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Syncope is the medical term for fainting or losing consciousness. You may have fainted at some point in your life — after an injury, when you saw blood, when you received a shot, or when you were overheated. For many people, fainting on occasion isn’t a sign of a serious problem.

But sometimes, fainting is a warning that something else is going on. Some key signs let you know that you should talk to your doctor.

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What Happens When You Faint

Fainting happens when your blood pressure drops suddenly. Your brain doesn’t get enough blood flow, and you briefly lose consciousness. You need to lie down quickly or risk hurting yourself if you fall. Most people wake up quickly and start to feel better as blood flow is restored.

What Causes Syncope?

Often times, fainting isn’t caused by a serious condition. When it’s less serious, you usually have warning signs you’re about to pass out. You may feel hot, dizzy, nauseated, or weak and need to lie down. Stress, pain, fear, and holding your breath make your heart rate slow down, causing you to pass out. Dehydration and some medicines also can cause you to faint.

Sometimes, your blood pressure can drop when you stand up or change positions too fast. Blood collects in your lower body, and your brain briefly doesn’t get proper blood flow. While you may not have a serious underlying condition, it’s best to call a doctor if you pass out or nearly pass out when you stand quickly.

Whether it’s your first time passing out or it happens frequently, with or without symptoms, you should see your primary health care provider.

When to See a Doctor

For some people, fainting is a signal that something more serious is happening. Heart problems, stroke, or seizure can cause you to pass out. When it’s more serious, you may not have warning signs, such as nausea or dizziness, before you pass out. Syncope during exercise may be a sign of a more serious heart condition.

Fainting can signal heart disease, heart valve issues, a blood clot in the lungs, or an abnormal heartbeat (arrhythmia).

Other warning signs that should prompt you to call your doctor are:

  • Shortness of breath.
  • Chest pain.
  • Heart racing or palpitations.
  • Frequent fainting.
  • Fainting when sitting or lying down.

Fainting from heart conditions becomes more common with age. Occasional fainting from a known stimulus, such as seeing blood, may not be cause for concern. However, low blood pressure (hypotension) and other heart problems need treatment. You should see a doctor if you faint without warning or have other signs of a problem.

If you’re unsure whether fainting could be a sign of a serious problem, make an appointment with your doctor.

About Heart and Vascular Institute

The UPMC Heart and Vascular Institute has long been a leader in cardiovascular care, with a rich history in clinical research and innovation. As one of the first heart transplant centers in the country and as the developer of one of the first heart-assist devices, UPMC has contributed to advancing the field of cardiovascular medicine.