Skip to main content

What is syncope?

Syncope is a condition that occurs when there is a sudden decline in blood flow to your brain, leading to a temporary loss of consciousness. Syncope is commonly referred to as a fainting spell or passing out. Syncope affects all age groups and can occur in healthy people, but it happens more often in the elderly.


Typically, when you are about to faint, you will feel dizzy, lightheaded or nauseated. Your field of vision may “black out” or “white out.” Your skin may also feel cold and clammy to the touch. You will usually drop to the floor when losing consciousness. After fainting, you may be unconscious for a few minutes but will come to and then slowly return to normal.

There are several signs and symptoms that indicate an episode of syncope and may occur before losing consciousness:

  • Blurred vision
  • Confusion
  • Feeling warm or hot
  • Lightheadedness, dizziness or a floating feeling
  • Nausea
  • Sweating
  • Vomiting
  • Yawning

When to see a doctor

Syncope is not a life-threatening condition. However, more serious conditions can look like fainting and require immediate medical treatment. If you see someone lose consciousness, check to see if they are breathing. If they are not, call 911 and begin CPR.


Syncope has a variety of causes. Though some causes of syncope are a warning of a serious condition, it is most often a result of a benign situation. Common causes include:

  • Dehydration
  • Psychological triggers
  • Shock
  • Drugs or alcohol
  • Low blood pressure

An increased risk of syncope has been associated with certain classes of drugs, including angiotensin converting enzyme (ACE) inhibitors, alcohol, antihistamines, antipsychotics, calcium antagonists, diuretics, levodopa, narcotics, and nitrates. These can lower the blood pressure and/or make the brain more susceptible to passing out.

Types of syncope

  • Carotid sinus syncope—Caused by constriction of the carotid artery in the neck and can occur after turning the head while shaving, for example, or when wearing a tight collar.
  • Orthostatic syncope—Occurs when people with heart or vascular disorders stand up from lying down or sitting too quickly, and the heart or blood vessels cannot maintain blood flow to the brain.
  • Situational syncope—Happens during urination, defecation, coughing or as a result of gastrointestinal stimulation.
  • Vasovagal syncope—Usually has an easily identified triggering event, such as emotional stress, trauma, pain, the sight of blood or prolonged standing.

Types of treatment

Treatment after losing consciousness depends on the cause. This requires an evaluation of existing medical problems, recent activities or illnesses.

Go to top