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About Unexplained Fainting

Fainting (Unexplained)

Some causes of unexplained fainting are harmless, or can be addressed with simple lifestyle changes. Others are more serious. An insertable cardiac monitor (ICM), also known as an insertable loop recorder (ILR), may help your doctor determine 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:

  • Changes in blood pressure
  • Changes in heart rate
  • Abnormal heart rhythms
  • Anaemia (an inadequate quantity of healthy red blood cells to carry adequate oxygen to your tissues)
  • Poor blood circulation
  • Metabolic and lung disorders
  • Standing too fast
  • Exhaustion
  • Emotional stress
  • Pain
  • Overheating
  • Illness
  • Some medications

Some causes of unexplained fainting can be life threatening. Whether you have one unexplained fainting spell or if 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:

  • Light headedness
  • Falling for no reason
  • Warm or sweaty palms
  • Nausea
  • Fading of vision

These symptoms are sometimes referred to as pre-syncope if you experience them prior to a fainting episode. 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.


If you have syncope, it’s important to find out why you’re fainting. 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.

Questions and Answers

You may have many questions about your unexplained fainting spells. While many of your questions may be answered here, remember to talk with your doctor about anything more you'd like to know.


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.