Why Did I Blackout?

Why did I black out?
If your blood pressure falls too low, the brain does not get enough blood, which makes you blackout (lose consciousness).

Why did I feel lightheaded or collapse ?
If the problem is less severe, you may just feel light-headed, vague, weak, unsteady, fall or collapse but not blackout.

Normal blood pressure control
The body normally keeps the blood pressure at the correct level all the time, including after standing up or after a meal. The blood pressure control system can increase the heart rate, pump the heart harder or narrow the blood vessels to keep the blood pressure correct.
 
Normal heart rate control
The body normally also keeps the heart rate at the correct rate all the time. It is normally faster when you exercise and slower when you are resting.

Problems with blood pressure and heart rate control
Sometimes the blood pressure and heart rate control systems do not work properly.

• Low blood pressure
  
  If the blood pressure falls too low, you may feel light headed, vague, weak, unsteady, fall, collapse or blackout.
  
  
• Heart rate too fast or too slow
  
  Sometimes the heart rate goes too slow or too fast, so the heart pump does not work effectively and the blood pressure drops.