Read below about fainting, including causes and common questions. Or get a personalized analysis of your fainting from our A.I. health assistant. At Buoy, we build tools that help you know what’s wrong right now and how to get the right care.

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A.I. Health Assistant Causes for Fainting

The list below shows results from the use of our A.I. Health Assistant by Buoy users who experienced fainting. This list does not constitute medical advice.

  1. 1.Orthostatic Syncope (Fainting)

    Orthostatic syncope refers to a type of loss of consciousness caused by rapidly standing up from a sitting position, and not enough blood reaches the head. This can cause a person to pass out, but then come back to consciousness without lasting effects.

    1/3 of people report experiencing similar episode within 3 years.

    Rarity:
    Uncommon
    Top Symptoms:
    lightheadedness, brief fainting episode, dizziness and lightheadedness before passing out, fainting after standing up, fainting for the first time
    Symptoms that always occur with orthostatic syncope (fainting):
    brief fainting episode, fainting after standing up
    Urgency:
    Phone call or in-person visit
  2. 2.Stroke or Tia (Transient Ischemic Attack)

    A stroke is a medical emergency. Strokes happen when blood flow to the brain is stopped.

    Indefinite

    Rarity:
    Common
    Top Symptoms:
    dizziness, leg numbness, arm numbness, new headache, stiff neck
    Symptoms that never occur with stroke or tia (transient ischemic attack):
    bilateral weakness
    Urgency:
    Emergency medical service
  3. 3.Vasovagal Syncope

    Vasovagal syncope is one of the most common causes of fainting. Vasovagal syncope occurs when the body overreacts to certain triggers, such as the sight of blood or extreme emotional distress. The body coordinates a sudden drop of heart rate and blood pressure, causing reduced blood flow to the brain and a brief loss of consciousness.

    No treatment is needed.

    Rarity:
    Common
    Top Symptoms:
    lightheadedness, brief fainting episode, having fainted multiple times, fainting after standing for a long time, fainting episode after a specific trigger
    Symptoms that always occur with vasovagal syncope:
    brief fainting episode, having fainted multiple times
    Urgency:
    Phone call or in-person visit
  4. 4.Concussion Not Needing Imaging

    A traumatic brain injury (TBI), or concussion, happens when a bump, blow, jolt, or other head injury causes damage to the brain. Every year, millions of people in the U.S. suffer brain injuries. More than half are bad enough that people must go to the hospital, and the worst injuries can lead to permanent brain damage or death.

    Most patients with mild brain injury recover within hours to days.

    Rarity:
    Common
    Top Symptoms:
    dizziness, irritability, depressed mood, difficulty concentrating, trouble sleeping
    Symptoms that always occur with concussion not needing imaging:
    head or face injury
    Symptoms that never occur with concussion not needing imaging:
    recent fall from 6 feet or higher, severe vomiting, posttraumatic amnesia over 30 minutes, slurred speech, fainting, moderate vomiting
    Urgency:
    Primary care doctor

    Fainting Checker

    Take a quiz to find out why you’re having fainting.

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  5. 5.Narrowing of the Aortic Valve

    The aorta is the main artery that carries blood out of the heart to the rest of the body. Blood flows out of the heart and into the aorta through the aortic valve. In aortic stenosis, the aortic valve does not open fully, which decreases blood flow from the heart.

    Indefinite

    Rarity:
    Uncommon
    Top Symptoms:
    fatigue, shortness of breath, chest pain, shortness of breath on exertion, decreased exercise tolerance
    Urgency:
    Hospital emergency room
  6. 6.Hypertrophic Cardiomyopathy

    Hypertrophic cardiomyopathy (HCM) is a disease in which the heart muscle (myocardium) becomes abnormally thick (hypertrophied). This happens sometimes as a result of long-term elevated blood pressure, and sometimes without any particular reason. The thickened heart muscle can make it harder for the heart to pump blood.

    Hypertrophic cardiomyopathy is a life-long condition, as the heart walls are permanently enlarged.

