Fainting

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Introduction

What is fainting?

Fainting is temporary loss of consciousness that occurs from an interruption of, or decreased amount of, blood supply to the brain. It may be preceded by the sensation of feeling lightheaded or unsteady, as if you will lose your balance, or a feeling that things are spinning around you. Fainting and dizziness may be accompanied by other symptoms, such as nausea with or without vomiting, perspiration, and trembling. The medical term for fainting is syncope.

Blood supplies oxygen to the brain. Fainting occurs when blood is not getting to the brain quickly enough or if there is a deficit of blood. Certain conditions that cause dizziness and loss of consciousness include orthostatic hypotension (drops in blood pressure from standing too quickly), hunger, hypoglycemia (low blood sugar), dehydration, or heart problems. Feelings of anxiety, panic and fear can also result in fainting.

Some medications are also associated with fainting or loss of consciousness. These include blood pressure medications, allergy medications, and diabetes medications.

Feeling lightheaded and dizzy can be signs of a potentially life-threatening condition, such as a heart attack, stroke, or shock (a severe blood pressure drop). Seek immediate medical care (call 911) if you experience dizziness accompanied by feelings of pain or pressure in your chest, speech problems, shortness of breath, sudden weakness or numbness on one side of the body, chest pain that radiates down the arm or to the jaw, or alterations in vision.

Symptoms

What other symptoms might occur with fainting?

Fainting may accompany other symptoms that vary depending on the underlying disease, disorder or condition.

Symptoms that may occur along with fainting

Fainting may accompany other symptoms including:

  • Chest pain or pressure
  • Dehydration
  • Difficulty hearing
  • Dizziness or lightheadedness
  • Headache
  • Nausea with or without vomiting
  • Pale skin (pallor)
  • Perspiration
  • Shaking or trembling
  • Vision problems

Serious symptoms that might indicate a life-threatening condition

In some cases, fainting may be a symptom of a life-threatening condition that should be immediately evaluated in an emergency setting. Seek immediate medical care (call 911) if you, or someone you are with, have any of these life-threatening symptoms including:

  • Chest pain or tightness
  • Convulsions or seizures
  • Difficulty breathing, talking, or swallowing
  • High fever (higher than 101 degrees Fahrenheit)
  • Loss of consciousness
  • Stiff neck
  • Vomiting
Causes

What causes fainting?

A number of conditions can cause you to feel dizzy or lightheaded, which occurs when the brain does not get enough oxygen. These include hunger, fatigue, hypoglycemia (low blood sugar), or anxiety. Fainting can also occur from violent coughing fits or straining from urination or defecation. Feelings of anxiety, panic and fear can also result in fainting. Nearly half the time, the precise cause of the fainting episode is never identified

Some medications are also associated with fainting or loss of consciousness. These include blood pressure medications, allergy medications, and diabetes medications.

Common causes of fainting

Fainting may can be caused by the following:

  • Anxiety, fear or panic
  • Dehydration
  • Excessive or violent coughing
  • Hunger or hypoglycemia (low blood sugar)
  • Hyperventilation
  • Low blood pressure
  • Medication side effects
  • Orthostatic hypotension (drops in blood pressure from standing too quickly)
  • Pregnancy
  • Straining during bowel movements
  • Urination

Serious or life-threatening causes of fainting

In some cases, fainting or loss of consciousness may be a symptom of a serious or life-threatening condition that should be immediately evaluated in an emergency setting. These include:

    Questions for diagnosing the cause of fainting

    To diagnose your condition, your doctor or licensed health care practitioner will ask you several questions related to your fainting including:

    • How long have you been experiencing fainting spells and dizziness?
    • How often do you feel faint?
    • Do you have other symptoms in addition to the fainting spells and dizziness?
    • Did your symptoms occur with or after an illness?
    • Have you ever hit your head or injured yourself as a result of fainting?
    • Do seizures accompany the fainting?
    • Have you recently experienced a head trauma?
    • What medications are you taking?

    What are the potential complications of fainting?

    Because fainting can be due to serious diseases, failure to seek treatment can result in serious complications and permanent damage. Once the underlying cause is diagnosed, it is important for you to follow the treatment plan that you and your health care professional design specifically for you to reduce the risk of potential complications including:

    • Brain damage
    • Coma
    • Heart disease
    • Motor vehicle accidents
    • Permanent physical disability
    • Spread of cancer
    • Trauma
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    Medical Reviewer: William C. Lloyd III, MD, FACS
    Last Review Date: 2018 Nov 18
    1. Fainting. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/003092.htm
    2. Alertness - decreased. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/ency/article/003202.htm
    3. Tierney LM Jr., Saint S, Whooley MA (Eds.) Current Essentials of Medicine (4th ed.). New York: McGraw-Hill, 2011.
    4. Domino FJ (Ed.) Five Minute Clinical Consult. Philadelphia: Lippincott Williams & Wilkins, 2013.
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