A normal Glasgow Coma Scale (GCS) score is 15, which means a person is fully awake, aware, and responsive. The scale runs from 3 to 15, with 3 being the lowest possible score (deep coma or death) and 15 representing completely normal brain function. There is no score of zero.
How the Score Is Calculated
The GCS measures three things: whether your eyes open, whether you can speak, and whether you can move purposefully. Each category is scored separately, and the numbers are added together for a total.
Eye opening (1 to 4 points):
- 4: Eyes open on their own, without any prompting
- 3: Eyes open in response to sound or voice
- 2: Eyes open only when pressure is applied
- 1: Eyes don’t open at all
Verbal response (1 to 5 points):
- 5: Speaks clearly, knows who and where they are
- 4: Speaks but seems confused
- 3: Uses words, but they don’t make sense in context
- 2: Makes sounds but no recognizable words
- 1: No verbal response at all
Motor response (1 to 6 points):
- 6: Follows instructions to move on command
- 5: Reaches toward and pushes away something pressing on them
- 4: Pulls away from pressure as a reflex only
- 3: Muscles flex inward in response to pressure
- 2: Muscles extend outward in response to pressure
- 1: No movement at all
A normal score of 15 means: eyes open spontaneously (4) + oriented speech (5) + follows commands (6). Any score below 15 signals some degree of impaired consciousness.
What Different Score Ranges Mean
GCS scores are grouped into three severity levels, most commonly used to classify traumatic brain injuries:
- 13 to 15: Mild. The person is largely awake and aware, though they may be slightly confused or slow to respond. A score of 15 is completely normal. Scores of 13 or 14 suggest a mild impairment, like a concussion.
- 9 to 12: Moderate. The person has significant difficulty communicating or following commands, and their eyes may not open without stimulation.
- 3 to 8: Severe. The person is in a coma or near-coma state, with little to no purposeful response.
The link between GCS score and survival is strong. In one 10-year study of penetrating brain injuries, mortality was about 4% in the mild range, 22% in the moderate range, and 87% in the severe range. A GCS of 3, the absolute lowest score, carries the worst prognosis of all, with outcomes so distinct that researchers sometimes separate it from the rest of the “severe” category.
How the Scale Works for Children
The standard verbal scale doesn’t work for babies and very young children who can’t talk yet. A modified version adjusts the verbal category to match what’s developmentally normal. For infants, the top verbal score (5 points) is given for cooing and babbling. A score of 4 means irritable crying, 3 means crying only in response to pain, 2 means moaning, and 1 means silence. For older children who can use words, the scale more closely mirrors the adult version. In preverbal or very young children, the motor response becomes the most important part of the assessment.
When a Full Score Isn’t Possible
Some situations make it impossible to score all three categories. A patient on a breathing tube can’t speak, so no verbal score can be recorded. In these cases, the eye and motor scores are added together and followed by a “T” (for tube). This modified score ranges from 2T to 10T. Similarly, if someone’s eyes are swollen shut from injury, the eye-opening score can’t be assessed reliably. These limitations are important context: a score that looks low on paper may partly reflect the inability to test rather than true brain impairment.
The GCS-P: Adding Pupil Response
A newer version of the scale, called the GCS-P, factors in whether the pupils react to light. This gives a more complete picture of brain function, especially in severe injuries. It works by subtracting a Pupil Reactivity Score from the standard GCS total. If both pupils react normally, nothing is subtracted. If one pupil is unresponsive to light, 1 point is subtracted. If neither pupil reacts, 2 points come off. The GCS-P ranges from 1 to 15, with 15 still representing normal function. This expanded score is used alongside the standard GCS, not as a replacement for it.
What a Score of 15 Actually Tells You
A GCS of 15 confirms that someone is conscious and alert, but it doesn’t rule out brain injury entirely. A person can score a perfect 15 and still have a concussion, a small brain bleed, or other neurological problems that require further evaluation with imaging or cognitive testing. The GCS is a rapid screening tool designed to measure consciousness in the moment. It’s especially useful for tracking changes over time: a score that drops from 15 to 12 over a few hours is a red flag, even though 12 might not sound dramatically low on its own. The trend matters as much as the number.