Fainting

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Fainting, also known as syncope, is a temporary loss of consciousness that most commonly occurs due to a sudden drop in blood pressure, resulting in a lack of oxygen to the brain. Most cases are non-life-threatening and resolve on their own.

But, sometimes, fainting may signify a more serious health problem. In addition, it’s possible to fall during an episode of syncope, increasing your risk of injury and medical complications.

This article will discuss fainting as a symptom, common causes, when to see a healthcare provider, tests, and treatment.

Person on floor at home after an episode of fainting

PixelsEffect / Getty Images

Symptom of Fainting

Most cases of fainting are non-life-threatening and isolated in nature, requiring little or no treatment, but if you experience any of the following associated symptoms, a more serious reason may be behind your fainting spell.

The following associated symptoms are serious and may require a more extensive workup to determine the cause of your syncope:

  • Sweating
  • Dizziness
  • Light-headedness
  • Shortness of breath
  • Nausea
  • Vomiting
  • Pale skin (particularly a lack of blood flow in the skin, the color of the skin may look different based on skin complexion)
  • A feeling of impending doom or anxiety
  • Confusion
  • Urinary or bowel incontinence

Causes of Fainting

Feeling like you’re about to pass out or lose consciousness can be scary, but many causes are benign.

The most common type of “faint" is neurocardiogenic or vasovagal syncope (also known as reflex syncope). This type of fainting typically occurs when an emotional trigger, such as the sight of blood, leads to a sudden and unpredictable drop in blood pressure. People tend to recover quickly, within a matter of minutes. The cause of vasovagal syncope is unknown.

Oftentimes, fainting is associated with non-life-threatening conditions and requires no medical treatment. Still, you should never dismiss fainting as an unimportant symptom, especially if it happens more than once over a short period of time. Causes such as heart disease require immediate medical attention.

Some of the common causes of fainting are:

  • Vasovagal or neurocardiogenic syncope (fainting due to an emotional trigger such as the sight of blood)
  • Drop in blood pressure due to standing up or sitting up too quickly (orthostatic hypotension)
  • Overheating
  • Dehydration
  • Malnutrition or not eating enough
  • Panic or extreme anxiety
  • Heart problems, such as arrhythmias (atrioventricular block and ventricular tachycardia) and heart failure (the heart does not pump enough blood for the body's needs)
  • Carotid sinus syndrome (an exaggerated response to pressure applied to the carotid sinus, an area in the neck)
  • Asthma (a chronic lung disease of constricted and inflamed airways)
  • Lung problems such as chronic obstructive pulmonary disease (COPD) or emphysema
  • Smoking
  • Certain medicines
  • Drop in blood sugar
  • Emotional stress or fear (like being in a crowded space with agoraphobia)
  • Seizure

What Medications Can Cause You to Faint

Medications are a common cause of syncope in older people who tend to have more comorbidities and engage in polypharmacy (take two or more drugs per day). Some of the most common drugs associated with syncope include:

How to Treat Fainting

Fainting is a common phenomenon that usually requires no treatment. If medication is the cause of your syncope, consult a healthcare provider to see if lowering your dose or changing the medication may prevent future episodes.

If stress is the cause, avoid situations that make you anxious. If low blood sugar is the cause, and you have diabetes, make sure you take your insulin and other diabetes medications as prescribed (for example, too much insulin can rapidly lower your blood sugar, causing you to faint).

As you age, consider making it a habit to stand up and sit down more slowly, given your higher risk of fainting and falling. 

Some people experience prodromal symptoms or feel weak and like they are about to pass out. In those cases, lie or sit down and place your head between your knees to direct blood flow to your brain.

If you observe someone fainting, assess for any visible injuries. If there are none, ensure the person is lying flat and raise their legs to direct blood flow to the brain.

If a heart problem is at the root of your syncope, your healthcare provider will create a plan to manage your condition. This may include medication therapy (like taking a statin, antihypertensive, or antiarrhythmic medication), or having surgery (like the placement of a pacemaker)

Risk Factors and Complications of Fainting

Although up to 40% of fainting spells occur in people under 25, 10%–15% of people over 65 will experience syncope, and about one-third of older adults experience recurrent episodes and injury, making advanced age the single greatest risk factor for fainting.

