Fainting (Syncope)

Fainting (Syncope) Symptoms & Signs

Medical Author:

Related
Symptoms & Signs

Fainting (syncope) is the partial or complete loss of consciousness with interruption of awareness of oneself and ones surroundings. When the loss of consciousness is temporary and there is spontaneous recovery, it is referred to as syncope or, in nonmedical terms, fainting. Syncope accounts for one in every 30 visits to an emergency room. It is pronounced sin-ko-pea.

Syncope is due to a temporary reduction in blood flow and therefore a shortage of oxygen to the brain. This leads to lightheadedness or a "black out" episode, a loss of consciousness. Temporary impairment of the blood supply to the brain can be caused by heart conditions and by conditions that do not directly involve the heart.

Medically Reviewed by a Doctor on 5/1/2017

Health concern on your mind? Visit the Symptom Checker.

REFERENCE:

Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.

Main Article on Fainting
  • Fainting Fainting, also referred to as blacking out, syncope, or temporary loss of consciousness has many causes. Often a person will have...learn more »
Pictures, Images, Illustrations & Quizzes
Causes of Fainting
    • Anaphylaxis Anaphylaxis is a serious allergic reaction that affects a number of different areas of the body at one time, and can be fatal....learn more »
      In This Article
      Anaphylaxis Article
      • Anaphylaxis facts
      • What is anaphylaxis?
      • What is the history of anaphylaxis?
      • What are common causes of anaphylaxis?
      • What are anaphylaxis symptoms and signs?
      • Are there any disorders that appear similar to anaphylaxis?
      • How is anaphylaxis diagnosed?
      • Recommendations after an initial episode of anaphylaxis
      • What are emergency measures used in the treatment of anaphylaxis?
      • What is the treatment for anaphylaxis?
      • Is it possible to prevent anaphylaxis?
      • What is the prognosis of anaphylaxis?
    • Anemia Anemia is the condition of having less than the normal number of red blood cells or less than the normal quantity of hemoglobin...learn more »
    • Aortic Dissection Aortic dissection is a small tear in the large blood vessel that leads from the heart and supplies blood to the body. There are...learn more »
      In This Article
      Aortic Dissection Article
      • Aortic dissection facts
      • Introduction to aortic dissection
      • What are the causes of aortic dissection?
      • What are the signs and symptoms of aortic dissection?
      • How is aortic dissection diagnosed?
      • What is the treatment for aortic dissection?
      • What is the prognosis for aortic dissection?
      • Can aortic dissection be prevented?
    • Aortic Stenosis Aortic valve stenosis is an abnormal narrowing of the aortic valve of the heart. The causes of aortic stenosis are wear and tear...learn more »
      In This Article
      Aortic Stenosis Article
      • Aortic valve stenosis facts
      • What is aortic stenosis?
      • What causes aortic stenosis?
      • How does aortic stenosis affect the left ventricle pump?
      • What are the symptoms of aortic stenosis?
      • What might the doctor find in patients with aortic stenosis?
      • How is aortic stenosis diagnosed?
      • How is aortic stenosis treated?
    • Atrial Fibrillation Symptoms (AFib Warning Signs) Atrial fibrillation or AFib is a type of hear rhythm abnormality. Early warning signs and symptoms of atrial fibrillation...learn more »
      In This Article
      Atrial Fibrillation Symptoms (AFib Warning Signs) Article
      • What is atrial fibrillation?
      • What are the signs and symptoms of atrial fibrillation?
      • What does atrial fibrillation feel like?
      • Who is at risk for atrial fibrillation?
      • Are heart attack or stroke symptoms different from atrial fibrillation symptoms?
      • Do all types of atrial fibrillation have the same symptoms?
      • What is the treatment and management of atrial fibrillation symptoms?
      • What is the prognosis and life expectancy for a person with atrial fibrillation?
    • Atrial Flutter vs. Atrial Fibrillation (What Are the Differences?) Atrial flutter and atrial fibrillation (AFib) are two types of a heart problem called atrial tachycardia. Both of these...learn more »
      In This Article
      Atrial Flutter vs. Atrial Fibrillation (What Are the Differences?) Article
      • What is atrial flutter, and what is atrial fibrillation (definitions)?
      • Are atrial flutter, atrial tachycardia, and atrial fibrillation the same thing?
      • What are the differences in how atrial flutter and AFib affect the heart (ECG wave strip patterns)?
      • Which heart condition is more serious, atrial flutter or atrial fibrillation?
      • What's the difference between how these two heart conditions feel (symptoms); can you feel atrial flutter and/or atrial fibrillation?
      • Do the causes and risk factors for atrial flutter and atrial fibrillation differ?
