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By Medicover Hospitals / 20 Feb 2021
Home | symptoms | fainting
  • Temporary and sudden fainting or loss of consciousness. This usually happens due to a lack of oxygen reaching the brain. Many factors can lead to oxygen deprivation in the brain, including low blood pressure. Fainting is usually not serious. However, sometimes it can indicate a serious medical problem.
  • Article Context:

    1. What is fainting?
    2. Causes
    3. Diagnosis
    4. Treatment
    5. When to visit a Doctor?
    6. Prevention
    7. FAQ's

    What is fainting?

  • Fainting, which healthcare professionals call syncope, is a temporary loss of consciousness. Fainting is caused by a temporary loss of blood supply to the brain and may be a sign of more serious illness. People of any age can faint, but older people can have a serious underlying cause. Fainting represents a small portion of emergency room visits and 6% of hospital admissions. The most common causes of fainting are vasovagal disease (sudden drop in heart rate and blood pressure) and heart disease. Most fainting, the cause is unknown.
  • Types of Fainting:

  • In addition to distinguishing fainting episodes based on their underlying cause, one of two different types of fainting can occur:
  • Pre- or near-syncope: This occurs when a person can remember events or sensations when losing consciousness, such as dizziness, blurred vision, and muscle weakness. They may remember falling before hitting their head and passing out.
  • Syncope: This occurs when a person can remember the sensations of dizziness and loss of vision, but not the fall itself.
  • Causes:

  • Fainting is usually the result of a lack of oxygen to the brain, such as problems with the lungs or blood flow, or carbon monoxide poisoning.
  • Fainting is a survival mechanism. If the blood and oxygen levels in the brain drop too low, the body immediately begins to shut down non-vital parts to direct resources to vital organs.
  • When the brain detects lower levels of oxygen, breathing quickens to increase the levels.
  • The heart rate will also increase, so more oxygen will reach the brain. This lowers the blood pressure in other parts of the body. The brain then receives additional blood at the expense of other areas of the body.
  • Hyperventilation associated with hypotension can lead to short-term loss of consciousness, muscle weakness, and fainting.
  • Different underlying causes can cause fainting. We discuss some of them in detail below:
  • Neurocardiogenic Syncope:

    • Neurocardiogenic syncope develops due to short-term autonomic nervous system (ANS) dysfunction. Some people call it neuron mediated syncope (NMS).
    • The ANS controls automatic bodily functions, including heart rate, digestion, and respiratory rate.
    • In NMS, a drop in blood pressure slows the heart rate and pulse. This temporarily cuts off the blood and oxygen supply to the brain.
    • Possible triggers for neurocardiogenic syncope include:
      • an unpleasant or shocking image, such as seeing blood
      • sudden exposure to an unpleasant sight or experience
      • sudden emotional upheaval, as after receiving tragic news
      • extreme embarrassment
      • motionless for a long time
      • strenuous physical activities, such as lifting a heavyweight

    Orthostatic Hypotension:

    • Orthostatic hypotension refers to fainting after getting up too quickly from a sitting or horizontal position.
    • Gravity draws blood to the legs, lowering blood pressure elsewhere in the body. The nervous system usually responds to this by increasing the heart rate and narrowing the blood vessels. This stabilizes the blood pressure.
    • However, if anything interferes with this stabilization process, there may be a poor supply of blood and oxygen to the brain, which leads to fainting.
    • Triggers include:
      • Dehydration: If body fluid levels drop, blood pressure will also drop. This can make it harder to stabilize blood pressure. As a result, less blood and oxygen reach the brain.
      • Uncontrolled diabetes: A person with diabetes may need to urinate frequently, resulting in dehydration. High blood sugar can damage certain nerves, especially those that regulate blood pressure.
      • Certain medications: Taking diuretics, beta-blockers, and antihypertensive drugs can cause postural hypotension in some people.
      • Alcohol: Some people pass out if they drink too much alcohol in a short time.
      • Certain Neurological Conditions: Parkinson's disease and other neurological disorders affect the nervous system. This can lead to orthostatic hypotension.
      • Carotid sinus syndrome: The carotid artery is the main artery that supplies the brain with blood. When there is pressure on the pressure sensors, or the carotid sinus, in the carotid artery, it can cause fainting.
    • If a person's carotid sinus is very sensitive, blood pressure may drop when they turn their head to one side, wear a tight collar or tie, or move over the carotid sinus while shaving. This can lead to fainting.

    Cardiac Syncope:

  • An underlying heart problem can reduce the supply of blood and oxygen to the brain. Possible heart problems include:
    • arrhythmias or abnormal heart rhythm
    • stenosis or blockage of heart valves
    • hypertension or high blood pressure
    • a heart attack, in which the heart muscle dies due to a lack of blood and oxygen
  • This cause of fainting usually requires immediate medical treatment and careful monitoring.
  • Diagnosis:

  • To diagnose your condition, your doctor or licensed health care professional will ask you several questions related to your fainting, including:
    • How long have you had fainting and dizziness?
    • How often do you feel weak?
    • Do you have any other symptoms besides fainting and dizziness?
    • Did your symptoms appear with or after illness?
    • Have you ever hit your head or injured yourself as a result of fainting?
    • Do seizures accompany fainting?
    • Have you recently suffered a head injury?
    • What medications do you take?


    • Treatment for fainting will depend on your doctor's diagnosis.
    • If there are no underlying medical conditions that are causing you to pass out, you usually won't need treatment and the long-term outlook is good.

    When to visit a Doctor?

  • Because fainting can be caused by serious illness, all fainting episodes should be taken seriously. Anyone who has the first episode of fainting should be evaluated by a healthcare professional as soon as possible. If the patient has a history of fainting and a specific diagnosis explaining the syncopal episodes, they should still inform the healthcare professional that they have had another fainting episode. The healthcare professional can decide whether the patient should be evaluated. Although most people with a history of vasovagal, situational, or postural fainting do not require hospitalization, many physicians prefer that anyone who faints or has a "short loss of consciousness" be seen by a healthcare professional.
  • Preventions:

    • If you have a history of fainting, try to find out what causes you to pass out so you can avoid these triggers.
    • Always get up slowly from a sitting or lying position. If you tend to feel faint at the sight of blood when having blood or other medical procedures, talk to your doctor. They can take certain precautions to prevent you from passing out.
    • Finally, don't skip meals.
    • Feeling dizzy and faint, and having a sensation of spinning are warning signs of fainting. If you notice any of these signs, sit down and place your head between your knees to help bring blood to your brain.
    • You can also lie down to avoid injury from a fall. Don't get up until you feel better.

    Frequently Asked Questions:

  • Lack of blood to the brain causes loss of consciousness. Most fainting will pass quickly and not be severe. Usually, fainting will only last a few seconds, although the person will feel unwell and recovery may take several minutes.
  • You feel lightheaded, dizzy, weak, or nauseous before passing out. Some people find that the noises fade or describe the sensation as "blackout" or "whiting out." Full recovery usually takes a few minutes.
  • Some people feel light-headed or lightheaded before they pass out. Others may have nausea, sweating, blurred or tunnel vision, tingling of the lips or fingertips, chest pain, or palpitations. Less often, people suddenly pass out without any warning symptoms.
  • Citations:

  • Vasovagal Fainting -
  • Fainting on exposure to phobic stimuli -
  • Prediction of Fainting in Blood Donors -