Any condition that lowers oxygen to the brain—mainly heart and lung disorders—can put you at risk of fainting. This includes:

  • Asthma
  • COPD
  • Emphysema
  • Bronchiectasis (an obstructive lung disease with permanent widening of the airways)
  • Congestive heart failure
  • Arrhythmias
  • Carbon monoxide poisoning
  • Cerebrovascular events such as cardiac arrest or stroke

A history of smoking, older age, obesity, diabetes, and high blood pressure are independent factors that can increase the incidence for heart disease and, therefore, indirectly increase your risk of syncope.

Are There Tests to Diagnose the Cause of Fainting

A fainting episode tends to happen quickly but may also be associated with prodromal symptoms such as sweating, dizziness, light-headedness, nausea, muscle weakness, and visual disturbances. Some questions a healthcare provider may ask include:

  • Did you lose consciousness?
  • Is this the first time you’ve experienced an episode of syncope? If not, how often has this occurred?
  • Are you on any medications?
  • Did you experience prodromal symptoms?
  • After the event, were you able to recover quickly without ongoing symptoms?

There are no set criteria to diagnose fainting, but a thorough clinical history and an electrocardiogram (ECG or EKG) have been shown to diagnose about 50% of cases.

Checking your vitals (such as blood pressure and oxygen saturation), a detailed medical history, and a focused physical are key to determining the triggers of your episode. Blood tests looking at your blood sugar and electrolyte levels may also be helpful.

If you are at high risk for a cardiovascular event, your healthcare provider may also order an ECG, echocardiogram, and a computed tomography (CT) scan of the head to rule out any damage or abnormalities in the heart and brain. If you have fallen, an X-ray may also be ordered to determine if you sustained a fracture. 

When to Call a Healthcare Provider

If you fall, get injured, or experience signs of a heart attack or stroke such as chest pain, shortness of breath, paralysis, and trouble forming words, seek immediate emergency medical attention.

If you experience fainting for any reason, check with a healthcare provider. They can rule out serious underlying conditions and may also be able to discuss pharmacological interventions and lifestyle changes that can help prevent future episodes and potential injury.

Summary

Fainting, also known as syncope, is a temporary loss of consciousness that most commonly occurs as a result of a sudden drop in blood pressure, resulting in a lack of oxygen to the brain. Common causes include emotional triggers, dehydration, standing up too quickly, and medication side effects. Causes due to heart conditions such as arrhythmias are more concerning.

See a healthcare provider if you experience a fainting episode. Tests can include a physical examination, medical history, blood tests, heart tests, and imaging. Treatment will depend on the cause.

A Word From Verywell

Fainting can be frightening to the person experiencing the event and any observers. Although the causes of fainting tend to be benign and occur mostly in people who are generally healthy, it carries the risk of falling and sustaining injuries such as bone fractures, lacerations, and traumatic brain injury.

The risk of experiencing head trauma, such as a subdural hematoma, increases as you age. Recurrent episodes may prevent you from driving and performing other daily activities. See a healthcare provider to rule out serious underlying conditions and recommend lifestyle changes that may help.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Johns Hopkins Medicine. Syncope (fainting).

  2. da Silva RM. Syncope: epidemiology, etiology, and prognosisFront Physiol. 2014;5:471. doi:10.3389/fphys.2014.00471

  3. Zagaria MAE. Syncope: medications as causes and contributing factors. US Pharm. 2012;37(3):22-27.

  4. American Heart Association. Syncope (fainting).

  5. Nemours KidsHealth. First aid: fainting.

  6. Runser LA, Gauer RL, Houser A. Syncope: evaluation and differential diagnosisAm Fam Physician. 2017;95(5):303-312B.

  7. Kenny RA. Syncope. In: Fillit HM, Rockwood K, Woodhouse K, eds. Brocklehurst’s Textbook of Geriatric Medicine and Gerontology. 7th ed. Philadelphia, PA: Saunders Elsevier; 2010:338-347.

  8. American Heart Association. Understanding your risks to prevent a heart attack.

By Shamard Charles, MD, MPH
Shamard Charles, MD, MPH is a public health physician and journalist. He has held positions with major news networks like NBC reporting on health policy, public health initiatives, diversity in medicine, and new developments in health care research and medical treatments.