Fainting Symptoms: Before, During & After

How to Know You're About to Pass Out


Fainting (syncope) is a sudden loss of consciousness from a lack of blood flow to the brain. Patients usually wake up quickly after collapsing. Although fainting is defined as a sudden loss of consciousness, the moments leading up to actually passing out will probably have several signs and symptoms that the victim is about to faint.

Signs and Symptoms You're About to Faint

Before fainting, a patient can exhibit or feel all or some of these signs and symptoms, depending on the cause of fainting:

In cases of fainting caused by stimulation of the vagus nerve (the most common type of fainting), patients might have cramps or an urge to have a bowel movement right before they pass out.

How Fainting Looks

In cartoons, fainting is always done by falling over stiff as a board and landing either flat on your face or back. In movies, the classic melodramatic faint was with a gasp, a hand to the forehead and collapsing into the arms of the nearest male heartthrob.

In real life, fainting ranges from subtle to violent. As the brain stops getting enough blood flow to stay conscious, it stops sending out signals to the muscle cells. The muscles lose their tone and the body just collapses into whatever heap gravity pulls it to.

Occasionally, that sudden exit of blood from the brain leads to a little nervous impulse—kind of like static through a phone line. It may result in a bit of a tremble or shake. Sometimes it looks like a shudder; sometimes it looks like a seizure (albeit very short). Ever felt an involuntary jerk in your arms or legs just as you fall asleep?

That is called a myoclonic contraction, and it's exactly the same type of twitch some fainting patients exhibit. While a myoclonic contraction is not a seizure, true seizures can also cause a sudden loss of consciousness. However, the symptoms of a seizure are different. So is the treatment of seizures.

Symptoms After Fainting

Once the person goes from vertical to horizontal, blood starts flowing back into the brain and they begin to wake up. It can be quick or it can take a while; everybody's different.

Here are some of the more common symptoms that can occur after fainting:

  • sweating stops
  • color begins to return
  • rapid pulse or "racing heart"
  • loss of bowel or bladder control (incontinence)


Probst, M., Kanzaria, H., Gbedemah, M., Richardson, L., & Sun, B. (2015). National trends in resource utilization associated with ED visits for syncope. The American Journal Of Emergency Medicine33(8), 998-1001. 

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