could have a serious cause and it is good idea to see your doctor
for an evaluation. Fainting is caused by a drop in blood flow to the brain that results in a sudden, brief loss of consciousness. After you lose consciousness and fall or lie down, more blood can flow to your brain and you regain your consciousness. The most common causes of fainting are not serious. These are vasovagal reflex, which causes the heart rate to slow and the blood vessels to dilate and the result is that less blood goes to the brain. Some people have symptoms such as feeling weak, nauseated, hot, or dizzy beforehand. Orthostatic hypotension is another common cause. It occurs when you change position (i.e., standing up too fast, getting dehydrated, or taking certain medications) that triggers a sudden drop in blood pressure. However, there are some causes of fainting that can be serious if it happens often in a short period of time. These include heart or blood vessel problems (a blood clot in the lungs, an abnormal heartbeat, or heart disease) and nervous system problems such as seizure or stroke. Sometimes the cause is unknown. I recommend that you have your condition checked out by a primary care physician
who may refer you to a specialist.