Fainting is a temporary loss of consciousness that is spontaneously recovered after only a brief period of time. People usually lose consciousness because of a lack of blood flow and decreased oxygen to the brain. The cause can be related to a number of conditions or situations, some involving the heart, many not. The medical term for fainting is syncope (SIN-ko-pee).
People most often lose consciousness as the result of an abnormal circulatory reflex. Some people pass out at the sight of blood, in a crowded room, or even from excessive coughing. This is referred to as situational fainting and might affect a person repeatedly, but only in a very specific situation.
People may also black out when standing up after lying down. Referred to as postural fainting, this results from a decreased flow of blood to the brain, usually as the result of a drop in blood pressure. This can occur after significant blood loss, dehydration, or a change in cardiovascular medication, or as a side effect to other medications. Certain medical conditions, such as heart disease, diabetes, and migraine headaches, can also serve as a catalyst for fainting.
Most people who lose consciousness experience symptoms beforehand. These symptoms may include lightheadedness, blurred or “spotty” vision, dizziness, and weakness. People who observe someone about to pass out might notice paleness, sweating, and dilation of the pupils. In most situations, people who pass out regain consciousness within a moment or two.
Unless you and your healthcare provider are familiar with a condition that causes you to faint, such as with situational fainting, the condition is cause for a hospital visit. Blacking out can signal a serious underlying condition and should be evaluated by a doctor. The elderly, heart patients, and people who have any other accompanying symptoms should be transported to a hospital immediately. Even if you are aware of conditions that might cause you to lose consciousness, or if you are an otherwise healthy person with no prior episodes, you or a family member should still call your doctor after an episode.