Fainting is pretty common in teens. The good news is that most of the time it's not a sign of something serious.

What Is Fainting?

Fainting is a temporary loss of consciousness. It happens when there isn't enough blood going to the brain because of a drop in blood pressure.

Why Do People Faint?

Blood pressure can drop from dehydration, a quick change in position, standing or sitting still for a long period, or a sudden fear of something (such as the sight of blood).

Here are some of the common reasons for fainting:

Physical triggers. Getting too hot or being in a crowded, poorly ventilated setting are common causes of fainting. Sometimes just standing for a very long time or getting up too fast after sitting or lying down can cause someone to faint.

Emotional stress. Emotions like fright, pain, anxiety, or shock can cause to drop. This is the reason why people faint when something frightens or horrifies them, like the sight of blood.

Hyperventilation. A person who is hyperventilating is taking fast breaths. Carbon dioxide (CO2) levels in the blood falls, causing blood vessels to narrow. Blood flow to the brain decreases, making a person faint.

Medical conditions. Conditions such as heart problems, anemia, low blood sugar, or postural orthostatic tachycardia syndrome (POTS) can cause fainting. 

Pregnancy. During pregnancy, the body undergoes a lot of changes, including changes in the circulatory system. These may cause a woman to faint. And as the uterus grows, it can press on and partially block blood flow through large blood vessels, which can decrease blood supply to the brain.

What Are the Warning Signs of Fainting?

Someone who is about to faint might have:

• dizziness
• lightheadedness
• paleness
• unsteadiness
• vision changes
• fast or irregular heartbeat
• sweating
• nausea and/or vomiting

Can Fainting Be Prevented?

If you think you're going to faint, you can try to stop it by taking these steps:

• If possible, lie down. This can help prevent a fainting episode, as it lets blood get to the brain, especially if the feet are propped up a bit. Be sure to stand up again slowly when you feel better — move to a sitting position for several minutes first, then to standing.
• Sit down with your head lowered forward between your knees. This will also help blood get to the brain, though it's not as good as lying down. When you feel better, move slowly into an upright seated position, then stand.
• Don't let yourself get dehydrated. Drink enough liquids throughout the day. Drink plenty of fluids before, during, and after exercise and in hot weather.
• Keep blood circulating. If you have to stand or sit for a long time, take breaks often and move around. Regularly tense your leg muscles or cross your legs to help improve blood flow.
• Avoid overheated, cramped, or stuffy environments, whenever possible.

When Should I Call the Doctor?

If you've only fainted once, it was brief, and the reasons why are obvious (like being in a hot, crowded setting), then there's usually no need to worry about it. But if you have a medical condition or are taking prescription medicines, it's a good idea to call your doctor.

Call the doctor or get medical care if you:

• hurt yourself when you fainted (for example, if you banged your head really hard)
• have chest pain, palpitations (fast or irregular heartbeats), or shortness of breath
• had a
• fainted during exercise or other physical activity
• have fainted more than once

The doctor will ask a few questions, do an exam, and might order some tests, such as:

• an EKG (a type of test for heart problems)
• a blood sugar test
• a blood test to check for anemia

How Can I Help Someone Who Faints?

If you're with someone who has fainted, try to help the person lies down. Don't move someone who might be injured from falling (that can make things worse). Instead, loosen any tight clothing — such as belts, collars, or ties. Propping the person's feet and lower legs up on a backpack or jacket also can help blood flow to the brain.

Someone who has fainted will usually recover quickly. Because it's normal to feel a bit weak after fainting, be sure the person stays lying down for a bit. Getting up too soon may bring on another fainting spell.

Call 911 if someone who has fainted:

• does not regain consciousness after a few minutes
• passed out while exercising
• is having chest pain, trouble breathing, or a seizure