Hypotension is defined as blood pressure that is below the normal expected for an individual in a given environment. Hypotension is the opposite of hypertension, which is abnormally high blood pressure.
When blood pressure drops below a certain level, oxygen and other nutrients are not efficiently delivered to the brain. This can lead to dizziness and fainting or be an indication of other serious conditions. Severely low blood pressure can lead to a life-threatening condition called shock.