      • What is the difference between the treatments for atrial flutter and atrial fibrillation?
      • Can either of these conditions be prevented?
      • What is the prognosis for someone with atrial fibrillation or atrial flutter?
    • Cardiomyopathy (Dilated) Dilated Cardiomyopathy is a condition where the heart's ability to pump blood is decreased because the heart's main pumping...learn more »
      In This Article
      Cardiomyopathy (Dilated) Article
      • What Is dilated cardiomyopathy?
      • What are the symptoms of Dilated Cardiomyopathy?
      • What causes Dilated Cardiomyopathy?
      • How is Dilated Cardiomyopathy diagnosed?
      • What is the treatment for Dilated Cardiomyopathy?
      • What surgeries are used to treat Dilated Cardiomyopathy?
    • Cardiomyopathy (Hypertrophic) Hypertrophic cardiomyopathy (HCM) affects many people today. Many people with HCM have no symptoms or only minor symptoms, and...learn more »
      In This Article
      Cardiomyopathy (Hypertrophic) Article
      • What is hypertrophic cardiomyopathy?
      • What are the symptoms of hypertrophic cardiomyopathy?
      • What causes hypertrophic cardiomyopathy?
      • How is hypertrophic cardiomyopathy diagnosed?
      • How is hypertrophic cardiomyopathy treated?
      • What lifestyle changes are recommended to treat hypertrophic cardiomyopathy?
      • What medications are used for hypertrophic cardiomyopathy?
      • What surgical procedures are used to treat hypertrophic cardiomyopathy?
      • How can I prevent endocarditis?
    • Cardiomyopathy (Restrictive) Restrictive cardiomyopathy, the rarest form of cardiomyopathy, is a condition in which the walls of the lower chambers of the...learn more »
      In This Article
      Cardiomyopathy (Restrictive) Article
      • What is restrictive cardiomyopathy?
      • What are the symptoms of restrictive cardiomyopathy?
      • What causes restrictive cardiomyopathy?
      • How is restrictive cardiomyopathy diagnosed?
      • What is the treatment for restrictive cardiomyopathy?
      • What lifestyle changes are recommended for restrictive cardiomyopathy?
      • What medications are used for restrictive cardiomyopathy?
      • Can surgery treat restrictive cardiomyopathy?
    • Chagas Disease (American Trypanosomiasis or Kissing Bug Disease) Chagas disease is an infection caused by the T. cruzi parasite. Symptoms of Chagas disease include rash, swollen lymph nodes,...learn more »
      In This Article
      Chagas Disease (American Trypanosomiasis or Kissing Bug Disease) Article
      • Chagas disease (kissing bug disease) facts
      • What is Chagas disease?
      • What is the history of Chagas disease?
      • What causes Chagas disease?
      • Is Chagas disease contagious?
      • What are the risk factors for Chagas disease?
      • What are symptoms and signs of Chagas disease?
      • How do health-care professionals diagnose Chagas disease?
      • What is the treatment for Chagas disease?
      • What types of physicians treat Chagas disease?
      • Can transmission of Chagas disease be prevented with a vaccine?
      • What is the prognosis for Chagas disease?
      • What are the complications of Chagas disease?
      • What research is being done for Chagas disease?
    • Chest Pain Chest pain is a common complaint by a patient in the ER. Causes of chest pain include broken or bruised ribs, pleurisy,...learn more »
      In This Article
      Chest Pain Article
      • Chest pain facts
      • Chest pain introduction
      • What are the sources of chest pain?
      • What are the causes of chest pain?
      • How is chest pain diagnosed?
      • What is the philosophy of the approach to chest pain diagnosis?
      • What is the diagnosis and treatment for chest pain?
      • Broken or bruised ribs
      • Costochondritis
      • Pleuritis or pleurisy
      • Pneumothorax
      • Shingles
      • Pneumonia
      • Pulmonary embolism
      • Angina and heart attack (myocardial infarction)
      • Pericarditis
      • Aorta and aortic dissection
      • Esophagus and reflux esophagitis
      • Referred abdominal pain
    • Dehydration Dehydration is the excessive loss of body water. There are a number of causes of dehydration including heat exposure, prolonged...learn more »
      In This Article
      Dehydration Article
      • Dehydration facts
      • What is dehydration?
      • What causes dehydration?
      • Dehydration pictures
      • What are the signs and symptoms of dehydration?
      • What about dehydration in children?
      • How is dehydration diagnosed?
      • How is dehydration treated?
      • Can I treat dehydration at home?
      • What are the complications of dehydration?
      • Can dehydration be prevented?
    • Diabetes (Type 1 and Type 2) Diabetes is a chronic condition characterized by high levels of sugar (glucose) in the blood. The two types of diabetes are...learn more »
      In This Article
      Diabetes (Type 1 and Type 2) Article
      • Diabetes type 1 and type 2 definition and facts
      • What is diabetes?
