Coma (Persistent Vegetative State)

A coma is a disruption in brain activity. It prevents consciousness, meaning you’re unconscious, unaware of the world around you and impossible to wake. Comas have varying levels of severity and can happen because of many different conditions. Some causes of comas are treatable or reversible. Comas are medical emergencies and need immediate care.


What is a coma?

Being in a coma means you’re unconscious, unaware and unresponsive to what’s happening around you. It also blocks your awareness of yourself, including your body’s status and anything your body needs. At the most basic level, a coma means your brain isn’t working as it should.

Comas are a possible complication of conditions that can severely disrupt or damage your brain. A coma is different from person to person. Comas have levels of severity, and some are deeper — meaning the severity of brain activity disruption is greater — than others.

A coma is a medical emergency. If you’re with someone who’s unconscious and unresponsive, call 911 (or your local emergency services number) immediately. Many causes of coma need immediate medical care, and any delay could lead to dangerous complications or death.

How common are comas?

The available research suggests that there are a little over 250 new comas per 100,000 people in the population of the United States and the United Kingdom each year. However, there’s uncertainty about the accuracy of that estimate. And there are multiple reasons for that uncertainty. One major reason is that some common causes of coma are treatable and quickly reversible by first responders, sometimes without the need for a hospital visit. Another reason is that many conditions look like comas but are actually something else.

Comas can affect anyone who has a medical condition that affects the way their brain functions. They can happen to people regardless of age, sex, race, ethnicity or other demographic factors.


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Symptoms and Causes

What are the symptoms of a coma?

There are three main symptoms of a coma:

  • Unconsciousness. This is like a very deep sleep, and it’s impossible to wake you up.
  • Lack of eye response. This means your eyes stay closed, and someone holding your eye open doesn’t cause you to react. Your eyes might have some reflex movements, such as reacting to light, blinking, or turning when your head is moved, but these reflexes might not happen as expected if your coma is very deep.
  • Lack of motor (movement) response. This means you don’t consciously move. You may still have some reflex responses, but not if your coma is very deep. The type of reflexes you show can also indicate how deep your coma is.

While the above symptoms usually happen with a coma, there can also be some variation. Some people may have different movement responses.

The Glasgow Coma Scale

The Glasgow Coma Scale (GCS) is the most widely used scale for grading how severe a coma is. The GCS has three main categories, and each category gets a score. A score of 15 is the highest possible, and it means you’re awake and aware of your surroundings. You can also understand and respond to questions and follow commands.

Generally, having a score of 8 or less means you’re in a coma. The lower the score, the deeper the coma is. A score of 3 is the lowest possible. The GCS measures three categories:

  • Eye response (1 - 4).
  • Motor response (1 - 6).
  • Verbal response (1 - 5).

What can cause a coma?

Many conditions and circumstances can cause or contribute to a coma.

What are some risk factors?

Some conditions and circumstances can increase your risk of having a coma. These include:


What complications are possible with a coma?

People who are in a coma can’t move, feed, bathe or otherwise take care of themselves, meaning they need 24/7 medical care. A person who’s in a coma needs to have a urinary catheter placed to collect urine (pee), and it’s common for people in a coma to need breathing assistance also, meaning they need mechanical ventilation (ventilator support to keep them breathing).

Some of the possible complications of a coma or coma-related care include:

Diagnosis and Tests

How is a coma diagnosed?

Finding the reason for the coma — including diagnosing an underlying medical condition — needs to happen quickly. One of the first steps to diagnosing a coma is a neurological exam. A healthcare provider can carry out this exam and then use a tool like the Glasgow Coma Scale to determine the severity of the coma.

In addition to the neurological exam, there are several tests that healthcare providers will use to try to find why the coma is happening and how severe the problem is. In cases of head injuries, for example, the cause is easier to identify, and tests will focus on determining how severe the damage is. When the cause isn’t known, finding the cause of the coma and determining the severity of the cause often happen at the same time.

What tests will be done to diagnose this condition?

Many tests can help diagnose a coma or determine how severe it is. These include:

  • Laboratory testing of blood, urine, cerebrospinal fluid (CSF) and more. These are extremely helpful for finding many causes of a coma. These can detect issues with blood sugar levels, electrolyte imbalances, organ failure, toxins and poisons, and more. They can also help find signs of infections.
  • Diagnostic imaging. These tests use varying methods to “look” inside your head for signs of injury or damage. Examples of the most common diagnostic imaging tests include computed tomography (CT) scans and magnetic resonance imaging (MRI) scans.
  • Electroencephalogram (EEG). This test detects and tracks your brain’s electrical activity. It can help determine the severity of a coma or detect signs of conditions that may cause a coma, like seizures and epilepsy.
  • Electrocardiogram (ECG or EKG). This test can help detect or rule out a heart rhythm problem that could have led to a coma.

Other tests are also possible, depending on the coma itself, your circumstances and your health history. A healthcare provider is the best person to explain what tests they recommend (if you have a loved one in a coma) or which tests they performed (if they’re talking to you after you regain consciousness).


Management and Treatment

How are comas treated, and is there a cure?

The treatment for a coma depends greatly on the underlying cause. Because comas can happen for so many reasons, there are many possible treatments. What works for one cause may not work for another (or might make another condition worse).

Because of that, a healthcare provider is the best person to tell you about the treatments that are possible and recommended in your or your loved one’s particular circumstance.

Common on-the-spot treatments

There are certain treatments that providers or caregivers may start before knowing what caused a coma. These treatments usually relate to known medical conditions, or they may relate to evidence around a person that indicates a possible cause of coma. These treatments may help stabilize a person, keeping the coma from worsening, or even reverse the coma entirely. Examples include:

  • Glucose or insulin. These can help raise or lower blood sugar levels. Glucose can rapidly reverse a coma when given in time.
  • Overdose-reversing medications. An example of this is naloxone, which can reverse opioid overdoses. Naloxone can reverse an opioid overdose in two to five minutes.

