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What’s behind fainting spells?

You break out into a cold sweat. Your heart pumps a little faster. Your stomach starts to turn—or churn. You see spots before your eyes. The next thing you remember, your head is between your knees—and you didn’t put it there.

You’ve had a fainting spell. How did it happen? And is it something you should worry about?

The brief loss of consciousness known as fainting, or syncope, occurs when the brain doesn’t get enough blood. This can happen for any number of reasons. Common culprits include:

  • a stress surge. You just got devastating news—or perhaps exhilarating news. Either way, sudden fright or excitement can bring on a fainting spell by affecting nerves that control blood pressure. Panic attacks can also cause a person to pass out.
  • your cardiovascular system. Serious reasons for reduced blood flow to the brain include an irregular heartbeat, a narrowed aortic valve or a narrowed carotid artery (found in the neck). But more often, simply standing up too fast can cause a drastic drop in blood pressure that prevents adequate circulation to the head.
  • dehydration. Dehydration contributes to low blood pressure by reducing fluid volume in the circulatory system. Avoid this by drinking plenty of liquids, especially before and during physical activity that takes place in hot, humid weather.
  • low blood sugar. Maybe you have diabetes or maybe you’ve gone a few too many hours without having eaten. In either case, plummeting blood sugar levels may cause you to feel faint.
  • certain medications (especially blood pressure medications), seizure disorders, heart attack, stroke and other conditions may also trigger a fainting spell.

While most episodes are temporary, harmless and insignificant, some may be a sign of a serious health problem. For that reason, fainting spells, especially ongoing ones, should be reported to your physician.

You can provide valuable assistance by preparing answers to these questions (you may need the help of a witness):

  • Are you more likely to faint at certain times or during specific activities?
  • How do you feel before you faint?
  • Does your face turn red or lose color?
  • Do you break out into a sweat?
  • How long do your spells last?
  • Have you ever lost bowel or bladder control during a spell?
  • Can you do something to prevent yourself from fainting?
  • How do you feel after you’ve fainted?