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Table of Contents

Symptoms

Causes

When to See a Provider

Diagnosis and Treatment

Prevention

FAQ

Fainting (syncope) is a suddenloss of consciousnessfrom a lack of blood flow to the brain. People who have passed out usually wake up quickly after collapsing, but in some cases, fainting is a sign of a serious or potentially life-threatening condition.

This article explains the symptoms of fainting and many possible reasons why it can happen. It details diagnosis and treatment options, and offers some tips on how fainting may be prevented.

Causes of Fainting

What Fainting Feels Like

Fainting tends to affect younger people, although heart conditions and drug interactions often lead older people to pass out.  There’s a high incidence in people between the ages of 10 and 30 years, and then again in those ages 65 and older.It’s generally less common in middle-aged adults.

Most people will suddenly feel flushed and warm, become weak, and lose consciousness. When they do, they pass out and often fall (which can lead to additional injuries).Other signs and symptoms include:

Stimulation of thevagus nerveis one cause of fainting spells. The vagus is the largest nerve in the body, running from the brain to the abdomen, and it affects multiple systems (like heart rate and blood pressure) when stimulated. This can have a number of causes, including pain or stress.

Vasovagal Syncope: Why It Happens and How to Treat It

Causes of Fainting

The cause of fainting can be as simple (and temporary) as anxiety that causeshyperventilation(breathing too fast) or heat illness from working hard in the sun.But fainting can also be a symptom of a sudden and lethal heart condition.

Serious heart conditions that can cause syncope include:

If the heart beats too fast or too slow, it can’t keep the blood pressure up as high as it needs to be.Blood drains from the brain and leads to fainting. During aheart attack, the heart muscle can become too weak to maintain blood pressure.

Dehydration

Too little water in the bloodstream lowers blood pressure, and stimulating the vagus nerve when the system is already low can lead to dizziness and fainting.

There are many causes of dehydration, including vomiting or diarrhea. Vomiting and diarrhea, specifically, are related to vagus nerve function.

Shock

Shock is a life-threatening emergency that usually comes from bleeding but can also result from severe allergy (anaphylaxis).Severe infection can lead to shock. People with shock will most likely become confused, and then lose consciousness as their condition gets worse.

First Aid Instructions for 10 Medical Emergencies

Illicit Drugs or Alcohol

Alcoholmisuse andsubstance abusecan cause people to pass out. Besides its obvious sedation effect, alcohol makes people urinate, which will eventually lead to dehydration. It also dilates blood vessels, which decreases blood pressure.

Like shock, losing consciousness due to alcohol is not technically considered fainting, but it may or may not be cause for concern. It is possible to die fromalcohol poisoning, and passing out is a sign of serious intoxication.

Drug Interactions

Some medications can increase the risk of passing out, whether taken alone or when interacting with other drugs and supplements. They include:

One study of people diagnosed with type 2 diabetes found the risk of asyncopalepisode (passing out) was higher in those taking several medications (polypharmacy).Be sure to talk with a healthcare provider to limit the risk.

Orthostatic HypotensionOrthostatic hypotension(a drop in blood pressure when you stand up) can cause you to pass out suddenly. It has several potential causes, including Parkinson’s disease. But medications are one of the most common reasons for episodes of this type of fainting.It differs from postural orthostatic tachycardia syndrome (POTS), which often causes younger people to pass out when standing up.

Orthostatic Hypotension

Orthostatic hypotension(a drop in blood pressure when you stand up) can cause you to pass out suddenly. It has several potential causes, including Parkinson’s disease. But medications are one of the most common reasons for episodes of this type of fainting.It differs from postural orthostatic tachycardia syndrome (POTS), which often causes younger people to pass out when standing up.

POTS Symptoms, Causes, and Treatment

Less Common Causes of Passing Out

Some people (commonly males) can pass out when they urinate (micturitionsyncope). The exact cause is not understood but may be related to vagal response.It can occur with coughing or stretching, too.