    Rarity:
    Rare
    Top Symptoms:
    fatigue, shortness of breath, dizziness, racing heart beat, shortness of breath on exertion
    Urgency:
    Primary care doctor
  7. 7.Dehydration

    Dehydration occurs when the body does not have fluid to function properly, because of decreased intake or increased losses like vomiting and diarrhea. Symptoms of dehydration include extreme thirst, dark urine, fatigue, and dizziness.

    With rehydration, symptoms resolve completely.

    Rarity:
    Rare
    Top Symptoms:
    fatigue, dizziness, vomiting or diarrhea, racing heart beat, being severely ill
    Urgency:
    Hospital emergency room
  8. 8.Heart Attack

    Most heart attacks happen when a clot in the coronary artery blocks the supply of blood and oxygen to the heart. Often this leads to an irregular heartbeat - called an arrhythmia - that causes a severe decrease in the pumping function of the heart.

    Indefinite

    Rarity:
    Uncommon
    Top Symptoms:
    chest pain, shortness of breath, tight, heavy, squeezing chest pain, being severely ill, nausea
    Urgency:
    Emergency medical service
  9. 9.Long Qt Syndrome

    Long QT syndrome (LQTS) is a disorder of the heart's electrical activity. It can cause sudden, uncontrollable, dangerous arrhythmias in response to exercise or stress. Arrhythmias are problems with the rate or rhythm of the heartbeat.

    Resolves after stopping medication that causes it

    Rarity:
    Common
    Top Symptoms:
    racing heart beat, brief fainting episode, not having protected the body during the fall, feeling completely normal before fainting
    Urgency:
    Primary care doctor

FAQs About Fainting

Here are some frequently asked questions about fainting.

How do you feel when you are about to faint?

Fainting or syncope refers to a rapid onset loss of consciousness that is short in duration, typically caused by a decrease in blood flow to the brain. Before you lose consciousness, you may experience symptoms such as lightheadedness, sweating, and nausea.

Why do I faint after I get up in the morning?

When you sit or stand up in the morning, your brain is elevated above your heart, and thus it requires a higher pressure to supply blood to your brain. Your body accomplishes this by constricting your vessels throughout your body to maintain blood pressure. You may experience an initial decrease in blood pressure upon sitting or standing up which may cause you to faint. This is particularly true if you are dehydrated and get up quickly. Thus, fainting occurs more frequently in the mornings when you may have just spent eight hours without any fluid intake.

Why does the sight of blood make me faint?

When you are in the presence of a stressor such as the sight of blood, it may trigger your nervous system to slow down and your heart to dilate your blood vessels — both of which contribute to decreasing your blood pressure. This is also known as the vasovagal reflex. If your blood pressure becomes sufficiently low, you will not be able to maintain perfusion of your brain and you will faint. In some people, this fainting response can also result from situational triggers such as urination or coughing.

Can you faint from not eating?

Yes, if you do not eat for an extended period of time, your blood sugar will decrease (hypoglycemia). If it becomes sufficiently low, your brain will no longer have enough energy to maintain consciousness. If you are not eating due to nausea, you may also be drinking less fluids and become dehydrated — which predisposes you to fainting.

How do you stop yourself from fainting?

There's a number of ways to decrease your fainting episodes depending on the underlying cause. Always keep yourself well hydrated. If you feel lightheaded, consider lying down and elevating your legs such that they are above the level of your head. If you faint in response to specific triggers such as the sight of blood, avoid those triggers if possible.

Questions Your Doctor May Ask About Fainting

  • Q.How long were you unconscious?
  • Q.Do you notice your heart beating hard, rapidly, or irregularly (also called palpitations)?
  • Q.Have you been experiencing dizziness?
  • Q.Were you confused and disoriented when you woke up?

If you've answered yes to one or more of these questions, try our fainting symptom checker to find out more.

Fainting Quiz

Fainting Symptom Checker Statistics

  • People who have experienced fainting have also experienced:

    • 6% Dizziness
    • 6% Fatigue
    • 6% Nausea
  • People who have experienced fainting were most often matched with:

    • 63% Stroke or Tia (Transient Ischemic Attack)
    • 18% Orthostatic Syncope (Fainting)
    • 18% Vasovagal Syncope
  • Source: Aggregated and anonymized results from visits to the Buoy AI health assistant (check it out by clicking on “Take Quiz”).

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