Fainting (temporary loss of consciousness)

Fainting is a temporary loss of consciousness. Fainting may not be serious. A sudden emotional upset may cause you to faint. If you recover immediately and do not faint again, the fainting episode usually is not serious.

However, fainting can be a sign of a serious health problem, such as bleeding. Most of the time when bleeding is present, the need to seek medical care is obvious. However, sometimes bleeding is not obvious (occult bleeding). Small amounts of bleeding may occur over days or weeks without being noticed. When this is the case, lightheadedness, fatigue, and fainting may be the first noticeable symptoms of blood loss. If you faint, look for signs of bleeding, such as:

• Bloody or pink urine that is not related to either menstrual blood in the urine or to dietary factors.
• Heavy or prolonged vaginal bleeding (saturating more than 8 pads or super tampons in an 8-hour period).
• An increase in the number and severity of bruises.
• Rectal bleeding or blood in the stool.
• Several unexplained nosebleeds.

Fainting can have other serious causes, such as:

• Heart rhythm problems (arrhythmias).
• Loss of blood flow to the brain with a transient ischemic attack (TIA).
• A nervous system problem, such as a seizure.
• A drop in blood sugar levels (hypoglycemia).
• A toxic effect from a medicine or a street drug.

Another serious health problem may be present if you become lightheaded or faint every time you stand up. If this happens just a few times, it may just be that you sat too long and blood pooled in your legs (orthostatic hypotension). Ongoing fainting needs to be checked by your doctor.