Unconsciousness - causes and signs

Unconsciousness - causes and signs

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Unconsciousness knows many names: fainting, blackout or collapse. Fainting means total helplessness for a while. This usually takes less than 20 seconds, but that's no reason to consider it harmless. If our brain is not supplied with blood, we faint after a few seconds.

Fainting leads to falls and can cause injuries. Unconsciousness announces itself beforehand, through nausea, feelings of heat, a gut feeling or weak knees, but sometimes it hits us without any signal. We can faint anytime, anywhere - on the steering wheel of a car at a speed of 160 as well as when we cross a busy street. Fatal accidents resulting from fainting are therefore a real danger.


All signs of fainting can also be symptoms of other symptoms. This includes dizziness, drowsiness, loss of orientation, poor eyesight (in which we see things like blurring, stars flicker in front of our eyes or we cannot estimate distances), sweaty hands and nausea.

With these symptoms, you should lie down flat and put your legs up. As a result, the blood flows from the legs into the heart and the blood pressure increases. You can avoid fainting or at least shorten it. If you are lying down, you cannot fall.

The reasons

Fainting does not necessarily indicate serious illnesses. The triggers can be harmless: they jump off the bed too quickly in the morning, they are exhausted after physical work; your body is overheated (this includes fainting during a so-called sunstroke) or you suffer from negative stress. Emotional arousal can also lead to unconsciousness: fainting at the sight of the dream man or dream woman is not an invention of Hollywood directors and paramedics have relevant experience with teenagers who have a blackout at Tokio Hotel concerts.

Fainting is more serious as a result of irregular heartbeat, drug and alcohol abuse, illnesses or medication. The following applies here: sudden fainting recurrences are a serious symptom and you should see a doctor as soon as possible to prevent worse things from happening.
Fainting with harmless triggers can also have psychological consequences: About a third of all people who lose consciousness suffer from compulsive anxiety or even clinical depression. Those affected avoid situations that remind them of fainting or could be potentially dangerous: for example, they no longer drive a car or withdraw to the desk. Some are afraid of being alone, others panic when crossing streets.

Serious causes of loss of consciousness

Abnormal blood flow to the brain can also be caused by abrupt movements, heat and exertion, but there are sometimes far worse symptoms: Brain injuries or a stroke, bleeding in the brain or clogged blood vessels are serious brain disorders that can cause fainting.

Another cause is metabolic disorders: poisoning from drugs, alcohol and medication, diabetes, liver weakness or thyroid disorders. Brain dysfunction is also a possible cause: it can be a brain tumor or a brain infection.

A brief fainting spell is usually due to a short-term disturbance in the cerebral blood flow. That is, one of the nervous systems that control cardiac functions temporarily ceases to function, especially on the heart or carotid arteries. Martial artists learn, for example, how to knock an opponent out of action by hitting the edge of their hands against the carotid artery.

How does unconsciousness show up?

The consciousness is so limited that the senses fail and they can no longer control parts of their bodies. For example, they fall off the chair because they can no longer control their muscles, or they make their pants loose because the sphincters fail.

Those affected do not have to fall in all forms of unconsciousness. In some cases, they maintain control over certain regions of their bodies. Falls from epileptic seizures, hypoglycaemic patients and patients with increased intracranial pressure are typical.

Epileptics also know of seizures in which their consciousness is “only” disturbed, but not completely stopped. Even small blood clots in the brain lead to such a short-term disturbance in the blood circulation in the brain that the people affected are stunned for a moment, but do not faint completely. These people see everything around them "as if through a veil".

Those who faint for a moment often remember exactly how they felt sick or suddenly a “shadow appeared before their eyes”, “flickered” before their eyes or the edges of their field of vision narrowed. Prolonged loss of consciousness is usually associated with amnesia.

Heart failure

Fainting combined with chronic shortness of breath are a warning sign of heart failure. The heart muscle is unable to conduct the oxygenated blood into the muscles.

Blood loss

A high blood loss almost automatically leads to unconsciousness. Access to the brain is not blocked here, but there is not enough blood left to fill the vessels. It only helps to stop the flow of blood from the wound immediately and a blood transfusion.

What helps?

If fainting occurs due to a basic illness such as diabetes, epilepsy, heart failure or brain diseases, then the disease must be treated itself. However, short, one-time faintings can be prevented with prudent behavior.


Exercise in moderation strengthens the cardiovascular system and gives blood to the brain because the blood receives more red blood cells and transports more oxygen. The blood flows better and takes up more oxygen. The cells have more mitochondria that convert energy sources into energy. This also makes the body use oxygen more effectively, because the capillaries around the alveoli become denser and more oxygen comes from the lungs into the blood.

Avoid abrupt movements, especially if you have previously been at rest. After sleep, the circulation takes some time to "get going". In the worst case, if you jump out of bed too quickly, you can interrupt the blood flow to the brain.

Avoid stress

Control negative stress. Do tasks one by one and don't try to do everything at the same time. With overwhelming fears, ask yourself what reality looks like, design a "worst case scenario" and think about what could actually happen. Interrupt activities in closed rooms by taking walks in the fresh air. Take a deep breath, oxygen is one of the best triggers to keep blood flow going.

Sun protection

Prepare yourself systematically on strenuous tours in hot countries. Cover your head, carry enough drinking water with you, and have a linen towel ready to provide shade in treeless plains. If you are not used to physical work, take sufficient breaks. This not only prevents fainting, but also increases work performance.

Everyone according to their abilities

Avoid extreme sports if you are not properly trained. When you start weight training, only do the exercises until you feel the first pain or can no longer breathe evenly. If "old hands" laugh at you at the gym because of that, change the studio. Any responsible coach will advise you never to overload yourself.

If you are exhausted, don't let perseverance slogans influence you like "we all had to go through". It is their organism, and maybe the "others" ended up in the hospital after a circulatory collapse.

Be careful with drugs and alcohol: a light intoxication may be pleasant, but it may not be unconscious during alcohol poisoning. Beware of, in the literal sense, "binge drinking".

First aid

If someone else faints in their presence, apply first aid. Place the person in a stable side position and, if possible, raise their legs so that the blood can flow into the brain. In any case, call an ambulance. You do not decide whether it is a harmless trigger or a serious illness. (Dr. Utz Anhalt)

Author and source information

This text corresponds to the specifications of the medical literature, medical guidelines and current studies and has been checked by medical doctors.

Dr. phil. Utz Anhalt, Barbara Schindewolf-Lensch


  • Michael Buchfelder; Albert Buchfelder: First Aid Manual, Schattauer, 2006
  • Erland Erdmann: Clinical Cardiology, Springer, 2009
  • Hans Walter Striebel: Anesthesia - Intensive Care Medicine - Emergency Medicine: For study and training, Schattauer, 2012
  • Claudio Bassetti; Marco Mumenthaler: Neurological differential diagnosis: correctly assessing, clarifying and classifying neurological symptoms and signs, Thieme, 2012

Video: Treating Traumatic Brain Injuries (August 2022).