Fainting is a loss of consciousness that happens quickly and sometimes without warning. A fainting episode usually resolves within seconds to minutes. If fainting is caused by another condition, then the condition will need to be treated.
In general, fainting is caused by decreased blood flow to the brain.
Blood Flow to the Brain
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Decreased blood flow to the brain can be caused by:
Most commonly, vasovagal spells. Vasovagal spells can occur:
- During medical procedures
- During times of high stress, trauma, or fright
- After standing still for a long period of time
- Orthostatic hypotension, low blood pressure when standing
- Hypoglycemia, which is low blood sugar
- Stroke or transient ischemic attack
- Abnormal heart rhythms
- Heart conditions
- Blood loss
Fainting can also occur as a side effect to medications. These include:
- Blood pressure medications
- Medications to regulate heart rhythms
- Certain antidepressants
Last reviewedMarch 2014by Rimas Lukas, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.