The Glasgow Coma Scale (GCS) is a standard tool for rapid assessment of level of consciousness, developed by G. Teasdale and B. Jennett (Lancet, 1974) at the Institute of Neurological Sciences in Glasgow for patients with traumatic brain injury. Over five decades the scale has become universal: it is used in TBI, stroke, poisoning, metabolic encephalopathies, and recovery from anesthesia.
Assessment is based on three independent components: eye opening (E, 1–4), verbal response (V, 1–5), and motor response (M, 1–6). The total ranges from 3 to 15. It is essential to document not only the total but each component separately (E3V4M5 = 12), because prognosis and management depend heavily on which component is impaired.
Standard TBI stratification: 13–15 — mild, 9–12 — moderate, ≤8 — severe (an indication for intubation and mechanical ventilation in the absence of other causes of decreased consciousness). The trend in the score matters more than the absolute value: a drop of 2 points or more warrants urgent neuroimaging and neurosurgical consultation.
When to use
Any traumatic brain injury from the initial assessment onward (EMS, emergency department, ICU).
Acute stroke, for severity stratification and decisions on thrombolysis/thrombectomy.
Poisoning (alcohol, opioids, benzodiazepines) — assessing depth of CNS depression and need for mechanical ventilation.
Post-anesthesia recovery — monitoring return of consciousness.
Motor response (M, 1–6): 6 — obeys commands; 5 — localizes pain (purposefully moves hand toward the stimulus); 4 — withdraws (flexion); 3 — abnormal flexion (decorticate posturing); 2 — abnormal extension (decerebrate posturing); 1 — no response. The best response from either side is scored.
Clinical example
Case
A 34-year-old man is brought in after a motor vehicle collision. He was unconscious at the scene for about 5 minutes. On examination: opens eyes only to pain (E2), utters incomprehensible words without structure (V3), flexes the arm with some withdrawal to a painful stimulus at the nail bed (M4). BP 130/80, HR 92, SpO2 96%.
Calculation
E2 + V3 + M4 = 9 points (documented as E2V3M4).
Interpretation and management
Moderate TBI, at the upper boundary of severe. Emergency head CT and neurosurgical consultation are indicated. Continue ABC management, monitor GCS every 15 minutes. Be prepared for intubation if the score falls further (GCS ≤8). In parallel, assess pupils and focal neurologic signs, and rule out other causes (hypoglycemia, poisoning).
Limitations and cautions
Not applicable for the V component in intubated patients — document as "V1t" or use the FOUR Score instead.
Eyelid edema or facial/orbital injury makes the E component impossible to assess.
Under sedation, neuromuscular blockade, or alcohol intoxication, the scale does not reflect true neurologic status.
In children under 5 years, the Pediatric Glasgow Coma Scale is used, with an adapted V component.
Aphasia after stroke artificially lowers V — rely on the trend in motor response and neurologic examination.
Each component has a minimum of 1 point (no response), not 0. So "completely absent consciousness" = 1 + 1 + 1 = 3. A score below 3 is not possible.
What is recorded for an intubated patient?
Documented as E?V1tM? — the "t" indicates intubation. Many protocols recommend switching to the FOUR Score (Full Outline of UnResponsiveness), which does not include a verbal component.
How often should GCS be assessed?
In an unstable patient — every 15 minutes for the first 2 hours, then hourly. After stabilization — every 4 hours. Any drop of 2 points or more requires immediate reassessment and CT.
Is GCS = 8 an automatic indication for intubation?
This is the classic rule of thumb, but the decision is made clinically: consider the trend (stable vs deteriorating), preservation of protective airway reflexes, and oxygenation.
Where is the motor response scored?
The best response from all limbs is documented. However, in cases of asymmetry, lateralization must be noted separately (e.g., "M5 right, M3 left").
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Aleksandr A. Aulov
Physician, internal medicine, Sechenov School — independent medical education platform.
Calculators are compiled from the original publications and current clinical guidelines. Interpretation thresholds follow the source study unless stated otherwise.
This calculator is intended for healthcare professionals. Do not use it for self-diagnosis or self-treatment. Management decisions are made by the treating clinician based on the full clinical picture of the individual patient.
Last clinical review: April 28, 2026 ·
Author: Aleksandr A. Aulov,
MD, internal medicine ·
Primary source: Teasdale G, Jennett B. Lancet 1974; 2(7872): 81-84