Fainting Symptoms and Causes

Fainting (syncope) is a sudden loss of consciousness from a lack of blood flow to the brain. People who have passed out usually wake up quickly after collapsing, but in some cases, fainting is a sign of a serious or potentially life-threatening condition.

It's not unusual for people to experience symptoms of dizziness or nausea, and feel as if they might pass out without fully losing consciousness, too. While a person may recover quickly by lying flat, it's important to be sure the underlying cause of their syncope is identified.

This article explains the symptoms of fainting and many possible reasons why it can happen. It details diagnosis and treatment options, and offers some tips on how fainting may be prevented.

What Fainting Feels Like

Fainting tends to affect younger people, although heart conditions and drug interactions often lead older people to pass out.  There's a high incidence in people between the ages of 10 and 30 years, and then again in those ages 65 and older. It's generally less common in middle-aged adults.

Most people will suddenly feel flushed and warm, become weak, and lose consciousness. When they do, they pass out and often fall (which can lead to additional injuries). Other signs and symptoms include:

• Confusion
• Dizziness or feeling lightheaded
• Headache
• Nausea
• Shortness of breath
• Cold sweats
• Trembling or shaking
• Tunnel or blurred vision
  
• Weakness

Stimulation of the vagus nerve is one cause of fainting spells. The vagus is the largest nerve in the body, running from the brain to the abdomen, and it affects multiple systems (like heart rate and blood pressure) when stimulated. This can have a number of causes, including pain or stress.

Causes of Fainting

The cause of fainting can be as simple (and temporary) as anxiety that causes hyperventilation (breathing too fast) or heat illness from working hard in the sun. But fainting can also be a symptom of a sudden and lethal heart condition.

Heart-Related Causes

Serious heart conditions that can cause syncope include:

• Abnormal heart rhythms and heart rates
• An aortic dissection (tear) in an artery that carries blood away from the heart
• Aortic stenosis (valve blockage)

If the heart beats too fast or too slow, it can't keep the blood pressure up as high as it needs to be. Blood drains from the brain and leads to fainting. During a heart attack, the heart muscle can become too weak to maintain blood pressure.

Dehydration

Too little water in the bloodstream lowers blood pressure, and stimulating the vagus nerve when the system is already low can lead to dizziness and fainting.

There are many causes of dehydration, including vomiting or diarrhea. Vomiting and diarrhea, specifically, are related to vagus nerve function.

Shock

Shock is a condition characterized by low blood pressure that often leads to a loss of consciousness and very low blood pressure.

Shock is a life-threatening emergency that usually comes from bleeding but can also result from severe allergy (anaphylaxis). Severe infection can lead to shock. People with shock will most likely become confused, and then lose consciousness as their condition gets worse.

Illicit Drugs or Alcohol

Alcohol misuse and substance abuse can cause people to pass out. Besides its obvious sedation effect, alcohol makes people urinate, which will eventually lead to dehydration. It also dilates blood vessels, which decreases blood pressure.

Like shock, losing consciousness due to alcohol is not technically considered fainting, but it may or may not be cause for concern. It is possible to die from alcohol poisoning, and passing out is a sign of serious intoxication.

Drug Interactions

Some medications can increase the risk of passing out, whether taken alone or when interacting with other drugs and supplements. They include:

• Any drug meant to control high blood pressure, since it lowers blood pressure
• Diuretics like Lasix (furosemide) that make you urinate and can lead to dehydration
• Beta blockers and other heart drugs
• Nitrates (a vasodilator) that quickly lowers blood pressure
• Tricyclic antidepressants like amitriptyline
• Opiates, which slow breathing while lowering blood pressure

One study of people diagnosed with type 2 diabetes found the risk of a syncopal episode (passing out) was higher in those taking several medications (polypharmacy). Be sure to talk with a healthcare provider to limit the risk.

Less Common Causes of Passing Out

Some people pass out when they see blood, which is caused by a vasovagal response. Or, they may faint when donating blood or during a vaccination as they're getting a shot. Anxiety, panic disorder, and stress can stimulate the vagus nerve and lead to a loss of consciousness.

Some people (commonly males) can pass out when they urinate (micturition syncope). The exact cause is not understood but may be related to vagal response. It can occur with coughing or stretching, too.

When Kids Are Passing Out

Fainting episodes affect up to 25% of children and teens, too, and typically for the same reasons that they occur in younger adults: Heat exposure, dehydration, and hyperventilation are common. But some other causes are unique to kids, like holding their breath during temper tantrums.

Experts increasingly warn of social media influences inviting teens to play "pass out," "blackout," or the "fainting game." Headaches and bloodshot eyes are common in kids playing these potentially fatal games.

When to See a Healthcare Provider

By itself, fainting is not life-threatening. However, some dangerous conditions can cause people to faint and they should be evaluated by a healthcare provider. You should see a healthcare provider if you pass out and experience other symptoms including:

• Chest pain
• Trouble breathing
• Heart rhythm changes
• Changes in vision, like blurring
• Mental confusion
• Difficulty speaking

In some cases, sudden episodes of fainting can occur when you turn your head to the side. This can be due to pressure on the carotid artery that changes blood flow. It also can be related to health conditions like carotid artery stenosis (blockage).

If someone faints but doesn't wake up within a few seconds, seek medical care.

Diagnosis and Treatment

Treatment for a condition that causes fainting will depend on the underlying cause. Your healthcare provider will rely on a full medical history and physical assessment. They also may order tests that include an electrocardiogram (12-lead EKG) to check heart rhythm.

A Holter monitor test (ambulatory EKG) may be used to see how your heart rhythm changes as you perform normal daily functions for a day or two. In addition to heart function, your provider will look to see if there's a neurological cause or a metabolic disorder that's responsible for fainting episodes. You may need blood work, glucose testing, or other assessments.

You also may need further evaluation and specialist care, depending on the results. Treatment will be determined by the diagnosis and can range from simple stress management techniques to cardiac surgery and rehabilitation.

Prevention

Sometimes, there's absolutely nothing you can do to stop from fainting. But if you feel an episode coming on, you can move your body in specific ways to prevent fainting. You can:

• Make a fist.
• Cross your legs.
• Squeeze your thighs together.
• Tighten the muscles in your arms.
• Lie down or put your head between your knees.

If the feeling doesn't pass in a few minutes, or you begin to experience chest pain or shortness of breath, call 911.

To prevent passing out in the long term, you need to avoid situations that can lead to episodes, like alcohol misuse or forgetting to eat and drink. You should also try to maintain a healthy lifestyle, keep up with your healthcare appointments, and take medications as prescribed.

Summary

Fainting is a sudden loss of consciousness from a lack of blood flow to the brain. It can be caused by many things, including dehydration, shock, too much alcohol, and even anxiety. While a fainting spell usually doesn't last for long, it can be associated with a life-threatening event like a heart attack.

People who have experienced multiple fainting spells should see a healthcare provider to learn the cause. Certain tests, like a tilt table test, can help with diagnosis and treatment of syncope.