Fainting or "blacking out", medically known as syncope, is a momentary loss of consciousness, often followed by a fall

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Why do we faint?

Fainting can happen for a number of reasons, but it's usually related to a sudden drop in blood pressure or an abrupt and abnormal increase or slowing of your heart rate. These lead to a reduction in oxygen-rich blood flowing to your brain. This can be caused by an underlying heart problem.

Need to know

Just before fainting, you may experience some warning signs, such as feeling hot, weak or nauseous. You may also feel dizzy, experience blurred vision or have difficulty hearing just prior to passing out. Other common warning symptoms include:

  • a cold sweat
  • ringing in your ears
  • confusion
  • palpitations

An episode of fainting can sometimes be triggered by certain medications, standing too quickly or for too long, pain or emotional stress. The loss of consciousness associated with fainting is usually very brief, but will cause you to collapse if you're standing at the time.

Fainting may not be a sign of anything serious. However, if you've been fainting frequently, have chest pains, are pregnant or have a family history of heart disease, your GP or consultant may want to investigate the potential underlying cause.

If they suspect you may have a heart problem, you might have an electrocardiogram to monitor your heart's rhythm and electrical activity, and a Holter monitor which you wear to record your heart’s rhythm over up to several days. A tilt-table test might be recommended if your fainting episodes seem to be related to a change in blood pressure when you sit or stand.

Treatment options for fainting will depend on the type you've been experiencing. Your consultant will discuss your options with you and in many cases, no treatment is needed. If an underlying cause of fainting is found, treating it should help prevent further episodes.

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This content is intended for general information only and does not replace the need for personal advice from a qualified health professional.