When Kids Are Passing Out

Fainting episodes affect up to 25% of children and teens, too, and typically for the same reasons that they occur in younger adults: Heat exposure, dehydration, and hyperventilation are common. But some other causes are unique to kids, like holding their breath during temper tantrums.

Experts increasingly warn of social media influences inviting teens to play “pass out,” “blackout,” or the “fainting game.” Headaches and bloodshot eyes are common in kids playing these potentially fatal games.

If you see someone pass out, make sure the person is breathing. If not, call 911 and beginCPR.

When to See a Healthcare Provider

In some cases, sudden episodes of fainting can occur when you turn your head to the side. This can be due to pressure on the carotid artery that changes blood flow.It also can be related to health conditions likecarotid artery stenosis(blockage).

If someone faints but doesn’t wake up within a few seconds, seek medical care.

Fainting in Pregnant PeopleEpisodes of syncope are common in pregnant people, due to both hormonal changes affecting blood vessels and physical changes including the blood volume in the body.It’s usually not cause for concern but may be a symptom of a more serious problem. Your healthcare provider can diagnose the cause of passing out (or feeling like you will) while pregnant.

Fainting in Pregnant People

Episodes of syncope are common in pregnant people, due to both hormonal changes affecting blood vessels and physical changes including the blood volume in the body.It’s usually not cause for concern but may be a symptom of a more serious problem. Your healthcare provider can diagnose the cause of passing out (or feeling like you will) while pregnant.

What to Know About Low Blood Pressure and Pregnancy

Treatment for a condition that causes fainting will depend on the underlying cause. Your healthcare provider will rely on a full medical history and physical assessment. They also may order tests that include anelectrocardiogram(12-lead EKG) to check heart rhythm.

AHolter monitor test(ambulatory EKG) may be used to see how your heart rhythm changes as you perform normal daily functions for a day or two. In addition to heart function, your provider will look to see if there’s a neurological cause or ametabolic disorderthat’s responsible for fainting episodes. You may need blood work, glucose testing, or other assessments.

What Is a Tilt Table Test?A tilt table is used when the cause of fainting episodes (and related symptoms, like heart rate changes) is unknown. The table is used to change your body’s positions and watch the heart rate and other responses. It can be used to diagnosedysautonomia(problems with nerves that control functions like blood pressure), vasovagal syncope, or other reasons for passing out.

What Is a Tilt Table Test?

A tilt table is used when the cause of fainting episodes (and related symptoms, like heart rate changes) is unknown. The table is used to change your body’s positions and watch the heart rate and other responses. It can be used to diagnosedysautonomia(problems with nerves that control functions like blood pressure), vasovagal syncope, or other reasons for passing out.

Sometimes, there’s absolutely nothing you can do to stop from fainting. But if you feel an episode coming on, you can move your body in specific ways to prevent fainting. You can:

If the feeling doesn’t pass in a few minutes, or you begin to experience chest pain or shortness of breath, call 911.

To prevent passing out in the long term, you need to avoid situations that can lead to episodes, like alcohol misuse or forgetting to eat and drink. You should also try to maintain a healthy lifestyle, keep up with your healthcare appointments, and take medications as prescribed.

Summary

People who have experienced multiple fainting spells should see a healthcare provider to learn the cause. Certain tests, like a tilt table test, can help with diagnosis and treatment of syncope.

Frequently Asked QuestionsYes, it can. When you stand too long in one place with your knees locked straight, it can cause your blood to pool in your leg veins, which may cause you to faint. To prevent this from happening, make sure to bend your knees or move around a little to improve your circulation.Find ways to distract yourself. Look away when the test is being done, talk to the person doing the blood draw, or try some meditation and deep breathing exercises. Also, let the phlebotomist know if you’re prone to fainting. They may be able to let you lie down during the test.

Frequently Asked Questions

Yes, it can. When you stand too long in one place with your knees locked straight, it can cause your blood to pool in your leg veins, which may cause you to faint. To prevent this from happening, make sure to bend your knees or move around a little to improve your circulation.

