The Facts About Fainting Spells

Fainting spell, passing out, swooning or syncope — whatever you call it, losing consciousness is unpleasant, distressing and disorienting. It’s also really common, occurring in about one-third of people at least once in their lives.

But is fainting hazardous? Are reasons for fainting serious?

Most of the time, the answer is no. In many cases, you can remedy straightforward causes like dehydration or avoid personal triggers like the sight of blood. Sometimes, stopping a medication with certain side effects is all that’s needed. Oftentimes, kids grow out of a tendency to faint.

However, fainting can be a real health concern, particularly when a cardiac condition like a dangerous arrhythmia is the underlying cause. In fact, fainting spells are sometimes the first warning for unsuspected heart disease. Below, experts lay out facts on fainting in adults and kids.

[SEE: 8 Ways to Stay Hydrated Besides Drinking Water.]

Common Experience

Fainting, or syncope, by definition means there’s a transient loss of consciousness. It’s usually caused by a brief drop in blood pressure, which prevents sufficient blood flow to your brain, causing you to lose consciousness.

Fainting is super-common. Between 20% and 30% of the population has fainted at some point in their lives, according to various estimates. “Syncope is probably the most common presentation for any symptom in the emergency department as a whole,” says Dr. Shamai Grossman, vice-chair of emergency medicine at Beth Israel Deaconess Medical Center and an associate professor of emergency medicine at Harvard Medical School. “It’s incredibly common — it represents 1% to 2% of all our visits.”

Vasovagal Syncope

Vasovagal and volume-related syncope are the most frequent presentations for fainting categories. The vagus nerve is responsible for regulating heart rate and respiratory rate, as well as some reflex actions such as coughing, sneezing, swallowing and vomiting. With vasovagal syncope, people pass out because of issues with the vagus nerve. Volume syncope refers to low blood volume, usually due to bleeding or dehydration.

Triggers for vasovagal fainting vary by individual. “There are a lot of people out there who have vasovagal hypersensitivity,” notes Grossman, who has done extensive research on fainting. Having blood drawn, simply seeing blood, hearing bad news, feeling pain, facing strong emotions or sudden shock can all serve as triggers. “There are people who pass out when they laugh too much,” he says. “There are people who pass out sitting on the toilet. All this has to do with vasovagal hypersensitivity.”

Episodes of fainting are usually brief. Part of the definition of syncope is that it’s transient, Grossman notes. Fainting episodes usually last less than a minute or two. “If it’s more than five minutes, they don’t call it syncope anymore,” he says.

Fainting often has warning signs. People may experience these symptoms a few seconds before fainting:

— Dizziness or lightheadedness.

— Sudden sweats or feeling cold.

— Vision changes like blurring or spotting.

— Nausea.

— Ringing in the ears.

— Ashy or pale appearance.

Rapid heart rate.

Taking preventive measures can help. Avoiding triggering scenarios may reduce syncopal episodes or consequences. For instance, if uncontrollable laughing makes you feel faint, it makes sense to stay away from comedy clubs. Safety can be an issue in some cases. “In certain situations, avoid driving a car or using heavy machinery,” Grossman says.

[Read: Do I Have Social Anxiety or Something Else?]

Fainting in Kids

Dehydration can result in fainting. Hot weather and too little fluid can combine to cause fainting, particularly in susceptible kids.

“Children and young adults are more prone to having vasovagal hypersensitivity,” says Dr. Emmanuelle Favilla, an attending physician with the division of cardiology at Children’s Hospital of Philadelphia. “In the summertime we don’t drink as much — kids are often caught up in what they’re doing. Dehydration is very common in the younger age group.” For kids who have a history of fainting, extra vigilance and supervision are a must around the pool or at the beach.

Simple steps can reduce fainting in susceptible kids. For their parents, Favilla says, “I usually recommend lifestyle interventions: good hydration, regular meals, adding a little salt to their diets so they can really hold onto the water they’re drinking.” Staying active is important, she adds: “A good exercise regimen keeps them conditioned.”

Breath-holding may cause fainting. “Little toddlers can have breath-holding spells when they get upset,” Favilla says. “That’s more of a behavior-type issue. Definitely, if they hold their breath long enough they can have a passing-out or syncopal issue. That’s usually seen in toddlers or preschool children.”

