How long can the human brain go without oxygen?

Even without being aware, we are exposed to many situations that could cause us to lack oxygen in the brain. Now what happens when that happens?

Although it represents 2% of our body weight, the brain consumes approximately 20% of the oxygen we take in, the percentages varying according to the brain area. For example, the sensitive and motor areas spend more. This consumption is continuous, since it has very little capacity to store nutrients. Therefore, the lack of oxygen to the brain can have serious consequences.

The brain can last 4 or 6 minutes without oxygen. Now, once that time has passed, cell damage begins to occur that will be greater the more time passes. In fact, if the lack of oxygen is sustained for more than 15 minutes, at least 95% of brain tissue will be damaged.

Human brain oxygen deprivation time

Have you ever wondered how long the human brain can go without oxygen before irreversible damage starts to show up? The answer is about 4 to 6 minutes. After that time, the brain damage becomes irreversible and can lead to death.

It is important to understand the effects of oxygen deprivation on the human brain in order to prevent life-threatening situations. This is especially important for those who work in environments where oxygen deprivation can be a problem, such as on submarines or on airplanes.

Consequences of oxygen deprivation of the human brain

Ultimately, the consequence of oxygen deprivation is brain damage and even death. More specifically, the lack of oxygen first causes a loss of consciousness or a coma. After this period it could fall into a vegetative state.

If the person regains consciousness, then symptoms similar to those of a head injury occur. Thus, the severity of the damage and the symptoms will depend on the anoxia and personal characteristics: duration, age of the person, if another associated disease is suffered, the duration of the coma and the extent, location and spread of the lesion.

Cognitive alterations

In relation to cognitive functions, the main symptom is loss of short-term memory or learning ability. This seems to be because the hippocampus, an area heavily involved in learning new information, is highly sensitive to lack of oxygen. On the other hand, anoxia can affect executive functions, causing the person to be more impulsive, indecisive and have difficulties reasoning and processing information.

Visual disturbances can also occur, it can even lead to cortical blindness. That is, the image is received but it cannot be processed at a conscious level, therefore the person cannot see. However, the person who suffers from it acts as if they were seeing, but being unable to identify colors, shapes or objects.

Physical alterations

In addition, the lack of oxygen can cause physical alterations, such as lack of coordination (ataxia), which is an obstacle to walking correctly. Or, apraxia, which is the inability to properly perform the sequence of daily tasks, such as brushing teeth. Body rigidity, spasms or involuntary movements, as well as weakness in the extremities can also occur.


After an episode of anoxia or hypoxia, epilepsy or a similar picture consisting of epileptic seizures or muscle jerks may also develop.

Also, especially if the anoxia is in a neonate, cerebral palsy can occur. On the other hand, it is common to find disorders at the level of consciousness, where there are prolonged states of low response to the environment.