Complications/side effects of the treatment

Because there are so many different treatments for coma, there are also many possible complications and side effects of the treatments. Your healthcare provider is the best person to explain what side effects or complications are possible or likely, and what you can do about these.


Are comas preventable?

It’s possible to prevent — or reduce your risk of having — many of the conditions that cause comas. Some of the most important ways you can prevent or reduce your risk of being in a coma include:

  • Managing your chronic conditions. Following your healthcare provider’s guidance on managing chronic conditions like diabetes and epilepsy can lower your odds of being in a coma in the future.
  • Wearing safety equipment as needed. Head injuries, especially concussions and traumatic brain injuries, are very common causes of comas. When applicable, wear safety equipment like helmets and seat belts to protect yourself.
  • Eating a balanced diet. Many of the most common causes of coma are related to diet, like electrolyte imbalances and nutrient deficiencies. Your diet also affects your circulatory health, which can help you avoid comas related to conditions like stroke.
  • Staying physically active and maintaining a weight that’s healthy for you. Your weight and activity level can prevent or delay conditions that affect your brain, especially conditions that can lead to comas.
  • Avoiding substance and nonmedical drug use, and using alcohol in moderation. Substance use disorders greatly increase the risk of a coma. You should also take prescription medications as directed, as this reduces the risk of complications and side effects like a coma.

Outlook / Prognosis

What can I expect if I am in a coma?

Being in a coma generally means you’re not conscious, so you don’t know you’re in a coma. You don’t show any signs of awareness of the world around you, and you can’t intentionally react to your circumstances, environment or your body’s needs. Depending on the depth of your coma, you may still have some reflex responses, but these vary from case to case.

Can I hear or remember things that happened around me when I was in a coma?

This is sometimes possible, but it depends on the type of coma and how deep your coma is. There’s evidence that people in a coma can hear what’s happening around them. Some people who were in a coma can remember what they heard happening nearby. However, this can vary widely and it’s difficult to predict how and when a person might experience this.

It’s also important to remember that comas can be difficult to diagnose. Healthcare providers make this diagnosis using their training, experience and judgment, but no two cases are the same. That means it’s possible to misdiagnose a coma or misjudge its depth because of another factor. People may also be in a coma at first but recover enough to regain some awareness before a healthcare provider can recognize the change in awareness.

Because there are so many factors, there’s no easy way to answer this question. A healthcare provider is the best person to help you explore whether you or a loved one were aware or can remember what happened during a coma. While they may not be able to answer this question fully, they can at least help you understand what effect — if any — that knowledge can play in recovery and what comes next.

How long does a coma last?

A coma can be very brief and last only a few minutes, or it can last as long as one to two weeks. Unfortunately, death is a possible complication of being in a coma. This is more likely to happen when a coma happens because of a very severe injury or illness, or when a person doesn’t get medical care quickly enough after they enter a coma.

Comas rarely last longer than a couple of weeks because people tend to emerge from the coma and wake up or shift into another state of decreased or minimal consciousness. These include:

  • Vegetative state. A person in this state is awake but unaware of the world around them and doesn’t show any intentional behaviors. They may open their eyes or do things that look like reactions to the world around them, but they aren’t actually aware or acting intentionally. When a vegetative state lasts long enough, it’s known as a persistent vegetative state (experts define a vegetative state as “persistent” when it lasts at least three months when not related to trauma and at least 12 months when related to trauma).
  • Minimally conscious state. This is when a person shows some awareness of the world around them and some intentional behaviors. They can follow simple commands and say short phrases, but they can’t do these things consistently. When they can’t do these things, they appear similar to people with persistent vegetative states.

A vegetative state is similar to a coma but isn’t the same. People in a vegetative state have recovered enough that they aren’t in a coma, but their brain’s abilities and activity are still very limited.

The potential for recovery from a vegetative state varies widely. Some people recover consciousness fully or partially, but most don’t. People can remain in vegetative states for weeks, months or even years. However, they need constant medical care because they can’t care for themselves. Unfortunately, their risks of complications are high, and most people in a vegetative state have a limited life expectancy.

What’s the outlook for this condition?

The outlook for a coma can vary widely, and many factors play a role. The best person to tell you the outlook for a specific situation is a healthcare provider who knows the situation. In most cases, this is the provider caring for your loved one.

How to ensure your wishes are followed when you can’t choose yourself

If you’re in a coma, you can’t make decisions about your medical care or tell anyone what you want. In many cases, that means it falls to family or loved ones to make those choices.

Regardless of whether you have a condition that could cause a coma, it’s a good idea to have conversations with your loved one about what you want in case you can’t make decisions about your own medical care. These conversations may feel unpleasant or difficult, but having them sooner rather than later can ensure your loved ones know what you want if you can’t tell them or choose for yourself.

It’s also a good idea to put your wishes and decisions in writing. That typically involves preparing documents related to legal issues and what happens if you can’t take care of yourself or making decisions for your own care or well-being. You can consult an attorney for help preparing these documents, but many of them you can prepare on your own (you may need a notary or other official to endorse them, depending on the laws in your area).

A note from Cleveland Clinic

For those who have a loved one in a coma, it can be a frightening experience. You may have many unanswered questions when your loved one is in a coma. You may wonder whether they can recover, how long it will take and if a full recovery is possible. While living with questions and uncertainty isn’t easy, ongoing research is helping experts better understand how comas work and how to treat them. That will open the door for possible recovery from comas both now and in the future.

Medically Reviewed

Last reviewed on 03/06/2023.

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