-injury guidance (NICE) and Advanced Trauma Life Support teaching.
Frequently asked questions
What is the lowest possible GCS?
The minimum total is 3 (one point each for eye, verbal and motor), which indicates a deeply unconscious patient. The maximum is 15.
Why does a GCS of 8 matter?
A GCS of 8 or less indicates a high risk of losing airway protection. It usually prompts urgent senior and anaesthetic review to consider securing the airway.
Should I report the total or the components?
Both, but the three components are more informative. Two patients can share a total yet have very different patterns, so always record eye, verbal and motor scores.
What if a component cannot be assessed?
If a patient is intubated, sedated or unable to speak, record that the component is not testable and the reason, rather than guessing a value.
Does a single GCS reading tell the whole story?
No. Trend matters as much as the absolute value; a falling score, especially in the motor component, signals deterioration and should prompt urgent reassessment.
References
- Teasdale G, Jennett B. Assessment of coma and impaired consciousness: a practical scale. Lancet. 1974;304(7872):81–84.
- NICE NG232: Head injury: assessment and early management. 2023.
About the creator
Teasdale & Jennett
Related calculators
Need a calculator we don't have — or a custom tool?
We build evidence-led clinical calculators, dashboards and reference tools for teams.