Find ways to distract yourself. Look away when the test is being done, talk to the person doing the blood draw, or try some meditation and deep breathing exercises. Also, let the phlebotomist know if you’re prone to fainting. They may be able to let you lie down during the test.

16 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Johns Hopkins Medicine.Syncope (fainting).Walsh K, Hoffmayer K, Hamdan MH.Syncope: Diagnosis and management.Curr Probl Cardiol. 2015 Feb;40(2):51-86. doi:10.1016/j.cpcardiol.2014.11.001Kavi KS, Gall NP.Trauma and syncope: Looking beyond the injury.Trauma Surg Acute Care Open. 2023 Feb 2;8(1):e001036. doi:10.1136/tsaco-2022-001036Da silva RM.Syncope: Epidemiology, etiology, and prognosis.Front Physiol. 2014;5:471. doi:10.3389/fphys.2014.00471Cedars Sinai.Vasovagal syncope.Centers for Disease Control and Prevention.Preventing heat-related illness.Koene RJ, Adkisson WO, Benditt DG.Syncope and the risk of sudden cardiac death: Evaluation, management, and prevention.J Arrhythm. 2017 Dec;33(6):533-544. doi:10.1016/j.joa.2017.07.005.Hagbom M, Hellysaz A, Istrate C, Nordgren J, Sharma S, de-Faria FM,et al.The 5-HT3 receptor affects rotavirus-induced motility.J Virol. 2021 Jul 12;95(15):e0075121. doi:10.1128/JVI.00751-21Nguyen SMT, Rupprecht CP, Haque A, Pattanaik D, Yusin J, Krishnaswamy G.Mechanisms governing anaphylaxis: Inflammatory cells, mediators, endothelial gap junctions and beyond.Int J Mol Sci. 2021 Jul 21;22(15):7785. doi:10.3390/ijms22157785Rivasi G, Rafanelli M, Mossello E, Brignole M, Ungar A.Drug-related orthostatic hypotension: Beyond anti-hypertensive medications.Drugs Aging. 2020 Oct;37(10):725-738. doi:10.1007/s40266-020-00796-5Remelli F, Ceresini MG, Trevisan C, Noale M, Volpato S.Prevalence and impact of polypharmacy in older patients with type 2 diabetes.Aging Clin Exp Res. 2022 Sep;34(9):1969-1983. doi:10.1007/s40520-022-02165-1.Khan MA, Viskin S, Madias C.Micturition syncope…not always benign.Circulation. 2023;148(8):695-697.American Academy of Family Physicians.Fainting.American Academy of Pediatrics.Dizziness and fainting in children and teens.Javier RC, Singh PV, Shrestha J, Abdalla R, Narang P, Patel H,et al.Trends and immediate outcomes of syncope during pregnancy: A narrative review.Cureus. 2023 Dec 2;15(12):e49833. doi:10.7759/cureus.49833National Institute of Neurological Disorders and Stroke.Syncope.Additional ReadingProbst MA, Kanzaria HK, Gbedemah M, Richardson LD, Sun BC.National trends in resource utilization associated with ED visits for syncope.The American Journal of Emergency Medicine. 2015;33(8):998-1001. doi:10.1016/j.ajem.2015.04.030

