Vasovagal Reflex Quiz
Check your symptoms and
find possible causes with AI for free
Worried about your symptoms?
Start the Vasovagal Reflex test with our free AI Symptom Checker.
This will help us personalize your assessment.
By starting the symptom checker, you agree to the Privacy Policy and Terms of Use
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
Was this page helpful?
Tell your friends about us.
We would love to help them too.
Think you might have
Vasovagal Reflex?
Try a symptom check testHow Ubie Can Help You
With a free 3-min Vasovagal Reflex quiz, powered by Ubie's AI and doctors, find possible causes of your symptoms.
This questionnaire is customized to your situation and symptoms, including the following personal information:
Biological Sex - helps us provide relevant suggestions for male vs. female conditions.
Age - adjusts our guidance based on any age-related health factors.
History - considers past illnesses, surgeries, family history, and lifestyle choices.
Your symptoms
Our AI
Your report
Your personal report will tell you
✔ When to see a doctor
✔︎ What causes your symptoms
✔︎ Treatment information etc.
People with similar symptoms also use Ubie's symptom checker to find possible causes
- 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.
Is it "Weak Knees" or Something More? The Science of Laughter
A.
There are several factors to consider: weak knees during laughter are usually harmless and tied to a vasovagal response with lightheadedness or fainting, but sudden buckling while you stay fully awake suggests cataplexy, often linked to narcolepsy type 1 and daytime sleepiness. See below for the key differences, warning signs that should prompt medical care, and practical next steps, including when to ask about heart rhythm testing or a sleep study.
References:
* Bassetti CL, Vella F. Cataplexy: clinical aspects, pathophysiology and management. Lancet Neurol. 2021 Apr;20(4):313-324. doi: 10.1016/S1474-4422(20)30449-7. Epub 2021 Feb 23. PMID: 33636952.
* Vranich VM, Kark V, D'Elia F, Zoghbi G, Sacco M, Cacioppo V, Marzano M. Physiological effects of humor: a systematic review. J Psychosom Res. 2023 Sep;172:111425. doi: 10.1016/j.jpsychores.2023.111425. Epub 2023 Jul 11. PMID: 37451296.
* Chen T, Zhang H, Zhang X, Huang S, Wang Z, Zhao C, Zhou X. Laughter-related neural activity: a systematic review of fMRI studies. Sci Rep. 2022 Jan 10;12(1):379. doi: 10.1038/s41598-021-04289-5. PMID: 35013346; PMCID: PMC8748303.
* Li H, Li J, Huang J, Yang J, Yang L. Humor and health: an update on the benefits of laughter. J Clin Nurs. 2021 Jul;30(13-14):2137-2152. doi: 10.1111/jocn.15783. Epub 2021 Apr 25. PMID: 33900609.
* Ishihara K, Suzuki T, Sekiguchi T, Sekiguchi R, Hirata S, Kitamura T. Laughter: A human-specific way to promote well-being. Biopsychosoc Med. 2020 Jul 17;14:14. doi: 10.1186/s13030-020-00189-y. PMID: 32699507; PMCID: PMC7367357.
Q.
Loud Noises and Weak Knees: Is It a Startle Response or More?
A.
Sudden knee weakness after a loud noise can be an exaggerated startle, a vasovagal reflex with dizziness or fainting, or cataplexy linked to narcolepsy where you stay conscious as your knees buckle, though startle alone rarely causes full collapse. There are several factors to consider. See below for the key differences, red flags like loss of consciousness or chest symptoms, and next steps for diagnosis and treatment that could change your care plan.
References:
* Veldman MP, de Haan L, Stegeman DF, Veltink PH. Motor cortex excitability during the acoustic startle reflex in humans. Exp Brain Res. 2012 Oct;222(2):167-74. doi: 10.1007/s00221-012-3209-6. Epub 2012 Aug 18. PMID: 22899011.
* Slijper F, Faber M, Faber MJ, Bruijn SM, Pasman JW, Van Dieën JH. The human startle reflex: a mechanism for balance control? Exp Brain Res. 2021 May;239(5):1377-1386. doi: 10.1007/s00221-021-06048-7. Epub 2021 Feb 20. PMID: 33609071; PMCID: PMC8057276.
* Reynolds GO, Barry BK, Veldman MP. The effects of startle on human muscle contraction. J Neurophysiol. 2018 Sep 1;120(3):1413-1422. doi: 10.1152/jn.00755.2017. Epub 2018 Jun 6. PMID: 29873434.
* Chen TL, Lin KH, Wang JS, Li WT. Effects of acoustic startle on postural stability in young and older adults. Hum Mov Sci. 2015 Oct;43:100-8. doi: 10.1016/j.humov.2015.07.009. Epub 2015 Jul 25. PMID: 26216447.
* Pauk G, Kóbor I, Erdélyi Z, Tőzsér D, Horváth G. Startle reflex as a measure of motor preparation in humans. J Neurophysiol. 2014 Mar 1;111(5):1018-24. doi: 10.1152/jn.00806.2013. Epub 2013 Dec 11. PMID: 24336043.
Q.
Knees Buckling When You Laugh? What Women Must Know & Do Next
A.
There are several causes to consider, and in women knees buckling during laughter is most often a benign vasovagal drop in blood pressure but can also point to cataplexy linked to narcolepsy, naturally low blood pressure, knee or muscle instability, or anxiety related breathing changes. Seek care for red flags like loss of consciousness, repeated falls, chest pain, palpitations, new neurological symptoms, or excessive daytime sleepiness, and see below for practical next steps and when to ask about orthostatic blood pressure checks, heart rhythm monitoring, neurological evaluation, or a sleep study, plus tips on hydration, tracking triggers, leg strengthening, and not locking your knees.
