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.

A.I. Health Assistant

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

Take a quiz

8 Potential Fainting Causes

Disclaimer: The article does not replace an evaluation by a physician. Information on this page is provided as an information resource only, and is not to be used or relied on for any diagnostic or treatment purposes.

  1. 1.Concussion (Mild Traumatic Brain Injury) Needing Imaging

    Mild traumatic brain injury requiring imaging is defined as being fairly responsive after an injury to the head but with enough warning signs that a picture of the inside of the skull needs to be taken.

    Mild traumatic brain injuries have good outcomes if seen early enough by doctors. Delay can be dangerous.

    Rarity:
    Common
    Top Symptoms:
    nausea or vomiting, dizziness, difficulty concentrating, sensitivity to light, frequent mood swings
    Symptoms that always occur with concussion (mild traumatic brain injury) needing imaging:
    head or face injury
    Urgency:
    Hospital emergency room
  2. 2.Atrial Fibrillation

    An arrhythmia is a problem with the speed or rhythm of the heartbeat. The atria comprise two out of the four chambers of the heart. When their beat is disturbed, symptoms such as a racing heart, chest pain, breathlessness, and dizziness may occur.

    More than 1/2 of people with short term atrial fibrillation get their normal heart rhythm back in less than 2 days without any treatment.

    Rarity:
    Common
    Top Symptoms:
    fatigue, shortness of breath, chest pain, racing heart beat, shortness of breath on exertion
    Urgency:
    Emergency medical service
  3. 3.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
  4. 4.Pulmonary Embolism

    A pulmonary embolism is a sudden blockage in an artery in the lungs. It is a serious condition that can cause permanent damage to the affected lung, low oxygen levels in your blood, or damage to other organs in your body from not getting enough oxygen.

    A pulmonary embolism is life-threatening. Recovery depends on treatment.

    Rarity:
    Uncommon
    Top Symptoms:
    shortness of breath, cough, rib pain that gets worse when breathing, coughing, sneezing, or laughing, fever, wheezing
    Urgency:
    Emergency medical service

    Fainting Checker

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

    Take a quiz
  5. 5.Intracerebral Hemorrhage

    Intracerebral hemorrhage occurs when a diseased blood vessel within the brain bursts, allowing blood to leak inside the brain. (The name means within the cerebrum or brain).

    Serious life-threatening condition with a high chance of death. Consultation with a brain specialist (neurosurgeon) is needed to determine outlook.

    Rarity:
    Rare
    Top Symptoms:
    nausea, new headache, severe headache, vomiting, stiff neck
    Urgency:
    Emergency medical service
  6. 6.Atrial Fibrillation

    An arrhythmia is a problem with the speed or rhythm of the heartbeat. The atria comprise two out of the four chambers of the heart. When their beat is disturbed, symptoms such as a racing heart, chest pain, breathlessness, and dizziness may occur.

    More than 1/2 of people with short term atrial fibrillation get their normal heart rhythm back in less than 2 days without any treatment.

    Rarity:
    Rare
    Top Symptoms:
    fatigue, chest pain, shortness of breath, racing heart beat, lightheadedness
    Urgency:
    Emergency medical service
  7. 7.Subarachnoid Hemorrhage

    Subarachnoid hemorrhage is bleeding in the area between the brain and the thin tissues that cover the brain. It's typically caused by a ruptured aneurysm (out-pouching of an artery's wall).

    Indefinite

    Rarity:
    Rare
    Top Symptoms:
    new headache, being severely ill, nausea or vomiting, severe headache, vision changes
    Symptoms that always occur with subarachnoid hemorrhage:
    new headache, being severely ill
    Urgency:
    Emergency medical service
  8. 8.Abdominal Aortic Aneurism (Aaa) Rupture

    The aorta is the major blood highway. Injuries to the aorta can cause life-threatening internal bleeding.

    An aortic injury must be treated immediately with emergency surgery. The prognosis depends on how quickly you are transported to an operating room.Recovery time is dependent on the type of surgery. Open-abdominal surgery involves replacement of the damaged section of the aorta by a synthetic tube (graft), which is sewn in place with an open-abdomen approach. It takes a month or more for full recovery. Endovascular surgery is a less invasive procedure, where the synthetic graft is threaded up to the damaged section through an artery in the leg. Recovery time is shorter, but follow-up appointments will be more frequent, as it will be important to monitor for any leaking of the graft.

    Rarity:
    Rare
    Top Symptoms:
    being severely ill, nausea, severe abdominal pain, side pain, spontaneous back pain
    Symptoms that always occur with abdominal aortic aneurism (aaa) rupture:
    being severely ill
    Urgency:
    Emergency medical service

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.If this interview is about someone else, or "myself" is selected by accident, it is very important for us not to miss this question: has the person regained consciousness?
  • Q.Have you been feeling more tired than usual, lethargic or fatigued despite sleeping a normal amount?
  • Q.How long were you unconscious?
  • Q.Do you notice your heart beating hard, rapidly, or irregularly (also called palpitations)?

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

Take a quiz

Fainting Symptom Checker Statistics

  • People who have experienced fainting have also experienced:

    • 7% Dizziness
    • 6% Fatigue
    • 5% Nausea
  • People who have experienced fainting were most often matched with:

    • 2% Concussion (Mild Traumatic Brain Injury) Needing Imaging
    • 1% Atrial Fibrillation
  • Source: Aggregated and anonymized results from visits to the Buoy AI health assistant (check it out by clicking on “Take Quiz”).

A.I. Health Assistant

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

Take a quiz