Many kids grow out of fainting. Teens go through a series of bodily and hormonal changes that can make them more vulnerable to fainting spells, Favilla notes. “And then, of course, the behavior of teenagers: They forget to drink or eat, or they don’t like to eat breakfast, so all those things can definitely make things worse in those age ranges.” Although there are exceptions, she says, “usually things get better once everything settles out after puberty and after changes in adolescent decision-making.”

Sudden Low Blood Pressure

Sudden low blood pressure from standing can make people faint. Orthostatic hypotension occurs when blood vessels don’t properly constrict after someone moves to an upright position from lying down or sitting. “People report standing up too fast, feeling lightheaded and just falling to the ground, or it can be when first getting out of bed,” Favilla says.

Careful rising may ease orthostatic episodes. When it comes to going from sitting to standing, “as you get older, your autonomic nervous system doesn’t quite auto-regulate the way it’s supposed to,” Grossman says. “One of the simplest fixes for older people: Get out of bed slowly and let the body have a little extra time to do that regulation.”

Certain medical conditions may cause fainting. Digestive tract disorders with gastrointestinal bleeding can lead to volume-related fainting. Postural orthostatic tachycardia syndrome, or POTS, is a blood circulation disorder involving low blood pressure with multiple symptoms including fainting.

[SEE: Signs of a Bad Heart: Don’t Overlook These Cardiac Symptoms.]

Cardiac Causes

Heart-related fainting is most concerning. “The third category — cardiac or heart-related causes of syncope — is the one we really get worried about, even though these are less common,” Grossman says. “Cardiac causes are potentially life-threatening.”

A cardiac evaluation may be needed. Heart tests vary depending on suspected conditions. An electrocardiogram, or EKG, is a typical test for patients who come to the ER for fainting. To diagnose or rule out cardiac conditions, doctors may order from a spectrum of tests including blood tests, a portable heart monitor, echocardiogram (echo or heart ultrasound), exercise stress test, tilt table test or cardiac MRI in the potentially most serious cases.

“I’m going to do a little digging on family history and exactly the details of the (fainting) episodes,” Favilla says. “Depending on the frequency of your episodes, I would probably place a one- or two-day monitor, or even up to a 30-day monitor or longer, with a consultation with our electrophysiology team. But the thought would be to make sure there are no abnormal heart rhythms underlying it.”

Abnormal heart rhythms can cause fainting. Syncope may be a symptom of heart arrhythmias such as bradycardia (a too-slow heart rate), tachycardia (a too-rapid heart rate), skipped heart beats or fluttering. “Abnormal heart rhythms don’t allow your brain to get the blood it needs, and if it doesn’t get the blood it needs, you pass out,” Grossman explains.

Fainting may be the first sign of a serious heart condition. Problems with the heart’s electrical conduction system may first become apparent when someone faints. Heart block and long QT syndrome are types of conduction disorders that have syncope as a symptom.

Syncope with activity is a danger signal. “There are things most cardiologists would say raise our red flags (including) syncope with exertion,” Favilla says. “So if people are playing sports and they fall to the ground all of a sudden, or mid-stride, as we call it.” A teen who passes out while playing sports, in some cases after reporting chest pains and heart palpitations, or fluttering, should be immediately evaluated and may require emergency care on the spot.

Cardiomyopathy can be a culprit. With syncope that raises suspicion of heart disease, cardiomyopathies must be ruled out. That means “making sure there’s not a thinned out, dilated heart; making sure there’s not a thicker heart or anything that makes us think that maybe the heart muscle doesn’t look quite right,” Favilla says. “Maybe you would then turn from going to an echo to going to a cardiac MRI.”

Seeking Treatment

Cardiac fainting causes are treatable. Once a heart-related diagnosis is made, treatments can include medication, surgery or, in rare cases, implants such as a pacemaker or implantable cardioverter defibrillator.

Getting care is essential. “The most important thing, in the moment, is to really seek care,” Favilla says. “A child who (passes out) with exertion or soon thereafter should be seen immediately. Never hesitate to contact someone if there’s syncope with sports or with any rigorous activity, or with chest pain or heart fluttering. These are really the red flags we want parents to come in for.”

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The Facts About Fainting Spells originally appeared on

Update 05/03/22: This story was previously published at an earlier date and has been updated with new information.

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