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Common Causes of Fainting

Know when to call the doctor or go to the ER.
An illustration of a woman lying on the ground on her side. One leg is bent up and her arms are bent as well, showing a position that represents a recent fall. An oval and starts surround her head showing dizziness. She has medium brown skin, short, curly, dark brown hair and is wearing a medium blue short-sleeved t-shirt and dark blue jeans with blue sneakers.
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Written by Andrew Le, MD.
Medically reviewed by
K Health - Telemedicine
Last updated September 20, 2021

Fainting quiz

Take a quiz to find out what's causing your fainting.

Fainting quiz

Take a quiz to find out what's causing your fainting.

Take fainting quiz

What is fainting?

Fainting causes a temporary loss of consciousness. It’s caused by decreased blood flow to the brain.

When people feel like they are going to faint, they can often sit down before they do. But some people fall when they faint, which can lead to an injury.

Typically, the cause is a minor issue. But sometimes it’s a sign of a serious condition.

If you were injured when you fainted, you probably did not have any warning signs. This may mean that the cause is more serious. You should see a doctor to treat the injury and to figure out why you fainted.

If you have recently fainted, make sure you stay seated or lying down for several minutes before you move. Sudden movements may cause you to faint again.

When you are able to move, move slowly from one position to the next. Wait a few minutes between each step (laying to sitting, then sitting to standing).

You may need to see a doctor or go to the ER. If you have recently fainted, do not drive yourself to the ER or to an urgent care without your doctor’s permission.

You may not remember what was happening just before you fainted or immediately after you awakened. Talk to anyone who may have seen you faint to find out what they noticed just before, during, and after the event. That information can help your doctor figure out the underlying cause.

Vasovagal syncope

Pro Tip

Ask your doctor: What tests should be done to determine what caused my fainting. What can be done to prevent this in the future? —Dr. Priyanka Gimbel

The most common cause of fainting, particularly in someone younger than age 50, is vasovagal syncope (syncope is the medical term for fainting). It is caused by abnormal reflexes that make the heart temporarily beat slowly and make the veins in your body widen. Your blood pressure briefly drops and your blood pools in the lower half of your body instead of going to your most important organs like the brain.

Signs that you may have vasovagal syncope include:

  • You usually feel lightheaded, nauseous, clammy or sweaty, or have tunnel vision and feel like you are about to faint. You usually have time to sit or lie down before you faint.
  • You fainted for a brief time in response to an intense emotion, such as the sight of blood, pain, or fear.
  • You fainted while going to the bathroom (urinating or having a bowel movement) or when coughing.

Vasovagal syncope is not an emergency. However, if it continues to happen, discuss with your doctor to see if there is anything you can do to help prevent them.

Other non-serious causes

A number of other causes for fainting are not considered serious. They include:

  • Dehydration.
  • A viral illness.
  • Certain medicines that affect blood pressure—such as blood pressure medicines, sedatives, certain antidepressants—may increase the tendency to faint. If you faint just after standing up suddenly from a sitting or lying position, it could be caused by medications (or dehydration).
  • Drinking excessive alcohol.


Dr. Rx

If you fainted and realized that you soiled yourself while you were unconscious and felt confused or tired after you regained consciousness, I would be concerned about a seizure. If this is the first time you’ve had a fainting episode like this, I would want to do blood work, an EEG (to evaluate your brain waves), and a brain scan. —Dr. Gimbel

A loss of consciousness can be caused by a seizure. This is a potentially serious issue.

During a seizure, your body may jerk uncontrollably for at least 30 seconds and often longer. The period that you’re unconscious is often longer than 1 to 2 minutes.

People who have a seizure may urinate or have a bowel movement while it is happening. They may bite their tongue. They are often confused and extremely weak for several hours after regaining consciousness.

Call 911 or have someone take you to the emergency room immediately if this is your first seizure.

If you have epilepsy or other conditions that can cause seizures, you should follow the treatment plan from your neurologist. If you do not have a treatment plan or are unsure of what to do, call your neurologist right away to see what they recommend.

Abnormal heart rhythms

A loss of consciousness can also be caused by abnormal heart rhythms. This is when there is a malfunction of the heart’s electrical system that regulates your heartbeat. It can be serious.

There are several different types of abnormal heart rhythms that can cause fainting, including sinus bradycardia, heart blocks, ventricular tachycardia, and supraventricular tachycardia, which result in very slow or very fast heart rates.

These can be mild to life-threatening. You may have a heart rhythm abnormality if:

  • You felt pain in your chest or palpitations before you fainted.
  • You fainted while you were lying or sitting, without changing your body position.
  • You fainted due to intense emotions.
  • You have a history of heart problems.

Abnormal heart rhythms can be treated with medications, implantable heart devices, or a minimally invasive procedure. It’s also important to control your other risk factors for heart disease.

Pro Tip

If you are on medications that make your blood pressure drop, they may need to be adjusted. Or you may just need to take more time between changing positions. If you have not been drinking enough fluids or have been drinking alcohol or caffeine, you might be dehydrated. which caused the fainting. —Dr. Gimbel

Other serious causes

There are a few other serious but less common causes of fainting. They include:

The more common symptoms of these conditions include chest pain, difficulty breathing, a fast or irregular heart rate, palpitations, or feeling lightheaded or dizzy.

If you are experiencing any of these symptoms and have recently fainted, or you have recently fainted and have a history of heart or lung problems, call 911 or have someone take you to the ER right away.

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The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
K Health - Telemedicine
Dr. Gimbel is a board-certified Family Medicine physician and writer/reviewer for Buoy Health. She received her undergraduate degree in Neuroscience with a minor in Sociology from the University of Illinois at Chicago (2008) and graduated from the University of Illinois at Chicago College of Medicine and School of Public Health (2013). She completed a family medicine residency at the University of...
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