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Home > Health Library > Fainting
Fainting is a sudden, brief loss of consciousness. When people faint, or pass out, they usually fall down. After they are lying down, most people will recover quickly.
The term doctors use for fainting is syncope (say "SING-kuh-pee").
Fainting one time is usually nothing to worry about. But it is a good idea to see your doctor, because fainting could have a serious cause.
Fainting is caused by a drop in blood flow to the brain. After you lose consciousness and fall or lie down, more blood can flow to your brain so you wake up again.
Most causes of fainting are usually not signs of a more serious illness. In these cases, you faint because of:
Fainting caused by the vasovagal reflex is often easy to predict. It happens to some people every time they have to get a shot or they see blood. Some people know they are going to faint because they have symptoms beforehand, such as feeling weak, nauseated, hot, or dizzy. After they wake up, they may feel confused, dizzy, or ill for a while.
Some causes of fainting can be serious. These include:
Sometimes the cause is unknown.
Fainting may be the sign of a serious problem if:
To find the cause of fainting, a doctor will do a physical exam and ask questions about the fainting episode. You can help your doctor by being prepared to describe what happened before you fainted, how long you were "out," and how you felt when you woke up.
Depending on what the physical exam shows, the doctor may want to do tests. These tests may include:
If you know you tend to faint at certain times (such as when you get a shot or have blood drawn), it may help to:
You may need to see a doctor if you have ongoing dizziness or fainting.
Other Works Consulted
Shen W-K, et al. (2017). 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope. Circulation, published online March 9, 2017. DOI: 10.1161/CIR.0000000000000499. Accessed March 30, 2017.
Current as ofSeptember 23, 2018
Author: Healthwise StaffMedical Review: William H. Blahd, Jr., MD, FACEP - Emergency MedicineAdam Husney, MD - Family MedicineKathleen Romito, MD - Family MedicineElizabeth T. Russo, MD - Internal Medicine
Current as of:
September 23, 2018
Medical Review:William H. Blahd, Jr., MD, FACEP - Emergency Medicine & Adam Husney, MD - Family Medicine & Kathleen Romito, MD - Family Medicine & Elizabeth T. Russo, MD - Internal Medicine
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