Cedars-Sinai Blog

Fainting vs. Seizure: How to Tell the Difference

loss of consciousness, seizure, fainting, blackout, causes

Ever had an experience where you or someone you were with blacked out and woke up with no idea what happened? 

When someone loses consciousness, doctors usually ask the patient to walk them through what they experienced immediately before the episode. 

"Usually the recollection of the event, either from the patient or a bystander, helps offer clues about whether they've experienced a seizure or a fainting episode," says Dr. Jeffrey M. Chung, a neurologist and director of the Cedars-Sinai Epilepsy Program.

To function optimally, the brain requires oxygen and electrical signals. The oxygen comes from the heart pumping blood to the brain while electrical signals come from the cells as they move electrolytes around.

Both seizures and syncope, the medical name for fainting, are your brain's way of telling you one of these processes isn't working properly. 


Why they happen: Seizures happen when there's a disturbance in the normal electrical activity in the brain. An estimated 10% of people experience an unprovoked seizure during their lifetime—and when it happens, it can be terrifying. 

What they look like: Seizures can look different depending on which part of the brain is affected. 

You may or may not lose consciousness. You might shake violently or stare into space unable to recognize your own name. 

And while the symptoms can last for a full minute or more, you'll probably have no memory of the experience. 

What you should you do: If you see someone experiencing a seizure, get them to the floor if they aren't already lying down and move hard and sharp objects away from them.

Don't put anything in their mouths.

Don't attempt to restrain them or hold them down, but instead wait for the seizure to end. Then make sure a medical professional evaluates them. 


Why it happens: Sudden loss of consciousness, or syncope, happens when there isn't sufficient blood flow to the brain—and the experience is fairly common. Half of all people will faint at least once during their lifetime. 

Syncope can happen as a random, isolated event, or it can happen frequently over a period of time. 

"Some causes of fainting are harmless. Others can be life-threatening," explains Dr. Joel M. Geiderman, co-chair of Emergency Medicine at Cedars-Sinai.

In younger people, the causes tend to be more benign. Maybe they haven't eaten or they're dehydrated. In older people, fainting is sometimes  a sign cardiac issues, such as atrial fibrillation.

What you should do: While you may recover quickly and fully from a fainting spell, you should always tell your doctor about the episode. 

"It could be a sign of an underlying heart problem, so it's important to visit a health professional for a proper diagnosis and appropriate treatment plan," Dr. Chung says.

If you feel faint, lie down, or if you're sitting, place your head between your knees. 

If you see someone else faint, place the person face up and raise their legs above their heart level. If the person doesn't "come to" within 1 minute, call 911.

Seizure vs. fainting
Seizure specifics
Fainting specifics
Get it under control

Determining the underlying cause of fainting or a seizure usually requires a visit to your doctor, who will likely do cardiac and neurological tests.

"It may be nothing, but it may be something. In either case, it's always best to get to the bottom of it," Dr. Chung says.