Fainting

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What is fainting?

The definition of fainting is a temporary loss of consciousness. It occurs when blood is not getting to the brain quickly enough or there is not enough blood going 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. Other fainting symptoms may occur along with a loss of consciousness, 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.

What are the different types of syncope (fainting)?

There are several different types and subtypes of syncope.

Neurally mediated, or reflex syncope

Reflex syncope is the most common type. It occurs when a reflex response causes blood vessels to dilate and the heart rate to slow, leading to low blood pressure and decreased blood flow to the brain. Young adults are most likely to have this type of syncope.

There are three types of reflex syncope:

  • Vasovagal, which is the most common of all types of fainting. Vasovagal syncope occurs when the vagus nerve triggers a sudden decrease in blood pressure and heart rate. Common stimuli include heat exposure, emotional stress, fear, distress, and events that can potentially or actually cause pain.
  • Situational, which is similar to vasovagal, but only occurs during certain actions or situations. This includes coughing, urinating, after eating, after exercising, or upon sudden startling or pain.
  • Carotid sinus syndrome, which is the least common reflex syncope. It occurs when there is too much pressure on the carotid arteries in your neck. These arteries carry oxygen-rich blood to your brain. Common triggers include rotating your head too quickly or too much, wearing a tight collar, and shaving.

Cardiac syncope

Cardiac syncope is related to problems with the heart. It is the second most common type of syncope after reflex syncope. Fainting is the result of the heart not being able to pump out enough blood. Most cases of cardiac syncope are due to arrhythmias. Structural and mechanical heart problems can also cause it. Older adults are more likely to suffer with cardiac syncope. However, cardiac syncope due to arrhythmia is often the cause of sudden death in young adults.

Neurologic syncope

Neurologic syncope is the result of a neurologic or cerebrovascular condition. This includes seizures, stroke, TIA (transient ischemic attack), basilar artery disease, and even migraine.

Orthostatic or postural syncope

Postural syncope occurs when you change positions and blood pressure drops too quickly. This can happen with dehydration, blood loss, low blood sugar, and several other diseases, disorders and conditions. Certain medications can also cause it, such as blood pressure, allergy, and diabetes medications.

Psychogenic syncope

Psychogenic syncope occurs with mental health disorders, such as depression, anxiety disorders, and panic disorders.

POTS (Postural Orthostatic Tachycardia Syndrome)

POTS is a rare disorder that tends to affect women more than men. It occurs when the heart rate goes very high after a person rises from a sitting or lying down position. The very rapid heart rate interferes with the heart’s ability to pump out enough blood.

Unknown syncope

Unfortunately, the cause of syncope is unknown in up to a third of cases.

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 with 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.

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
  • Difficulty hearing
  • Dizziness or lightheadedness
  • 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
  • Difficulty breathing, talking or swallowing
  • High fever (higher than 101°F)
  • Loss of consciousness
  • Vomiting

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), and anxiety. Fainting can also occur from violent coughing fits or straining from urination or a bowel movement. 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 occur due to the following:

  • Anxiety, fear or panic
  • Dehydration
  • Excessive or violent coughing
  • Hunger or hypoglycemia (low blood sugar)
  • 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:

  • Brain hemorrhage
  • Cardiac disease: arrhythmia, valve dysfunction
  • Seizures
  • Severe blood loss
  • Shock
  • Stroke

When should you see a doctor for fainting?

The most common cause of fainting, vasovagal fainting, is usually not a serious problem. However, there are times when you should see a doctor in case there is a more serious cause. Make an appointment to see your doctor as soon as possible if you have never fainted before and faint for no apparent reason. See a doctor right away if you are fainting often or if new symptoms occur along with fainting.

Call 911 or go to your nearest emergency room for fainting when:

  • The person cannot speak, understand speech, see normally, or move one side of the face or body.
  • The person does not regain alertness within a couple of minutes.
  • The person has convulsions or loses bowel or bladder control.
  • The person has fallen, hit their head upon fainting, or is injured or bleeding.
  • The person is diabetic, pregnant, or over age 50.

How do doctors diagnose the cause of fainting?

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

  • How long have you been experiencing fainting spells?
  • How often do you feel faint, lightheaded or dizzy?
  • Do you have other symptoms in addition to fainting spells?
  • 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?

Your doctor will also conduct a physical exam, focusing on the heart, lungs, nervous system, and blood pressure. The exam may reveal clues to guide further testing. Possible tests your doctor may recommend include:

  • Autonomic reflex testing, which checks the nerves that control bodily functions, such as heart rate and blood pressure
  • Blood volume and hemodynamic tests to see if you have enough blood in your body and how it flows when your heart contracts
  • Lab tests, including blood and urine tests

It is not always possible to diagnose an underlying cause or condition. If the problem persists and your provider is unable to determine a cause, seeking a second opinion may give you more information and answers.

How do you treat fainting?

The goal of treating syncope is to avoid future episodes of fainting. Treatments for fainting depend on the type of syncope and the underlying cause. When fainting is due to an underlying medical condition, treating the condition will help resolve the fainting. Depending on the condition, this may involve medications, surgery, or another minor procedure. If medications are the cause (or a possible cause), your doctor may recommend adjusting the dose or trying an alternative drug. In some cases, support garments, such as compression stockings, may be helpful.

Home remedies for fainting

Your doctor may recommend certain lifestyle changes to help reduce the chances of fainting. This includes:

  • Avoiding triggers of vasovagal syncope, such as heat exposure
  • Changing your diet to increase salt and fluid intake, limit caffeine and alcohol use, and eat smaller, but more frequent meals
  • Standing up and changing positions slowly and deliberately

Alternative treatments for fainting

Biofeedback may help certain people with syncope. Working with a therapist, you can learn to control your heart rate. You can also use biofeedback to control mental reactions to situations and stimuli. For people with vasovagal syncope due to emotional stress, fear, or the thought of pain, cognitive behavioral therapy can also help you understand and change your reactions.

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 healthcare professional design specifically for you to reduce the risk of potential complications including:

  • Brain damage
  • Coma
  • Motor vehicle accidents as a result of fainting
  • Permanent physical disability
  • Trauma as a result of injury from fainting
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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Mar 17
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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