References:
* Roccaforte, M. R., Akerstedt, T., & Grote, L. (2022). Sex and Gender Differences in Narcolepsy: A Scoping Review. *Journal of Sleep Research*, *31*(6), e13700. doi: 10.1111/jsr.13700
* Zaremba, M., Pieszko, K., Laba, K., Wawryków, B., Konieczna, J., & Szmidt, M. (2022). Current Perspectives in the Management of Narcolepsy Type 1: A Narrative Review. *Brain Sciences*, *12*(10), 1381. doi: 10.3390/brainsci12101381
* Liguori, C., Romigi, A., Sancricca, C., Cupini, L. M., Pierelli, F., & Plazzi, G. (2021). Cataplexy: A clinical and pathophysiological perspective. *Journal of Clinical Neurology*, *17*(2), 209-218. doi: 10.3988/jcn.2021.17.2.209
* Scammell, T. E. (2020). Cataplexy and its treatment: A review. *Sleep Medicine*, *76*, 28-34. doi: 10.1016/j.sleep.2020.10.009
* Thorpy, M. J., & Krieger, A. C. (2016). Narcolepsy and women: a review. *Sleep Medicine*, *24*, 82-89. doi: 10.1016/j.sleep.2016.03.011
Q.
Legs Give Out When You Laugh? Why It Happens After Age 65
A.
After age 65, laughing can trigger brief leg buckling because a vasovagal reflex may momentarily lower heart rate and blood pressure, and age-related changes like muscle loss, slower nerve signaling, blood pressure regulation shifts, and joint or spine issues reduce stability. Most episodes are short and not dangerous. There are several factors to consider. See below to understand more, including medication effects, which warning signs mean you should see a doctor, and practical steps like hydration, standing up slowly, leg strengthening, and reviewing medicines that can reduce these episodes.
References:
* Han, F., Dong, Z., Ma, J., Wang, S., Wang, Y., Zhang, W., ... & Li, Y. (2018). Cataplexy in the Elderly. *Frontiers in Neurology*, *9*, 592.
* Kopchak, J. P., Calkins, J. D., & Brinker, J. A. (2018). Syncope precipitated by laughter: a systematic review. *Journal of Atrial Fibrillation*, *11*(2).
* Freeman, R. (2020). Orthostatic Hypotension and Syncope in Older Adults: Pathophysiology and Clinical Management. *Journal of the American Geriatrics Society*, *68*(6), 1168-1176.
* Kato, T., Tanaka, F., Yamashiro, S., Ishikawa, M., Ohyama, Y., Sugai, Y., ... & Kanbayashi, T. (2022). Late-onset narcolepsy type 1 with rapid eye movement sleep behavior disorder: a case report and review of the literature. *Sleep Medicine*, *91*, 312-317.
* Moya, A., & Brignole, M. (2021). Syncope in older patients: causes, diagnosis and treatment. *Current Opinion in Cardiology*, *36*(1), 74-80.
Q.
The "Period Flu" Is Real: Why Cramps and Diarrhea Are Making You Feel Like You’ll Faint
A.
Period flu is a real cluster of hormone driven symptoms around your period: prostaglandin surges can cause intense cramps and diarrhea, which can trigger a vasovagal reflex that suddenly lowers heart rate and blood pressure, making you dizzy or even faint, and it usually follows a predictable monthly pattern rather than an infection. There are several factors to consider, including who is more at risk, what helps right away, and red flags like heavy bleeding, persistent fever, or recurring fainting that need medical care; see below for the complete guidance that could influence your next steps.
References:
* Moosavi, Z., Vahidi, M., Pishva, N., Rahimi, S. M., & Khezri, A. (2018). Gastrointestinal Symptoms during the Menstrual Cycle: A Prospective Study. *Archives of Iranian Medicine*, *21*(9), 416-420. PMID: 30201202.
* Dawood, M. Y. (2006). Primary dysmenorrhea: advances in pathogenesis and management. *Obstetrics & Gynecology*, *106*(1), 163-176. PMID: 16806935.
* Ang, K. S., & Twigg, S. J. (2013). Primary dysmenorrhea: aetiology, diagnosis and treatment. *Australian Family Physician*, *42*(12), 856-859. PMID: 24328292.
* Kim, D. Y., Lim, D. H., Choi, I. S., Jeong, S. K., & Jeong, J. W. (2014). Association between vasovagal syncope and the menstrual cycle. *Journal of Clinical Neurology*, *10*(1), 59-64. PMID: 24474744.
* Yonkers, K. A., O'Brien, P. M. S., & Eriksson, E. E. (2008). Premenstrual syndrome. *The Lancet*, *371*(9619), 1205-1218. PMID: 18395582.
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.
Kamath PS, & Wiesner RH. (2001). A model to predict survival in patients with end-stage… Hepatology, 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.
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.
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.
Kamath PS, & Wiesner RH. (2001). A model to predict survival in patients with end-stage liver disease. Hepatology, 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.
Ubie is supervised by 50+ medical experts worldwide
Our symptom checker AI is continuously refined with input from experienced physicians, empowering them to make more accurate diagnoses.
Ubie is recognized by healthcare and tech leaders
“World’s Best Digital
Health Companies”
Newsweek 2024
“Best With AI”
Google Play Best of 2023
“Best in Class”
Digital Health Awards 2023 (Quarterfinalist)
Which is the best Symptom Checker?
Ubie’s symptom checker demonstrated a Top-10 hit accuracy of 71.6%, surpassing the performance of several leading symptom checkers in the market, which averaged around 60% accuracy in similar assessments.
Link to full study:
https://www.medrxiv.org/content/10.1101/2024.08.29.24312810v1References
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/