      • How many people in the US have diabetes?
      • 9 early signs and symptoms of diabetes
      • How do I know if I have diabetes?
      • What causes diabetes?
      • What are the risk factors for diabetes?
      • What are the different types of diabetes?
      • What is type 1 diabetes
      • What is type 2 diabetes
      • What are the other types of diabetes?
      • What kind of doctor treats diabetes?
      • How is diabetes diagnosed?
      • Why is blood sugar checked at home?
      • What are the acute complications of diabetes?
      • What are the chronic complications of diabetes?
      • What can be done to slow the complications of diabetes?
      • What is the prognosis for a person with diabetes?
    • Early Pregnancy Symptoms and Signs Pregnancy symptoms can vary from woman to woman, and not all women experience the same symptoms. When women do experience...learn more »
      In This Article
      Early Pregnancy Symptoms and Signs Article
      • Early pregnancy symptoms and signs facts
      • How soon do early pregnancy symptoms start?
      • Are pregnancy symptoms the same for every woman?
      • 16 signs and symptoms of early pregnancy
      • What are the later signs and symptoms and signs of pregnancy?
      • What options help soothe and relieve pregnancy symptoms?
      • Pregnancy symptoms vs. PMS (premenstrual syndrome)
    • Heart Attack Treatment A heart attack involves damage or death of part of the heart muscle due to a blood clot. The aim of heart attack treatment is to...learn more »
      In This Article
      Heart Attack Treatment Article
      • What is a heart attack?
      • How is a heart attack treated?
      • Antiplatelet agents
      • Aspirin
      • Thienopyridines
      • Glycoprotein IIb/IIIa inhibitors
      • Anticoagulants
      • Clot-dissolving drugs
      • Coronary angiography and percutaneous transluminal coronary angioplasty (PTCA)
      • Coronary artery stents
      • Nitrates
      • Angiotensin converting enzyme (ACE) inhibitors
      • Beta blockers
      • Oxygen
      • Coronary artery bypass
      • What can a patient expect during recovery from a heart attack?
      • How can a second heart attack be prevented?
    • Heart Disease Heart disease (coronary artery disease) occurs when plaque builds up in the coronary arteries, the vessels that supply blood to...learn more »
      In This Article
      Heart Disease Article
      • Heart (cardiovascular) disease definition and facts
      • What is heart (cardiovascular) disease?
      • Who is at risk for heart (cardiovascular) disease?
      • What are the signs and symptoms of heart (cardiovascular) disease?
      • What causes heart (cardiovascular) disease?
      • How is heart (cardiovascular) disease diagnosed?
      • What is the treatment for heart (cardiovascular) disease?
      • What lifestyle changes can a person make to prevent further heart disease or heart attack?
      • What is the medical treatment for heart (cardiovascular) disease?
      • How many people have heart (cardiovascular) disease, and what is the prognosis?
      • Can cardiovascular disease be prevented?
    • Insect Sting Allergies The majority of stinging insects in the United States are from bees, yellow jackets, hornets, wasps, and fire ants. Severity of...learn more »
      In This Article
      Insect Sting Allergies Article
      • Stinging insect allergy facts
      • What are stinging insects?
      • What types of insect sting reactions occur?
      • What are signs and symptoms of insect sting allergies?
      • Who is at risk for insect sting allergies?
      • What tests do doctors use to diagnose an insect sting allergy?
      • What specialists treat insect sting allergies?
      • What is the treatment for a severe allergic reaction?
      • Are there home remedies for insect sting allergies?
      • How can I avoid insect stings?
      • What can I do about becoming immune to insect allergy?
      • What is the prognosis for an insect sting allergy?
    • Low Blood Pressure (Hypotension) Low blood pressure, also referred to as hypotension, is blood pressure that is so low that it causes symptoms or signs due to the...learn more »
    • Migraine Headache Migraine headaches are severe headaches that are sensitive to light, sounds, and smells. Some people who suffer from...learn more »
      In This Article
      Migraine Headache Article
      • Migraine headache definition and facts
      • What is a migraine headache?
      • What is migraine with aura?
      • What are migraine triggers?
      • What are the signs and symptoms?
      • What causes migraines?
      • What are the risk factors?
      • How can I tell if it's a migraine or a different type of headache?
      • What are the treatments for migraine headaches?
      • Migraine medications
      • What remedies and lifestyle changes help manage and decrease the frequency of migraines?
      • How are migraines managed during pregnancy?
      • How are migraines managed in children?
      • What is the prognosis for a person with migraines?
