A person in a coma is completely unconscious, cannot be woken up, and does not respond meaningfully to voice, touch, or pain. Unlike deep sleep, where someone can be roused with enough stimulation, a coma represents a fundamental shutdown of the brain’s normal wakefulness systems. If you’re trying to figure out whether someone is truly in a coma or just deeply unresponsive, there are specific signs that medical professionals look for, and some you can observe yourself.
What a Coma Looks Like
The most defining feature of a coma is the complete absence of purposeful response. A person in a coma will not open their eyes, speak, or follow instructions. They won’t reach for your hand, turn toward your voice, or show any sign of awareness. Their eyes stay closed. They may breathe on their own or may need a ventilator, depending on the severity and cause.
This is different from someone who is simply unconscious for a brief moment, like during a fainting spell. A coma persists. The person cannot be woken by shaking, shouting, or any other external stimulus. Even strong physical stimulation, like firm pressure on a fingernail bed or the ridge above the eye, produces no purposeful movement. There may be reflexive responses, like limbs pulling away or extending stiffly, but these are automatic brainstem reactions rather than signs of awareness.
How Doctors Assess Responsiveness
In a hospital, medical teams use a standardized tool called the Glasgow Coma Scale (GCS) to measure how deeply unconscious someone is. It scores three things: whether the eyes open, whether the person makes any sounds, and whether the body moves in response to stimulation. Each category is scored from 1 (no response at all) up to a maximum of 4 for eye opening, 5 for verbal response, and 6 for motor response. The total ranges from 3 to 15.
A score of 8 or below is classified as severe brain injury and typically indicates a coma. At a score of 3, the person shows absolutely no eye opening, no sounds, and no movement. As scores increase, you might see eyes opening to pain (but not spontaneously), incomprehensible groaning rather than words, or reflexive body movements that aren’t purposeful. A score of 13 to 15 is considered mild impairment, meaning the person is conscious and responding, even if confused.
Doctors also test brainstem reflexes to gauge how deep the coma is. They shine a light into each eye to see if the pupil constricts. In a healthy brain, the pupil shrinks quickly. In a deep coma, one or both pupils may be fixed and unresponsive. They’ll gently touch the surface of the eye with a wisp of moistened cotton to check for a blink reflex. They test the gag and cough reflexes as well. When these brainstem reflexes start disappearing, it signals increasingly severe brain dysfunction.
What Causes a Coma
Comas happen when something disrupts the brain’s ability to maintain consciousness, either by damaging the brainstem directly or by affecting both hemispheres of the brain at once. The most common causes include traumatic brain injuries from car accidents or violence, strokes that cut off blood supply to critical brain areas, and drug or alcohol overdoses that suppress brain activity to dangerous levels.
Medical conditions can also trigger a coma. Severely high or low blood sugar in diabetes is one well-known cause. Infections like meningitis or encephalitis create swelling around the brain that can push consciousness offline. Lack of oxygen after near-drowning, cardiac arrest, or carbon monoxide exposure damages brain tissue rapidly. Prolonged seizures lasting more than five minutes, brain tumors pressing on the brainstem, and conditions like dangerously low sodium levels or severe sepsis can all lead to coma as well.
Coma vs. Sleep vs. Other States
Sleep and coma look superficially similar, but they are fundamentally different. During sleep, the brain cycles through organized electrical patterns and can be interrupted at any time by a loud noise or physical nudge. In a coma, those organized patterns break down. An EEG (a test that records brain electrical activity) in a comatose patient shows abnormal, disorganized waves rather than the structured rhythms of normal sleep. When normal sleep features are preserved on an EEG, it’s actually considered a more favorable sign for recovery.
There are also states that look like a coma but aren’t. In a vegetative state, the person’s eyes may open and close, and they may have sleep-wake cycles, but they show no signs of awareness. They’re “awake” in the most basic sense but not conscious. Remarkably, brain imaging research has shown that some patients diagnosed as vegetative may actually retain awareness. When asked to imagine playing tennis, one such patient showed the same pattern of brain activity as a healthy person performing the same mental task, despite appearing completely unresponsive.
A minimally conscious state is a step above vegetative: the person shows inconsistent but real signs of awareness, like occasionally following a simple command or tracking an object with their eyes. Brain death, on the other hand, sits at the opposite end. It means all brainstem function has permanently ceased, including the ability to breathe independently. Brain death is irreversible and is legally considered death.
What Happens at the Hospital
When someone arrives unresponsive, the medical team works simultaneously to stabilize the body and identify the cause. A CT scan of the head is typically the first imaging step. It can quickly reveal bleeding, swelling, masses, or signs that brain tissue is being pushed out of position, a dangerous process called herniation. The degree to which the brain’s hemispheres have shifted sideways is closely tied to how impaired consciousness is.
If the CT doesn’t explain the coma, an MRI provides more detailed images of brain structure, including early signs of tissue damage from reduced blood flow. Blood tests check for metabolic causes like extreme blood sugar levels, toxins, drug levels, infections, and electrolyte imbalances. An EEG may be used to detect seizure activity that isn’t visible from the outside.
Signs of Waking Up
Recovery from a coma, when it happens, is rarely a sudden “waking up” moment like you see in movies. It’s a gradual, often messy process that can take days to months. The earliest sign is typically a localized response: the person begins reacting inconsistently but specifically to things around them, like turning toward a sound or pulling away from something uncomfortable in a way that seems intentional rather than reflexive.
From there, patients often enter a confused and agitated phase. They may thrash, cry out, or behave in ways that seem bizarre and unpurposeful. This is actually a sign of progress, even though it looks alarming. As recovery continues, the person starts following simple commands more consistently, though they remain confused and may say things that don’t make sense. Purposeful responses to simple instructions, like “squeeze my hand” or “look at me,” are some of the clearest early markers that consciousness is returning.
For patients who entered a vegetative state after the coma, regaining consciousness is most likely within the first six months. After a full year in a vegetative state, meaningful recovery becomes rare, though not impossible.
If You Find Someone Unresponsive
If you encounter someone who won’t wake up, the first priority is checking whether they’re breathing. Try calling their name loudly and tapping their shoulders firmly. If they don’t respond at all, look at their chest for signs of normal breathing. If they’re not breathing normally, begin CPR and call emergency services immediately. If they are breathing but completely unresponsive, roll them onto their side into a recovery position to keep their airway clear, and call for help. Do not try to give them food, water, or medication. The cause of their unresponsiveness could range from a drug overdose to a stroke to a diabetic emergency, and professional assessment is needed to determine what’s happening inside the brain.