Fainting, or passing out, is referred to medically as a syncopal episode or syncope. They’re typically triggered by a sudden, temporary drop in blood flow to the brain, leading to loss of consciousness and muscle control.

In a syncopal episode, the person falls down or over, which allows blood flow to return to the brain. Returning blood flow allows the person to regain consciousness.

Syncope is more common than you might think. It can happen at any age, including childhood, though fainting happens more frequently to people as they get older. Syncopal episodes usually last only seconds or minutes. They may be accompanied by temporary feelings of confusion when you regain consciousness.

Syncope can be caused by an underlying medical condition or from environmental triggers. Fainting can also result from an emotional response to a very difficult situation. Intense pain, low blood sugar, or a change in blood volume may also cause syncope. If you experience a drop in blood pressure or heart rate, you might faint abruptly.

Common causes of syncope include:

  • low blood pressure or dilated blood vessels
  • irregular heart beat
  • abrupt changes in posture, such as standing up too quickly, which can cause blood to pool in the feet or legs
  • standing for long periods of time
  • extreme pain or fear
  • extreme stress
  • pregnancy
  • dehydration
  • exhaustion

Some people faint at the sight of blood. Syncope can also be triggered by multiple factors, such as if you are dehydrated and have low blood sugar. Combined, those two things could make you faint, even if you wouldn’t have fainted from only one or the other.

Syncopal episodes are often preceded by warning signs or symptoms. These may include:

  • nausea
  • slurred speech
  • weak pulse
  • changes in body temperature that make you feel suddenly flushed or chilled
  • sudden, clammy sweat
  • pale skin
  • disturbances to your vision, like seeing spots, tunnel vision, blurry vision, or dilated pupils
  • feeling as if sounds are suddenly very far away
  • lightheadedness, wooziness, or feeling as if your head and body are weightless
  • numbness
  • dizziness
  • vertigo, or a sensation that the room is moving
  • rapid heartbeat
  • body weakness
  • shakiness
  • headache

If you experience any warning signs and feel like you’re about to faint, stop what you’re doing and sit or lie down. Try to lower your body down to the ground and elevate your legs higher than your head. This helps support blood flow back to the brain and may be enough to prevent a syncopal episode. And if you do faint, sitting or lying down will also help you avoid injuries from falling, such as hitting your head.

If the feeling doesn’t pass or if you repeatedly feel like you may faint, call your doctor. They can help determine next steps. If your doctor asks you to come to their office, have someone else drive you. Operating a motor vehicle when you feel faint is extremely dangerous.

Helping others

If you’re concerned that someone in your surroundings might faint, help them to sit or lie down. Loosen tight garments which might obstruct breathing, such as a neck scarf or tie.

If a person faints in your presence and doesn’t regain consciousness within one to two minutes, call your local emergency medical services. While you’re waiting for help to arrive, gently roll the person onto their side. Check to make sure they’re breathing. Don’t leave them alone, and make sure they are protected until help arrives.

If your fainting was caused by an identifiable trigger, such as extreme heat, make sure to avoid that trigger if possible. If blood pooling in your feet or legs is a concern, flex and exercise your feet. You may also benefit from compression socks.

You should also drink plenty of fluids following an episode and avoid stressful situations.

Fainting is not usually evidence of a serious condition, but it’s a good idea to let your doctor know if you’ve fainted. Call their office right away. They will let you know if you should be seen immediately.

Make sure to see a doctor if:

  • you’ve fainted more than once
  • it took longer than two minutes for you to regain consciousness
  • you suspect you are pregnant
  • you lost control of your bladder or bowels when you fainted
  • you have a pounding or irregular heartbeat
  • you have chest pain
  • you have a history of heart disease, high or low blood pressure, or diabetes

When you visit your doctor, they will do a physical exam and may do several tests. These tests may include:

  • blood pressure reading
  • pregnancy test, if there’s a chance you may be pregnant
  • electrocardiogram (EKG), to analyze your heart’s electrical activity and to check for an irregular heartbeat
  • tilt table test, to analyze how your heart and blood pressure respond to differences in posture

The doctor may also ask for your medical history, which includes:

  • current and past diagnoses
  • an account of what happened during the event
  • medication use, both over-the-counter and prescription

You’ll be asked to recall the incident in as much detail as possible. This will help your doctor identify any triggers, such as extreme heat or stress, that may have played a role. If you don’t remember fainting but someone else who was there can supply this information, have them come with you to your appointment. They may also write down their thoughts about what happened for you to bring with you to your doctor’s office.

Syncope is usually not serious, but ruling out a medical cause is important. Fainting may also be a sign that you need to reduce your stress or pay more attention to food or fluid intake.

Learn more: 10 simple ways to relieve stress »

Fainting is common. Remember, if you feel like you will faint, follow these tips:

  • Try to remain calm and to control your breathing.
  • Sit down with your head between your legs, or lie down with your legs elevated.
  • Call your doctor if you lost consciousness.

If you regularly feel faint, make notes each time about what happened leading up to that feeling. It could be something that you can easily change, like eating more regularly or staying hydrated, or it could be caused by something that you need your doctor’s help to identify, like low blood pressure. Even if you think you’ve identified your triggers, it’s important to let your doctor know how you’ve been feeling.