When you faint, you do not respond to outside stimuli and your body goes limp. You may feel faint, dizzy or light headed just before you lose consciousness. A person with those symptoms is more likely to faint if he or she is standing upright. The person usually recovers spontaneously.
There are variations in the symptoms depending on what caused the fainting:
- If the fainting is caused by cardiovascular issues, the fainting usually begins and ends suddenly without warning. It is most often due to an arrhythmia. Other types of arrhythmias may cause fainting after or with heart palpitations.
- Fainting after an unpleasant physical or emotional shock such as being hurt, frightened or seeing blood. This type of fainting usually affects someone who is standing. Warning signs such as nausea, feeling weak, yawning, anxiety, blurring vision or swearing usually come on first.
- When blood pools in the legs either because a person has been standing motionless for a long time or in bed for a long time and then stands up, fainting can be triggered. This type of fainting can also occur because of severe varicose veins or certain types of drugs.
- Seizures may cause fainting. In this case, the unconsciousness is also accompanied by jerking muscles, convulsions, an inability to control the bladder or bowels or tongue biting. A person may feel confused when he or she regains consciousness.
Causes and Risk Factors
The most common cause of fainting is a sudden loss of blood flowing to the brain. This may be a result of any or a combination of the following:
- A reduction in the amount of blood being pumped out of the heart
- Certain drugs such as digitalis, calcium blockers and others
- Heart conditions such as sick sinus syndrome, ventricular tachyarrhythmias, aortic stenosis
- Heart rates that are either too low (fewer than 30 to 35 beats per minute) or too high (more than 150 to 180 beats a minute). Fainting may occur with less extreme heart rates if there is heart disease present.
- Irregular heart rhythms (arrhythmias) or electrical abnormalities in the pacing of the heart's beats
- Low blood sugar
- Lung disease
- Malfunction of a replaced heart valve
Older persons who have a greater risk of having heart or blood vessel disease are at a greater risk of fainting.