Syncope (Fainting)

What is syncope?

Syncope (the medical term for fainting) is when a person briefly passes out but then wakes up relatively quickly. Some people fall when they faint, but others may notice warning signs, such as dizziness, in time to sit or lie down. Syncope can happen when the brain doesn’t get enough blood for a short time. It usually only lasts for a few minutes before people slowly return to normal. 

Syncope is not a disease but a symptom with many possible causes. Most fainting is related to temporary drops in blood pressure and is not serious. Less commonly, heart rhythm problems or other medical conditions can cause syncope. Seeing a doctor can help determine the cause.

Types of syncope

Cardiac syncope

Cardiac syncope is fainting caused by a heart problem that affects blood flow to the brain. It only accounts for about 1 in 10 cases of syncope but can reflect a serious heart condition such as an unusual heart rhythm or damage to the heart. Warning signs of cardiac syncope can include chest pain, sudden changes in heart rate, or fainting during exercise. This type of fainting is serious and needs immediate medical care.

Reflex syncope 

Reflex syncope (sometimes called vasovagal syncope) is the most common cause of fainting. It happens when the body overreacts to a specific trigger or situation, such as fear, pain, standing too long, dehydration, or donating blood. This reaction can cause blood pressure to drop and sometimes slow the heart, reducing blood flow to the brain and causing people to faint.

Reflex syncope is a brief, automatic reflex and does not mean the heart or brain is damaged. Reflex syncope can also happen during specific situations, such as coughing, laughing, urinating, or putting pressure on the neck.

Orthostatic syncope 

Orthostatic syncope happens when a person’s blood pressure drops after they change position, like going from sitting or lying down to standing up. Orthostatic syncope can happen in certain situations, such as when a person is dehydrated or taking certain medicines or as a symptom of other health conditions, such as Parkinson’s disease.

Other causes of syncope

Some people have health conditions that affect how the body responds to standing, such as postural orthostatic tachycardia syndrome (POTS). A doctor can help determine whether this may be a cause of syncope.

Symptoms of syncope

Knowing the warning signs of fainting can help prevent falls. Before fainting, people may notice:

• Dizziness
• Lightheadedness
• An urge to vomit
• Vision that becomes blurry or blacks out
• Cold or clammy skin

Who is more likely to experience syncope?

Anyone can faint, even people with no other health conditions, but syncope is more common in older adults. People with heart disease or conditions that affect blood pressure (such as Parkinson’s disease) may be at higher risk and should talk with a doctor if they faint.

How is syncope diagnosed and treated?

Diagnosing the causes of syncope

After a person faints, a doctor asks questions about what happened before and after the episode. They will also perform tests to try to find the cause of a person’s syncope. Because fainting can sometimes be related to heart problems, doctors may run tests to check the heart, such as an electrocardiogram (EKG). Other tests, like a tilt table test, help show how heart rate and blood pressure change when a person moves from lying down to standing.

Learn more about neurological diagnostic tests and procedures.

Treating syncope and its causes

Once a person understands why they might faint, they can take steps to prevent it, like staying hydrated or avoiding known triggers.

If a person feels like they are about to faint, they can take steps to prevent it from happening:

• Make a fist
• Cross legs
• Squeeze thighs together
• Tighten arm muscles
• Sit down and lean forward with head between the legs

If a person faints, check that they are still breathing. When the person wakes up, they should lie down for 10 to 15 minutes in a cool, quiet area. If this isn’t possible, they should sit with their head between their knees. Sipping on cold water can also help people recover after fainting. Most people recover within a few minutes or hours of an episode.

People who are at serious risk for syncope due to underlying heart or other medical conditions may need treatment to protect them from fainting. For example, a person with cardiac syncope may receive a pacemaker to help regulate their heartbeat.

What are the latest updates on syncope?

The National Institutes of Health (NIH), which includes NINDS, is the leading federal funder of research on the brain and nervous system. NIH supports new research to better understand, diagnose, and treat disorders associated with syncope.

For more information on research about syncope, check NIH RePORTER, a searchable database of current and past research projects funded by NIH and other federal agencies. RePORTER also has links to publications and resources from these projects. 

For research articles and summaries on syncope, search PubMed, which contains citations from medical journals and other sites.

How can I or a loved one help improve care for people with syncope?

Consider participating in a clinical trial so clinicians and scientists can learn more about syncope and related disorders. Clinical research with human study participants helps researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.

All types of volunteers are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities. This helps make sure that study results apply to as many people as possible and that treatments will be safe and effective for everyone who will use them.

For information about participating in clinical research visit the NINDS Clinical Trials site and NIH Clinical Research Trials and You. Learn about clinical trials currently looking for people with syncope at ClinicalTrials.gov, a searchable database of current and past clinical studies and research results.

Learn about related topics

• Postural Orthostatic Tachycardia Syndrome (POTS)
• Parkinson’s Disease