Vasovagal syncope happens when your body's normal ability to control blood pressure doesn't work like it should, causing you to pass out. Vasovagal syncope is the most common type of reflex syncope, which happens automatically for reasons you can't control.
Vasovagal syncope (pronounced “vay-so-vay-gal sin-co-pee”) happens when your blood pressure and heart rate drop suddenly, causing you to pass out or faint.
Vasovagal syncope is the most common type of reflex syncope, which happens automatically for reasons you can't control. It’s also sometimes called neurocardiogenic syncope because it's caused by factors involving the heart, brain or both.
One out of 3 people will experience vasovagal syncope at least once in their life, and it can happen to people of all age groups. In people under 40, vasovagal syncope causes about 85% of all passing out or fainting instances. In older adults, it makes up about half of those cases.
People with disorders that affect their autonomic nervous system, such as Parkinson's disease, are extremely unlikely to have vasovagal syncope. That's because their condition disrupts the normal functions of their nervous system.
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Vasovagal syncope is a reflex reaction to something happening around you, but the reflex is either too strong or happens at the wrong time. This all starts in your nervous system.
Part of your nervous system works without you having to think about it. This is called your autonomic (auto-nom-ick) nervous system, and it has two main subsystems:
Under normal circumstances, these two systems balance each other out. That balancing act involves reflexes that your body develops. Think of these reflexes like a computer program that tells different systems in your body, “If this happens, then you should do this.”
If your vagus nerve becomes too active, it can cause your heart rate and blood pressure to drop too much or too fast (or both). If your blood pressure drops too much, this causes an “attack” of vasovagal syncope, and you pass out because there’s not enough blood flow to your brain.
Most of the time, vasovagal syncope happens when you’re standing or sitting. It's rare for it to occur if you’re lying down. It is common with specific triggers like having your blood drawn.
A brief period right before vasovagal syncope may happen where you’re most likely to have symptoms. This period is called prodrome (rhymes with "dome") and is less common in older adults. Recognizing prodrome for vasovagal syncope can be a vital tool to help avoid injury.
Common symptoms that happen about 30 to 60 seconds before an attack include:
Once an attack starts, the following are likely to happen:
Once you come to, you’ll usually recover quickly (in about 20 to 30 seconds). Disorientation or confusion either doesn’t happen or they don’t last longer than 30 seconds. The following may also occur:
Vasovagal syncope is almost always triggered by something happening to you or around you. Common triggers include:
Two main types of reflex syncope are similar to vasovagal syncope. The main difference is the causes are easier to identify.
If you faint unexpectedly, you should receive emergency medical care right away. Serious or life-threatening conditions can cause syncope. A healthcare provider should examine you right away to determine if a more severe condition caused you to faint.
It's also essential to get medical attention after fainting if you hit your head (even only slightly). People who are on blood-thinning medications should always get medical attention after a fall because they have a much higher risk for internal bleeding.
Vasovagal syncope is almost never a life-threatening condition on its own. That’s because it’s caused by a reflex your body is supposed to have. The reflex is just happening too strongly or at the wrong time.
However, passing out without warning can cause injury — either from falls or depending on what you’re doing at the time. It’s also important to remember that many serious or life-threatening conditions can also cause you to pass out. If you don't have a history of passing out, it's crucial to find out why you passed out or rule out a more serious problem.
Your healthcare provider is likely also to ask questions about what might have caused your fainting. You should mention any recent changes in your health or unusual symptoms you’ve noticed, even ones that don’t seem important. These can help your provider accurately diagnose what caused you to faint.
Your healthcare provider may also run the following tests:
Most people who have vasovagal syncope will recover on their own, but some may need IV fluids (especially if they are dehydrated).
Other treatments that may be used include:
Many people who have vasovagal syncope can limit its impact on their lives, especially when they learn to recognize the symptoms of an attack. Your healthcare provider can help you learn more about the following:
Knowing what it feels like before you have an attack can allow you to sit or lay down so you're not hurt if you fall.
If you can recognize an attack before it happens, you may be able to stop it. Your healthcare provider can teach you techniques that keep your blood pressure high enough so that you don’t pass out. These include:
It's very common for people to only have vasovagal syncope once in their lifetime. However, some people with specific triggers may have vasovagal syncope for the rest of their lives. For people who have repeated attacks of vasovagal syncope, your healthcare provider can tell you more about what to expect with it.
You should talk to a healthcare provider if any of the following happen:
A note from Cleveland Clinic
Vasovagal syncope can disrupt your life and cause fear and anxiety. However, your healthcare provider can reassure you — and give you tips and resources. Their goal is to help you adapt to your condition, so you don’t have to stop living and enjoying your life.
Last reviewed by a Cleveland Clinic medical professional on 06/19/2022.
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