      • Can the frequency of headaches be prevented?
    • Parkinson's Disease Parkinson's disease is a slowly progressive neurological disease characterized by a fixed inexpressive face, a tremor at rest,...learn more »
      In This Article
      Parkinson's Disease Article
      • Parkinson's disease facts
      • What is Parkinson's disease?
      • What causes Parkinson's disease?
      • What genes are linked to Parkinson's disease?
      • Who is at risk for Parkinson's disease?
      • What are the symptoms of Parkinson's disease?
      • What other conditions resemble Parkinson's disease?
      • How is Parkinson's disease diagnosed?
      • What is the treatment for Parkinson's disease?
      • How can people learn to cope with Parkinson's disease?
      • Can Parkinson's disease be prevented?
      • What is the prognosis of Parkinson's disease?
    • POTS (POT Syndrome, Postural Orthostatic Tachycardia Syndrome) POT syndrome (POTS, postrual orthostatic tachycardia syndrome) is a nervous system disorder that causes lightheadedness and...learn more »
      In This Article
      POTS (POT Syndrome, Postural Orthostatic Tachycardia Syndrome) Article
      • POT syndrome definition and facts*
      • What is postural tachycardia syndrome?
      • Who gets POT syndrome?
      • What causes POT syndrome?
      • What are the signs and symptoms of POT syndrome?
      • Is there any treatment?
      • What is the prognosis?
      • What research is being done?
    • Pulmonary Hypertension (Symptoms, Treatment Medications, Life Expectancy) Pulmonary hypertension is an increase pressure in the pulmonary arteries that carry blood from the lungs to the heart. The most...learn more »
      In This Article
      Pulmonary Hypertension (Symptoms, Treatment Medications, Life Expectancy) Article
      • Pulmonary hypertension definition and facts
      • What is pulmonary hypertension?
      • Signs and symptoms of pulmonary hypertension
      • Which diseases are common in people with the condition?
      • Classification of primary and secondary pulmonary hypertension
      • What causes pulmonary hypertension?
      • How is pulmonary hypertension diagnosed?
      • What is the treatment for pulmonary hypertension?
      • Medications
      • Is there a cure?
      • What is the life expectancy?
      • Which types of doctors treat pulmonary hypertension?
    • Shock (Medical) Medical shock is a life-threatening medical condition. There are several types of medical shock, including: septic shock,...learn more »
      In This Article
      Shock (Medical) Article
      • Shock facts
      • What is shock?
      • What are the types of shock?
      • What are the causes of shock?
      • What are the symptoms of shock?
      • When should I seek medical care for shock?
      • What is the treatment for shock?
      • Can shock be prevented?
      • What is the outlook for shock?
    • Stroke (Signs, Symptoms, Warning Signs) A stroke is an interruption of the blood supply to part of the brain caused by either a blood clot (ischemic) or bleeding...learn more »
      In This Article
      Stroke (Signs, Symptoms, Warning Signs) Article
      • Stroke definition and facts
      • What is a stroke?
      • What is the NIH Stroke Scale?
      • What are the risk factors for stroke?
      • What are the warning signs and symptoms of a stroke?
      • What are the signs and symptoms of a stroke?
      • What is a transient ischemic attack (TIA)?
      • What are the types of stroke?
      • What causes a stroke?
      • What tests diagnose stroke?
      • What is the treatment for stroke?
      • Is recovery after a stroke possible?
      • What is stroke rehabilitation?
      • What is the prognosis for a person that suffers a stroke?
      • Which specialties of doctors treat stroke?
      • Can strokes be prevented?
Other Causes of Fainting

Non-heart Causes: Syncope is most commonly caused by conditions that do not directly involve the heart. These conditions include the following:

  • Postural (orthostatic) hypotension: drop in blood pressure due to changing body position to a more vertical position after lying or sitting
  • Diseases of the nerves to the legs in older people (especially with diabetes or Parkinson's disease) when poor tone of the nerves of the legs draws blood into the legs from the brain
  • High altitude
  • Fainting after certain situations (situational syncope) such as
    • blood drawing,
    • urinating (micturition syncope),
    • defecating (defecation syncope),
    • swallowing (swallowing syncope),
    • coughing (cough syncope) that trigger a reflex of the involuntary nervous system (the vasovagal reaction) that slows the heart and dilates blood vessels in the legs and cause one to feel nausea, sweating, or weakness just before fainting.

Heart Causes: Heart conditions that can cause syncope or fainting due to temporary loss of consciousness include:

Medications can cause fainting by altering blood pressure or by affecting the heart.



Symptoms & Signs A-Z List