16 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Johns Hopkins Medicine.Syncope (fainting).Walsh K, Hoffmayer K, Hamdan MH.Syncope: Diagnosis and management.Curr Probl Cardiol. 2015 Feb;40(2):51-86. doi:10.1016/j.cpcardiol.2014.11.001Kavi KS, Gall NP.Trauma and syncope: Looking beyond the injury.Trauma Surg Acute Care Open. 2023 Feb 2;8(1):e001036. doi:10.1136/tsaco-2022-001036Da silva RM.Syncope: Epidemiology, etiology, and prognosis.Front Physiol. 2014;5:471. doi:10.3389/fphys.2014.00471Cedars Sinai.Vasovagal syncope.Centers for Disease Control and Prevention.Preventing heat-related illness.Koene RJ, Adkisson WO, Benditt DG.Syncope and the risk of sudden cardiac death: Evaluation, management, and prevention.J Arrhythm. 2017 Dec;33(6):533-544. doi:10.1016/j.joa.2017.07.005.Hagbom M, Hellysaz A, Istrate C, Nordgren J, Sharma S, de-Faria FM,et al.The 5-HT3 receptor affects rotavirus-induced motility.J Virol. 2021 Jul 12;95(15):e0075121. doi:10.1128/JVI.00751-21Nguyen SMT, Rupprecht CP, Haque A, Pattanaik D, Yusin J, Krishnaswamy G.Mechanisms governing anaphylaxis: Inflammatory cells, mediators, endothelial gap junctions and beyond.Int J Mol Sci. 2021 Jul 21;22(15):7785. doi:10.3390/ijms22157785Rivasi G, Rafanelli M, Mossello E, Brignole M, Ungar A.Drug-related orthostatic hypotension: Beyond anti-hypertensive medications.Drugs Aging. 2020 Oct;37(10):725-738. doi:10.1007/s40266-020-00796-5Remelli F, Ceresini MG, Trevisan C, Noale M, Volpato S.Prevalence and impact of polypharmacy in older patients with type 2 diabetes.Aging Clin Exp Res. 2022 Sep;34(9):1969-1983. doi:10.1007/s40520-022-02165-1.Khan MA, Viskin S, Madias C.Micturition syncope…not always benign.Circulation. 2023;148(8):695-697.American Academy of Family Physicians.Fainting.American Academy of Pediatrics.Dizziness and fainting in children and teens.Javier RC, Singh PV, Shrestha J, Abdalla R, Narang P, Patel H,et al.Trends and immediate outcomes of syncope during pregnancy: A narrative review.Cureus. 2023 Dec 2;15(12):e49833. doi:10.7759/cureus.49833National Institute of Neurological Disorders and Stroke.Syncope.Additional ReadingProbst MA, Kanzaria HK, Gbedemah M, Richardson LD, Sun BC.National trends in resource utilization associated with ED visits for syncope.The American Journal of Emergency Medicine. 2015;33(8):998-1001. doi:10.1016/j.ajem.2015.04.030

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Johns Hopkins Medicine.Syncope (fainting).Walsh K, Hoffmayer K, Hamdan MH.Syncope: Diagnosis and management.Curr Probl Cardiol. 2015 Feb;40(2):51-86. doi:10.1016/j.cpcardiol.2014.11.001Kavi KS, Gall NP.Trauma and syncope: Looking beyond the injury.Trauma Surg Acute Care Open. 2023 Feb 2;8(1):e001036. doi:10.1136/tsaco-2022-001036Da silva RM.Syncope: Epidemiology, etiology, and prognosis.Front Physiol. 2014;5:471. doi:10.3389/fphys.2014.00471Cedars Sinai.Vasovagal syncope.Centers for Disease Control and Prevention.Preventing heat-related illness.Koene RJ, Adkisson WO, Benditt DG.Syncope and the risk of sudden cardiac death: Evaluation, management, and prevention.J Arrhythm. 2017 Dec;33(6):533-544. doi:10.1016/j.joa.2017.07.005.Hagbom M, Hellysaz A, Istrate C, Nordgren J, Sharma S, de-Faria FM,et al.The 5-HT3 receptor affects rotavirus-induced motility.J Virol. 2021 Jul 12;95(15):e0075121. doi:10.1128/JVI.00751-21Nguyen SMT, Rupprecht CP, Haque A, Pattanaik D, Yusin J, Krishnaswamy G.Mechanisms governing anaphylaxis: Inflammatory cells, mediators, endothelial gap junctions and beyond.Int J Mol Sci. 2021 Jul 21;22(15):7785. doi:10.3390/ijms22157785Rivasi G, Rafanelli M, Mossello E, Brignole M, Ungar A.Drug-related orthostatic hypotension: Beyond anti-hypertensive medications.Drugs Aging. 2020 Oct;37(10):725-738. doi:10.1007/s40266-020-00796-5Remelli F, Ceresini MG, Trevisan C, Noale M, Volpato S.Prevalence and impact of polypharmacy in older patients with type 2 diabetes.Aging Clin Exp Res. 2022 Sep;34(9):1969-1983. doi:10.1007/s40520-022-02165-1.Khan MA, Viskin S, Madias C.Micturition syncope…not always benign.Circulation. 2023;148(8):695-697.American Academy of Family Physicians.Fainting.American Academy of Pediatrics.Dizziness and fainting in children and teens.Javier RC, Singh PV, Shrestha J, Abdalla R, Narang P, Patel H,et al.Trends and immediate outcomes of syncope during pregnancy: A narrative review.Cureus. 2023 Dec 2;15(12):e49833. doi:10.7759/cureus.49833National Institute of Neurological Disorders and Stroke.Syncope.

