When you faint, here's what's really happening

Fainting, also known as syncope, is when you have a drop in blood flow to the brain, which causes temporary unconsciousness (via MedlinePlus). You might have a medical condition that causes fainting, or you might not know why you fainted in the first place. 

Some of the most common causes of fainting include vasovagal syncope, abnormal heart rhythm, or orthostatic hypertension, according to Harvard Health Publishing. However, 75 percent of the time, there is no serious cause for fainting, but you could injure yourself when you fall due to fainting. It's important to get checked out if you faint so you can rule out any serious medical condition and make sure you didn't hurt yourself when you fell. Usually, when you faint, you are only unconscious for a few minutes. 

Some medical conditions that can cause fainting include hypoglycemia, seizures, irregular heartbeat, and anemia. Fainting sometimes runs in families (via WebMD). Most of the time, no serious medical cause is to blame, and you'll be sent home with advice to come back if it happens again. 

What happens when you faint

There are three causes of fainting that are the most common. 

Vasovagal syncope: With vasovagal syncope, your vagal nerve increases its activity, causing your heart to slow down and blood vessels to open up. This leads to a decrease in blood pressure and reduced blood flow to your brain. Vasovagal syncope can be caused by an emotional trigger, such as feeling afraid, and a warm environment doesn't help. Even forceful coughing or straining during a bowel movement can cause this. 

Abnormal heart rhythm: If your heart beats too slow or too fast, your blood pressure might drop, causing a decrease in blood flow to your brain and fainting. The cause of an abnormal heart rhythm could be an overactive thyroid gland, certain medications, or heart disease. 

Orthostatic hypertension: Orthostatic hypertension is the medical term for a drop in blood pressure when you stand up from lying down or sitting. You have probably felt a mild version of this before when you stand up too fast and feel dizzy, and you have to pause for a moment before going about your business. This can be caused by certain medications, drugs, alcohol, dehydration, or blood loss. Orthostatic hypertension is more common as you age. 

No matter the cause, if you faint, it's best to get checked out to make sure it's not something that needs medical attention.