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Blacking out
Fainted / passed out right after having food
Dizziness
Blackout for a second
Dizzy
Faint
Vertigo
Not seeing your symptoms? No worries!
What is Vasovagal Reflex?
Vasovagal reflex is a sudden drop in heart rate and blood pressure that leads to fainting. It can be triggered by stress, long periods of standing, heat exposure, or the sight of blood or anything unpleasant.
Typical Symptoms of Vasovagal Reflex
- Fainting
- Dizziness
- Feel unsteady or floating when I am standing
- Cold sweat
- Losing consciousness after moving my neck
- Feeling lightheaded or fainting after passing urine or stool
- Losing consciousness during or after meals
- Dizziness when standing or after prolonged standing
Diagnostic Questions for Vasovagal Reflex
Your doctor may ask these questions to check for this disease:
- Have you fainted recently?
- Do you feel dizzy?
- Do you feel dizzy or floaty when standing?
- Have you been experiencing cold sweats lately?
- Did you faint when you turned or moved your neck?
Treatment of Vasovagal Reflex
A doctor will usually first try to rule out more serious causes of fainting. Vasovagal reflex/syncope typically requires no further treatment. Avoiding triggers and staying hydrated can help. In rare cases, a pacemaker may be required.
Reviewed By:
Scott Nass, MD, MPA, FAAFP, AAHIVS (Primary Care)
Dr. Nass received dual medical degrees from the David Geffen School of Medicine at UCLA and Charles R. Drew University in Medicine and Science. He completed Family Medicine residency at Ventura County Medical Center with subsequent fellowships at Ventura, University of North Carolina-Chapel Hill, George Washington University, and University of California-Irvine. He holds faculty appointments at Keck School of Medicine of USC, Loma Linda University School of Medicine, and Western University of Health Sciences.
Tatsuya Shiraishi, MD (Cardiology)
Dr. Shiraishi graduated from the Kyoto University School of Medicine. He worked as a cardiologist at Edogawa Hospital, and after joining Ubie, he became the Director of East Nihonbashi Internal Medicine Clinic.
Content updated on Feb 19, 2025
Following the Medical Content Editorial Policy
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- Feel anxiety suddenly
- Felt nauseous then fainted
- Sudden sweating
- Dizziness multiple times
- Sweating followed by fainting
- Fainting followed by a headache
- Off-balance like floating
- Fainting when walking
- Chest pain with fainting
- Cold sweats
- Spinning feeling
- Feeling faint before losing consciousness
- Confused or drowsy for a while after recovering consciousness
- A sense of motion or spinning (vertigo)
- Fainting when tired
See full list
Symptoms Related to Vasovagal Reflex
Diseases Related to Vasovagal Reflex
FAQs
Q.
How to Stop a Vagal Response Fast
A.
To stop a vagal response fast, act at the first warning signs. Lie flat with legs elevated, use counterpressure maneuvers, try a brief Valsalva, breathe slowly, and sip cold water or cool down; there are several factors to consider, and the complete step by step guidance is below. For prevention and safety, see below for hydration and salt strategies, compression garments, tilt training, optional medications, and clear signs that mean you should seek medical care, such as recurrent episodes, injury, chest pain, irregular heartbeat, or neurological symptoms.
References:
Brignole M, et al. (2018). 2018 ESC guidelines for the diagnosis and management of… Eur Heart J, 29193812.
https://pubmed.ncbi.nlm.nih.gov/29193812/
Kamath PS, & Wiesner RH. (2001). A model to predict survival in patients with end-stage… Hepatology, 11157951.
https://pubmed.ncbi.nlm.nih.gov/11157951/
European Association for the Study of the Liver. (2018). EASL clinical practice guidelines for the management of patients with decompensated… Journal of Hepatology, 29467035.
Q.
Vagal Response Symptoms That Don’t Mean Something Serious
A.
Most vagal responses are brief and harmless, often triggered by stress, prolonged standing, heat, or straining, and cause lightheadedness, blurred or tunnel vision, nausea, clammy sweating, pallor, yawning, warmth, weakness, or ringing in the ears that resolve quickly with resting and fluids. There are several factors to consider, including which red flag symptoms mean you should seek urgent care and which simple first aid and prevention steps can help, so see the complete guidance below to understand more and choose the right next steps.
