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A to Z Symptoms: Fainting

A to Z Symptom: Fainting

May also be called: Syncope; Swooning; Passing Out

More to Know

In most cases, fainting — or syncope (SIN-ko-pee) — is not a sign of a dangerous problem.


Fainting happens when not enough oxygen reaches the brain due to a fall in blood pressure. Common causes include dehydration, a quick change in position, standing or sitting still for a long period, becoming overheated, hyperventilation (overbreathing), low blood sugar, anemia, sudden fear of something (for example, the sight of blood), and some heart problems.

Most cases have warning signs (such as a change in vision, dizziness, nausea, or stomach pain) that happen a few seconds before passing out.


Fainting in children, especially teens, is common but shouldn't be ignored. Discuss it with your doctor, especially if it occurs during exertion (exercising, running, etc.) or happens often. Fainting that's related to a heart problem often occurs during exercise and without warning and can include feelings of chest pain or the heart racing.

Fainting not related to the heart often can be prevented by drinking more liquids to increase the total amount of fluid in the bloodstream. Also, caffeine should be avoided. Sometimes, a doctor might recommend increasing salt in the diet as long as blood pressure is not borderline-high or high.

Keep in Mind

When warning signs of fainting occur, quickly sitting down, dropping the head between the knees, or lying down on the floor may help avoid a loss of consciousness. Then, gradually get up after the dizzy feeling has passed.

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.

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Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.
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