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How Long Can The Brain Go Without Oxygen


It is incredible how an organ weighing only three pounds (our brain) is responsible for the functionality of the whole human body. While the body’s functions rely on the brain, it depends on oxygen to function properly. A human brain without oxygen is just like a little organ that’s of no use.

The human brain needs 20% oxygen to work and keep the other body’s functions healthy. If a person’s brain does not receive oxygen, they are declared brain-dead, called Cerebral Anoxia/Hypoxia. So, the question arises: what happens to the brain without oxygen?

What is Cerebral Hypoxia?

When your brain does not receive enough blood, it is called Cerebral Hypoxia. In such a condition, blood and oxygen supply are usually not compromised throughout the body, but it does not reach the brain. Cerebral Hypoxia may be a result of disturbed blood supply due to drowning or cardiac arrest.

Unlike Hypoxia, the blood supply, including RBCs and WBCs, to the brain diminishes completely in Cerebral Anoxia. It is the condition when no blood reaches the brain and brain cell death begins. The blood and oxygen flow to the brain may stop due to drowning, strangling, cardiac arrest, or others.

When presented with a brain injury resulting from a lack of oxygen supply, doctors usually called it a hypoxic-anoxic brain injury.

What are the Reasons for Cerebral Hypoxic-Anoxic Injury?

Hypoxic-Anoxic Brain Injury may be caused as a result of

High altitude

Traveling or trekking above a height of 8,000 ft. results in decreased oxygen supply to the body.

Asthma attack


Some medical conditions like asthma and COPD make it difficult to breathe, causing a diminished oxygen supply to the brain.


Drinking or eating too quickly can cause choking and obstruct the windpipe.


Being in an enclosed space or while someone is being strangled, they experience a restriction of the oxygen supply, resulting in Hypoxia.


A stroke usually occurs due to a clot that stops the blood flow, reducing the oxygen supply to the brain.


Sometimes, the body struggles to find oxygen and breathe in deep water, causing Hypoxia and eventually Anoxia.

Symptoms of Cerebral Hypoxia

Cerebral Hypoxia is caused by one or other underlying reasons and presents itself in varying forms, including

  • Rapid breathing and heartbeat
  • Decreased blood circulation in feet and hands
  • Stuttering
  • The lips and skin get a bluish tint
  • Dilated pupils
  • Seizures or convulsions
  • Fainting

If a person experiences Hypoxia or Anoxia due to stroke, the patient also exhibits signs of unresponsiveness.

How Long Can The Brain Go Without Oxygen

When your brain experiences Hypoxia, it is reversible by providing timely treatment such as treating the stroke or offering oxygen to improve the oxygen supply to the brain. When the brain does not receive any oxygen (Cerebral Anoxia), brain death occurs within 10 – 15 minutes.


There’s an entire process of brain cell damage, so it is essential to understand how long can the brain survive without oxygen. Below is a complete stage of the brain being deprived of oxygen for a specific time. It is as:

The Brain without Oxygen for 30 sec – 3 mins

As we now know, oxygen is pretty significant for the proper functioning of the brain. However, if a human brain is deprived of oxygen for more than 30 seconds till it reaches 3 minutes, the person starts losing consciousness.

The Brain without Oxygen for 1 minute

Right after 1 minute of being without oxygen, the brain cells gradually start dying.

The Brain without Oxygen for 3 minutes

This is where neurons suffer extra damage, and there are fewer chances of brain cell recovery.

The Brain without Oxygen for 5-15 minutes

Unfortunately, if the brain is unable to receive oxygen for more than 5 minutes, it causes a coma (state of unconsciousness), rapid seizures, and even brain death at a point.

The Brain without Oxygen for 20 minutes

If the painful process stays persistent for an extended time, like 20 minutes, the neural cells start dying through a typical process called apoptosis. It results in diminished brain functioning and irreversible brain damage.


What else can cause Anoxia?

Cerebral Anoxia may be caused by other reasons like carbon monoxide poisoning or breathing in smoke. Carbon monoxide poisoning can sometimes be asymptomatic but causes death.

How is Hypoxia treated?

There is no definite treatment for Hypoxia; however, the underlying cause must be treated as soon as possible to avoid irreversible brain damage.

How does a Cardiac arrest cause Hypoxia?

The heart stops beating within 20 seconds of the cardiac arrest, and the lack of blood supply to the brain causes Hypoxia that may lead to Cerebral Anoxia.

1 thought on “How Long Can The Brain Go Without Oxygen”

  1. Can you possibly give advice for someone who appears to be mostly brain dead but is still breathing on his own and has reactive pupils and open and closes eyes! The brain injury was caused by approx 10 min without oxygen to his brain after being shot.

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