References:
Brignole M, & Moya A. (2018). 2018 ESC Guidelines for the diagnosis and management of… European Heart Journal, 29718436.
https://pubmed.ncbi.nlm.nih.gov/29718436/
European Association for the Study of the Liver & Latin American Association for the Study of the Liver. (2015). EASL–ALEH Clinical Practice Guidelines: Non-invasive tests for evaluation of… Journal of Hepatology, 26073518.
https://pubmed.ncbi.nlm.nih.gov/26073518/
European Association for the Study of the Liver. (2018). EASL clinical practice guidelines for the management of patients with decompensated… Journal of Hepatology, 29887330.
Q.
Age 65+: what is a vagal response, and why does it happen?
A.
A vagal response is an overactivation of the vagus nerve that abruptly slows the heart and widens blood vessels, dropping blood pressure and sometimes causing dizziness or fainting. In adults 65 and older it happens more easily due to age-related changes in blood pressure control, dehydration or lower blood volume, and medications, and it can be triggered by pain, emotional stress, heat, straining, or standing up quickly. There are several factors to consider; see below for complete details on warning signs, prevention, testing, and when to seek care that could guide your next steps.
References:
Shen WK, Sheldon RS, Benditt DG, Cohen MI, Forman DE, Goldberger ZD, et al. (2008). Neurally mediated syncope: mechanisms and therapy. The American Journal of Medicine, 18225831.
https://pubmed.ncbi.nlm.nih.gov/18225831/
Kamath PS, & Wiesner RH. (2001). A model to predict survival in patients with end-stage liver disease. Hepatology, 11157951.
https://pubmed.ncbi.nlm.nih.gov/11157951/
European Association for the Study of the Liver. (2018). EASL clinical practice guidelines for the management of patients with decompensated cirrhosis. Journal of Hepatology, 30099274.
Q.
Can dehydration or constipation trigger defecation syncope?
A.
Dehydration and constipation can contribute to defecation syncope because they may lower blood pressure or strain the body, leading to fainting during bowel movements. See below to understand more.
References:
Kapoor WN, Peterson J, & Karpf M. (1986). Defecation syncope. A symptom with multiple etiologies. Archives of internal medicine, 3778072.
https://pubmed.ncbi.nlm.nih.gov/3778072/
Brignole M. (2005). Neurally-mediated syncope. Italian heart journal : official journal of the Italian Federation of Cardiology, 15875516.
https://pubmed.ncbi.nlm.nih.gov/15875516/
Hilz MJ, Marthol H, & Neundörfer B. (2002). [Syncope - a systematic overview of classification, .... Fortschritte der Neurologie-Psychiatrie, 11823926.
Q.
How can I tell if my lightheadedness while pooping is defecation syncope or something else?
A.
Lightheadedness while pooping might be defecation syncope, which happens when you faint due to changes in blood flow. Other causes could be related to different health issues, so it's important to talk to a doctor if you're worried. See below to understand more.
References:
Kapoor WN, Peterson J, & Karpf M. (1986). Defecation syncope. A symptom with multiple etiologies. Archives of internal medicine, 3778072.
https://pubmed.ncbi.nlm.nih.gov/3778072/
Komatsu K, Sumiyoshi M, Abe H, Kohno R, Hayashi H, Sekita G, et al. (2010). Clinical Characteristics of Defecation Syncope Compared .... Circulation journal : official journal of the Japanese Circulation Society, 20032564.
https://pubmed.ncbi.nlm.nih.gov/20032564/
Hilz MJ, Marthol H, & Neundörfer B. (2002). [Syncope - a systematic overview of classification, .... Fortschritte der Neurologie-Psychiatrie, 11823926.
Q.
Should people with defecation syncope see a cardiologist or a neurologist?
A.
People with defecation syncope should consider seeing a neurologist, as this condition may involve issues related to the nervous system. See below to understand more.
References:
Rudziński A, Oko-Lagan J, & Kuźma J. (2007). [Syncope in children and adolescents]. Przeglad lekarski, 18431921.
https://pubmed.ncbi.nlm.nih.gov/18431921/
Adam MP, Feldman J, Mirzaa GM, Pagon RA, Wallace SE, Amemiya A, et al. (1993). SCN9A Neuropathic Pain Syndromes. Unknown Journal, 20301342.
