About Unexplained Fainting

Some causes of unexplained fainting are harmless, or can be addressed with simple lifestyle changes. Others can be more serious. A monitoring device may help your doctor rule in or rule out if an abnormal heart rhythm is causing you to faint.


Fainting, also called syncope (SING-ko-pee), is a sudden loss of consciousness. It occurs when the blood pressure drops and not enough oxygen reaches the brain. There are times when fainting may look like a seizure.


People faint for many reasons, including:

  • Standing too fast
  • Exhaustion
  • Emotional upset and/or stress
  • Overheating
  • Abnormal heart rhythms
  • Illness or some medications

Some causes of fainting are not easy to explain, and some causes of unexplained fainting can be life-threatening. Whether you have isolated unexplained fainting spells or you repeatedly faint, you should seek the help of a doctor.


Usually fainting occurs while standing. It may happen suddenly or may be preceded by a sensation of:

  • Lightheadedness
  • Warmth or sweaty palms
  • Nausea
  • Fading of vision

If you faint during exercise or experience dizziness, heart palpitations, or seizure-like episodes, you should see a doctor.

Risk Factors

While some causes of unexplained fainting are harmless, others may be serious. Heart-related causes, including abnormal heart rhythms, are among the most serious causes of fainting. Also, if you do not have any warning signs before you faint, you may fall unexpectedly and be injured.


A correct diagnosis of infrequent but recurring fainting starts with gathering the facts about your own fainting spells. Your doctor or team of doctors may take a medical and family history and perform a physical exam. If your doctor suspects a heart condition is causing your fainting, diagnostic tests may be run to gather information about your heart.

Information on this site should not be used as a substitute for talking with your doctor. Always talk with your doctor about diagnosis and treatment information.

Last updated: 27 Sep 2010

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