Johns Hopkins Medicine.Syncope (fainting).

Walsh K, Hoffmayer K, Hamdan MH.Syncope: Diagnosis and management.Curr Probl Cardiol. 2015 Feb;40(2):51-86. doi:10.1016/j.cpcardiol.2014.11.001

Kavi KS, Gall NP.Trauma and syncope: Looking beyond the injury.Trauma Surg Acute Care Open. 2023 Feb 2;8(1):e001036. doi:10.1136/tsaco-2022-001036

Da silva RM.Syncope: Epidemiology, etiology, and prognosis.Front Physiol. 2014;5:471. doi:10.3389/fphys.2014.00471

Cedars Sinai.Vasovagal syncope.

Centers for Disease Control and Prevention.Preventing heat-related illness.

Koene RJ, Adkisson WO, Benditt DG.Syncope and the risk of sudden cardiac death: Evaluation, management, and prevention.J Arrhythm. 2017 Dec;33(6):533-544. doi:10.1016/j.joa.2017.07.005.

Hagbom M, Hellysaz A, Istrate C, Nordgren J, Sharma S, de-Faria FM,et al.The 5-HT3 receptor affects rotavirus-induced motility.J Virol. 2021 Jul 12;95(15):e0075121. doi:10.1128/JVI.00751-21

Nguyen SMT, Rupprecht CP, Haque A, Pattanaik D, Yusin J, Krishnaswamy G.Mechanisms governing anaphylaxis: Inflammatory cells, mediators, endothelial gap junctions and beyond.Int J Mol Sci. 2021 Jul 21;22(15):7785. doi:10.3390/ijms22157785

Rivasi G, Rafanelli M, Mossello E, Brignole M, Ungar A.Drug-related orthostatic hypotension: Beyond anti-hypertensive medications.Drugs Aging. 2020 Oct;37(10):725-738. doi:10.1007/s40266-020-00796-5

Remelli F, Ceresini MG, Trevisan C, Noale M, Volpato S.Prevalence and impact of polypharmacy in older patients with type 2 diabetes.Aging Clin Exp Res. 2022 Sep;34(9):1969-1983. doi:10.1007/s40520-022-02165-1.

Khan MA, Viskin S, Madias C.Micturition syncope…not always benign.Circulation. 2023;148(8):695-697.

American Academy of Family Physicians.Fainting.

American Academy of Pediatrics.Dizziness and fainting in children and teens.

Javier RC, Singh PV, Shrestha J, Abdalla R, Narang P, Patel H,et al.Trends and immediate outcomes of syncope during pregnancy: A narrative review.Cureus. 2023 Dec 2;15(12):e49833. doi:10.7759/cureus.49833

National Institute of Neurological Disorders and Stroke.Syncope.

Probst MA, Kanzaria HK, Gbedemah M, Richardson LD, Sun BC.National trends in resource utilization associated with ED visits for syncope.The American Journal of Emergency Medicine. 2015;33(8):998-1001. doi:10.1016/j.ajem.2015.04.030

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