Q.
Is defecation syncope dangerous or just embarrassing?
A.
Defecation syncope can be more than just embarrassing; it might be dangerous, especially if linked to other health issues. See below to understand more.
References:
Komatsu K, Sumiyoshi M, Abe H, Kohno R, Hayashi H, Sekita G, et al. (2010). Clinical Characteristics of Defecation Syncope Compared .... Circulation journal : official journal of the Japanese Circulation Society, 20032564.
https://pubmed.ncbi.nlm.nih.gov/20032564/
Kollef MH, & Schachter DT. (1991). Acute pulmonary embolism triggered by the act of defecation. Chest, 1989798.
https://pubmed.ncbi.nlm.nih.gov/1989798/
Whitley NT, & Stepien RL. (2001). Defaecation syncope and pulmonary thromboembolism in .... Australian veterinary journal, 11491217.
Q.
Can abdominal pain be caused by a vagus nerve condition?
A.
Yes, abdominal pain can be influenced by conditions related to the vagus nerve. The vagus nerve plays a significant role in regulating various bodily functions, including digestion, and disturbances in its function can lead to gastrointestinal symptoms, including abdominal pain.
References:
Gottfried-Blackmore A, Habtezion A, Nguyen L. Noninvasive vagal nerve stimulation for gastroenterology pain disorders. Pain Manag. 2021 Jan;11(1):89-96. doi: 10.2217/pmt-2020-0067. Epub 2020 Oct 28. PMID: 33111642; PMCID: PMC7787175.
Zurowski D, Nowak Ł, Wordliczek J, Dobrogowski J, Thor PJ. Effects of vagus nerve stimulation in visceral pain model. Folia Med Cracov. 2012;52(1-2):57-69. PMID: 23697215.
Hjelland IE, Hausken T, Svebak S, Olafsson S, Berstad A. Vagal tone and meal-induced abdominal symptoms in healthy subjects. Digestion. 2002;65(3):172-6. doi: 10.1159/000064937. PMID: 12138322.
Q.
What causes a vagal response while on the toilet?
A.
A vagal reaction while on the toilet, often leading to defecation syncope (fainting), is typically caused by straining during bowel movements, which triggers the vagus nerve. This can lead to a sudden drop in blood pressure and heart rate.
References:
Bae MH, Kang JK, Kim NY, Choi WS, Kim KH, Park SH, Lee JH, Yang DH, Park HS, Cho Y, Chae SC, Jun JE. Clinical characteristics of defecation and micturition syncope compared with common vasovagal syncope. Pacing Clin Electrophysiol. 2012 Mar;35(3):341-7. doi: 10.1111/j.1540-8159.2011.03290.x. Epub 2011 Dec 21. PMID: 22188510.
Tigga MP. An Unusual Case of Defecation Syncope. J Midlife Health. 2019 Apr-Jun;10(2):99-100. doi: 10.4103/jmh.JMH_2_19. PMID: 31391761; PMCID: PMC6643707.
Aydin MA, Salukhe TV, Wilke I, Willems S. Management and therapy of vasovagal syncope: A review. World J Cardiol. 2010 Oct 26;2(10):308-15. doi: 10.4330/wjc.v2.i10.308. PMID: 21160608; PMCID: PMC2998831.
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Jardine DL, Wieling W, Brignole M, Lenders JWM, Sutton R, Stewart J (Year). The pathophysiology of the vasovagal response. Heart rhythm.
https://pubmed.ncbi.nlm.nih.gov/29246828/Alboni P, Alboni M (Year). Typical vasovagal syncope as a "defense mechanism" for the heart by contrasting sympathetic overactivity. Clinical autonomic research : official journal of the Clinical Autonomic Research Society.
https://pubmed.ncbi.nlm.nih.gov/28669087/Alboni P, Brignole M, Degli Uberti EC (Year). Is vasovagal syncope a disease? Europace : European pacing, arrhythmias, and cardiac electrophysiology : journal of the working groups on cardiac pacing, arrhythmias, and cardiac cellular electrophysiology of the European Society of Cardiology.
https://pubmed.ncbi.nlm.nih.gov/17272328/