Fainting can be scary, but it's often harmless.
Known medically as syncope, fainting happens when there’s not enough blood flow to the brain, causing a brief loss of consciousness.
But how do you know if it's just a simple faint or something more serious? Dr. Elijah Behr, a cardiologist at Mayo Clinic Healthcare in London, shares five key facts about fainting: what causes it, how to prevent it and when to see a doctor.
Most fainting is harmless, but not always
The most common type of fainting is vasovagal syncope, often triggered by emotional stress, pain, illness or dehydration.
"In some people, if they have a drop in blood pressure from emotional distress, pain, illness or dehydration, for example, or just generally have a low blood pressure, any provocation causes a reflex in the heart," Dr. Behr explained in a news release.
"Rather than the heart speeding up and pumping more forcefully to maintain the blood pressure, it starts to slow down. The blood pressure drops, the heart rate slows further, and the heart can pause for many seconds; sometimes close to a minute for some people who have more severe fainting episodes."
While simple fainting usually resolves quickly, cardiac syncope -- caused by an underlying heart problem -- can be more serious.
"This is usually a more abrupt loss and return of consciousness than in simple fainting. If you're older, you're more likely to have underlying heart disease that you may or may not be aware of. That's one of the reasons to be more concerned about loss of consciousness in older individuals," Behr explained.
"Young people can also have heart diseases that can cause cardiac syncope that may be a warning sign of something more serious to come, so it is important to investigate it."
Warning signs
Fainting often comes with early warning signs:
Lightheadedness
Nausea
Buzzing in the ears
Tunnel vision or temporary vision loss
Sweating and clamminess
Some people get these warnings 30 minutes before fainting, while others have just 30 seconds to react, Behr added.
What to do if you feel faint
"If your blood pressure is getting low and you're getting those symptoms, it means the blood doesn't get into your brain, and if your heart is trying to push the blood to your brain against gravity, then it's struggling. You really need to get your head level or below your heart so the blood pressure gets back to the brain, and that will avert all the symptoms and the vicious cycle that ensues," Behr explained.
"Get your head between your knees or lie down and put your head down and your feet up in the air, depending on where you are and what is feasible to do."
Key steps if you or someone else faints:
Check for breathing and a pulse. If absent, start CPR and call for help
Lay the person flat and open the airway
Rest after fainting and drink water, preferably with electrolytes if dehydrated
Getting up and walking around straight away is probably the worst thing to do, Behr warned.
When to see a doc
Most simple fainting doesn’t require emergency care.
"If somebody has had simple fainting with the clear precipitants that I described, it is best to have a chat with your GP (your primary care physician) to talk about it. Particularly if it's a first onset of symptoms, it's best not to ignore it," Behr added.
"Often people go to the emergency department after a first faint, which I think is very fair to do and I would encourage."
Seek medical help if:
You faint while exercising
You have heart palpitations
There’s a family history of sudden death or heart problems
You faint without warning or get injured during a fall
Can fainting be prevented?
"For general preventive measures, we advise most people who have fainted to drink more water and to sometimes add a bit of salt to their food, because generally they're running a low blood pressure," Behr said.
"For those who faint at the sight of blood, cognitive behavioral therapy (CBT) may help overcome the reaction," Behr also added.
More information
The Cleveland Clinic has more on causes and first aid tips for fainting.
SOURCE: Mayo Clinic, news release, Feb. 18, 2025
