A Serious Look at Fainting

Fainting is also called syncope. It's a brief loss of consciousness. It lasts just a minute or two, followed by a quick complete recovery. This is typically linked with a loss of postural tone that leads to falling down or needing to lie down. In an otherwise healthy person, fainting may not be cause for alarm. But in rare cases, it can be a sign of a serious underlying health condition. Syncope is usually caused by a sudden drop in blood pressure or heart rate that causes decreased blood flow to the brain. Before fainting, you may have sweaty palms, dizziness, lightheadedness, problems seeing, or nausea. 

In young people, the problem usually has no serious cause, though falls related to fainting can lead to injury. But in some cases, it can be due to an underlying heart problem that is more concerning. Triggers include:

  • Severe stress

  • Fear or other strong emotions

  • Standing for a long time

  • Suddenly standing up

  • Coughing very hard

  • Dehydration or loss of body fluid

  • Overheating

  • Very rarely, stimulants, such as caffeine

Fainting in an older person, a person with heart disease, or during exertion, or while lying down can be a cause for concern. In any of these cases you should call your healthcare provider. It's important to try to diagnose the cause of the fainting. Finding the cause may be difficult if the fainting was a one-time event.

Serious causes include:

  • Fast or slow abnormal heart rhythms

  • Coronary artery disease

  • Severe heart valve disease

  • Blood clot in the lung (pulmonary embolism)

  • Low red blood cell count (anemia) or blood loss

  • Medicine side effects

  • Dehydration, although this is not very common 

Most people who faint stay out a few seconds to less than a minute. If the person is unconscious for a longer time, call 911.Always let your healthcare provider know if you fainted.

Common tests for diagnosis

To find out if the cause of your fainting is serious, your healthcare provider will ask you questions about how often you faint, how long they last, and the events surrounding the episodes. Depending on the circumstances surrounding these episodes, your provider may order the following tests:

  • Electrocardiogram (ECG). This gives information about your heart rhythm and heart rate.

  • Echocardiogram (echo). This shows the structure of your heart, including the valves.

  • Orthostatic vital signs. This is where your heart rate and blood pressure are measured while you are lying, sitting, and standing. This is to see whether there is a change related to body position.

  • Tilt table testing. With this test you are strapped to a table while lying flat and then steadily brought to a standing position. Your blood pressure and heart rate are measured often to assess for changes. You may be given medicine to provoke these changes. The overall purpose of the test is to try to reproduce your fainting and assess if it's accompanied by a sudden drop in blood pressure or heart rate.

  • Ambulatory heart monitor or implantable loop recorder. If your healthcare provider thinks that the cause of your syncope may be related to your heart rhythm, they may have you wear a heart monitor for up to 4 weeks or recommend implanting a loop recorder underneath your skin to keep track of your heart rhythm long-term.

Other tests that may be done but are less common are stress testing, computerized tomography (CT) scan, and magnetic resonance imaging) (MRI).

What to do

  • Try to find out what things can make you faint. 

  • Ask your healthcare provider what you can do to prevent fainting. For example, your provider may suggest that you: 

    • Get up slowly if you have been sitting or lying down for a long period of time. Exercising your legs while standing for long periods may help keep your blood moving.

    • Have food or liquids containing salt, such as crackers, pretzels, or a sports drink. Salt will raise blood pressure, making a sudden drop less likely. But added salt isn't good for many people who have high blood pressure. So ask your provider before increasing your salt intake.

    • Wear compression stockings

  • If you feel like you are going to faint:

    • Make sure you're in a safe place, then sit down right away so you don't fall and injure yourself.

    • Lie down after you've safely reached a sitting position. Prop your feet up on some pillows or a jacket so that your feet are above the level of your heart. This raises blood flow to the heart and in turn the brain. This is exactly what you need.

    • If you can't lie down, place your head between your knees to increase circulation to your brain.

    • Turn onto your side to prevent choking if you feel nauseous.

  • If you do faint, remain lying down for 10 or 15 minutes once you wake up. Check to see if you have a significant injury, such as a bump on your head or a hip injury. Also try moving your legs and then get up slowly.

  • Don't drive until your healthcare provider feels that it is safe to resume.

Online Medical Reviewer: Ronald Karlin MD
Online Medical Reviewer: Stacey Wojcik MBA BSN RN
Online Medical Reviewer: Steven Kang MD
Date Last Reviewed: 4/1/2023
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