What Happens In Your Body When You Faint?

We’re not talking faking it for attention—it’s a real complex response from your body.

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Movies might romanticize a damsel in distress with a fainting spell, but what happens when you actually faint is less than dreamy. One minute you’re standing or sitting upright, and the next your eyes roll back into your head and you’ve hit the floor.

Some people lie still, but others shake while they are unconscious. This could be mistaken for a seizure. You might experience and even remember an intense dream from while you were out cold, even if it was only for a couple of seconds to minutes.

Then, you’ll come to—either on your own, or with the help of some smelling salts and a compress (probably with a crowd peering down at you). Likely, you’ll wonder, “How the heck did I get here?”

Here’s Why You Faint—and What Happens in Your Body

Fainting (also called syncope) occurs when your brain isn’t getting enough oxygen or nutrients. It could be due to an overreaction of the parasympathetic nervous system. This system in the body normally calms the body down by reducing blood pressure, heart rate, and breathing.

Normally, blood flow carries oxygen and nutrients to the brain. The brain needs this so it can function properly. What happens when that blood flow is suddenly reduced is that you may lose consciousness and faint.

The reasons for reduced blood flow aren’t always clear cut. However, it may be due to one of the following causes:

  1. A sudden movement (like standing up too quickly)
  2. A drop in blood sugar or blood pressure
  3. Dehydration (such as from working hard in the heat)
  4. Panic or hyperventilation (from fear, pain, or heavy breathing)
  5. Certain medications or substance use
  6. A drop in air pressure or being at a high altitude

What To Do As A Fainter—Before And After It Happens

Warning signs sometimes come before a fainting spell. These include feeling sweaty, dizzy, nauseated, and even having blurry or brightening vision. If you start to feel these symptoms, try your best to carefully sit with your head between your legs. Another option is to lie down and elevate your legs. This will help direct blood back towards your brain through gravity.

Another tip if you feel warning signs of a fainting spell is to move so you’re lower to the ground. This way, if you do faint, you won’t obtain an injury from falling onto a hard surface. In general, it’s really important to be in tune with and listen to your body. For example, if you’re at the gym, safely dismount from equipment right away if you are feeling lightheaded.

If you notice a pattern of fainting when you get hurt (or see someone else hurt), have blood drawn, or exercising, it's a good idea to always have a snack, water, or sugary drink on hand in your backpack or purse. Try to avoid getting up from being seated too quickly, and when you are getting shots or donating blood, let the provider know that you may faint so that it doesn't come as a surprise.

Occasional fainting is usually nothing to worry about, but you should talk to a doctor if it happens often or lasts more than a few minutes. There are some cases of more serious conditions that need to be addressed. Your doctor can run some tests and treat the underlying conditions causing you to faint.