Fainting is a brief loss of consciousness that happens when the brain suddenly does not get enough blood and oxygen for a short time.

Basic definition

Medically, fainting is called syncope, and it usually lasts from a few seconds to a couple of minutes, with most people waking up quickly and fully. During a faint, blood pressure and blood flow to the brain drop, leading to collapse and temporary unresponsiveness.

Common signs and symptoms

Before fainting, many people feel warning signs such as dizziness, light- headedness, nausea, sweating, blurred or “tunnel” vision, weakness, or a feeling of warmth. While fainted, the person is usually pale, floppy or slumped, unresponsive for a short time, and then recovers, often feeling tired or shaky.

Typical causes

Common triggers include standing up too quickly, dehydration, heat, pain, seeing blood, strong emotions like fear or distress, not eating or drinking enough, or low blood pressure. More serious causes can involve heart rhythm problems, heart disease, stroke, or certain medicines, which is why repeated or unexplained fainting should be checked by a doctor.

When to seek help

Medical help is important if fainting happens often, happens during exercise, is associated with chest pain or shortness of breath, or if recovery is slow or incomplete. Emergency care is needed if someone faints and has possible stroke signs, a severe injury from the fall, or does not wake within a couple of minutes.