The 3 Most Common Reasons For Passing Out

Photographed by Alexandra Gavillet.
Fainting seems ridiculously old-fashioned (overly tight corset, anyone?) but the truth is, as weird as it is, passing out is actually not that unusual — even among healthy, non-corset-wearing people. And when it happens, it can be pretty freaky, whether you're the fainter or you see someone else pass out.
"Passing out is super common, and we see young, healthy people passed out all the time," says Christopher Tedeschi, MD, a professor of emergency medicine at Columbia University Medical Center. "And it's almost always a not dangerous event."
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Fainting happens when your brain isn't getting enough blood. And there are some cases that aren't totally harmless. A good gauge is the amount of time: Although your friend can recover easily after being passed out for a minute or two, you should be more worried if they're taking longer to come out of it. "That's not garden-variety passing out," Dr. Tedeschi says.
Also, if you've passed out after a workout, Dr. Tedeschi says that's definitely reason for further investigation. It could be due to one of many rare (but serious) underlying heart conditions, which are often inherited.
In all cases, though, a major worry is whether or not you injure yourself on your way down — especially your head. For that reason, and because it's hard to tell whether or not your fainting episode is due to something serious, you should always get checked out by a doctor after you pass out (especially if it's the first time).
But to put you at ease, here's what you need to know about the most common reasons for passing out — and why you probably don't need to worry.
1. Your blood pressure dropped (orthostatic hypotension): Ever stand up too fast and feel a little woozy? In some cases, that drop in blood pressure can actually make you faint because it makes it harder for blood to get to your brain. Skipping meals, being dehydrated, drinking alcohol, and being sick can all make you more vulnerable to this usually-harmless kind of fainting, Dr. Tedeschi says. During pregnancy, changes in blood pressure and morning sickness-related dehydration can also make this type of passing out more likely.
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So maybe you ran out the door in a rush and forgot your breakfast. Or perhaps you've been out in the sun all day and haven't exactly been drinking that much water. In those cases, it's pretty easy to look back on your day and figure out why you fainted (and how to prevent it in the future).
2. You're really, really nervous (vasovagal syncope): This is the classic "I pass out at the sight of blood" situation, Dr. Tedeschi says. In reality, it's just a reflex controlled by your body's vagus nerve, which helps regulate your heart rate. "When you get a little anxious or excited or revved up about something, your body counteracts that," he explains. "And when your body overcompensates, your heart slows down." From there, it's the same story: Your body can't pump enough blood to your brain, and you pass out. Again, this isn't usually a sign that something more serious is going on, but it's hard to tell without getting checked out by a doctor.
3. You've got an underlying health issue: "Once in a blue moon, we encounter young, healthy people with heart problems that cause them to pass out," Dr. Tedeschi says. These are usually issues with the heart's rhythm, such as Brugada syndrome, which can be quite serious. In other cases, an infection or internal bleeding can cause your blood pressure to drop and, therefore, faint.
So if you can trace your fainting to a specific cause that you've encountered before (e.g. dehydration or watching your blood get drawn), then Dr. Tedeschi says it's not an emergency situation. If you pass out and have other symptoms (such as chest pain or shortness of breath), you're sick with an infection, or you were just working out, you should definitely get yourself some medical attention. But again, it's worth checking in with your doctor to make sure there's nothing else going on. And, no, splashing cold water does nothing.
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