When I heard the U.S. was having a blood shortage during the pandemic, I decided to roll up my sleeve and donate for the first time. As I watched the second donation bag fill, I chatted casually with the technician and thought I’d soon be on my way.

And then, the sides of my vision began going dark, and the room in front of me faded. The technician immediately lowered the top half of my cot and raised my feet. He put cold compresses on my neck and tried to get me to stay alert with a conversation about my favorite foods.

The technician knew how to respond because fainting or near-fainting is a common experience during blood donation. Fainting is also common outside of blood drives, and many people will pass out at some point in their lives.

Scientists have a good understanding of why people pass out and what happens to the body when they faint. But where does the mind go when a person loses consciousness? The answer isn’t as straightforward.  

What Is Fainting?

Medical professionals refer to fainting as syncope, which describes a situation when a person loses consciousness due to a change in blood flow to the brain. With syncope, the person may lose consciousness anywhere from a few seconds to a few minutes. 

There are several types of syncope, and vasovagal syncope is most common among adults. About one-third of people will experience it once in their lifetime. For people 40 years and younger, vasovagal syncope is responsible for 85 percent of fainting spells. About 50 percent of fainting episodes among seniors are attributed to vasovagal syncope. 

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What Causes Fainting?

Fainting is often situational. A person might experience it because they have a change of blood pressure when they go from sitting to standing. Or it could be the result of the body coping with dehydration or ingesting toxins. It can also happen during medical emergencies such as acute blood loss, hemorrhaging or head injury.

Fainting can also be due to medical conditions such as cardiac arrhythmias, pulmonary embolism or seizures. 

Very commonly, fainting can be due to a psychological reaction in which a person has a flight-or-fight response that results in passing out. 

Read More: What is Anxiety and How Can Worries Overpower Us?

What Does Fainting Feel Like?

Vasovagal syncope during blood donation has been extensively studied due to the ongoing need for blood donors. Many potential donors are afraid of passing out, and only about five percent of eligible donors actually give blood.

When people have a vasovagal reaction during blood donation, their heart rate increases while their blood pressure drops. Less oxygen and blood go to the brain. They may experience dizziness, nausea or blurred vision. These symptoms can progress to passing out.

But fainting can also come from a psychological reaction to seeing the needle or the blood streaming through the tubing. This can also increase the person’s heart rate and lower their blood pressure. Again, this leads to less blood and oxygen getting to the brain, causing the person to pass out. 

Read More: The Connection Between Napping and High Blood Pressure

What Is it Like to Pass Out?

Many people who pass out report the same symptoms before fainting. They feel lightheaded or dizzy. They might feel sick to their stomach or suddenly feel warm. Many experience tunnel vision or see black patches. Some have ringing in their ears.

Before passing out, the person may seem pale to others, and they might sweat profusely. Depending on why a person passed out, they may regain consciousness almost immediately after fainting. In one case study, a person who passed out at a blood drive was estimated to be unconscious for less than 15 seconds. But in another example, a patient had an epileptic seizure on an airplane and was unconscious for about 15 minutes. 

Read More: What is Epilepsy and What Should We Know About it? 

Where Does the Mind Go When You Pass Out?

How a brain functions during syncope varies as greatly as the reasons why a person faints. For people who faint in response to an upsetting trigger, the process of slumping over in a chair or falling to the ground can lead to a better body positioning that helps adjust their blood pressure and heart rate.

In these instances, the person may be unconscious for mere seconds (assuming they didn’t harm themselves during the fall). They may not realize they lost consciousness and need a witness to tell them what happened.

In a 2011 study in EP Europace, study participants were placed on a table and then tilted to different angles to induce syncope. They were asked to describe their symptoms from different angles, and medical staff watched to see if they passed out.

If the person passed out, the researchers immediately changed the table position so the participant could regain consciousness. They asked questions like, ‘What happened to you?’ and ‘Did you pass out?’

Of the 387 participants, 159 lost consciousness. The fainters had an average age of 47.11 (range 16-87), and 71 percent were female. About a quarter of the participants age 60 and younger had immediate amnesia, meaning they weren’t sure or they denied fainting; half of participants age 60 and older had immediate amnesia.

The authors concluded that it’s common for people of all age groups to not even remember that they fainted. 

That was my experience during blood donation. I don’t know if I lost consciousness, but I do know I was able to complete my donation. Several weeks later, I received notification that my blood was sent for use in a trauma-one hospital in my county, making my donation feel worth the discomfort.

Read More: What Blood Types Can Reveal About Our Health