Blood pressure is the pressure or force of blood exerted upon the walls of the arteries as the heart pumps out blood. Blood pressure is measured as systolic and diastolic. The normal value of blood pressure in adults is 120/80 mmHg (120-systolic, and 80-diastolic).
When the circulation of blood is too low to supply sufficient oxygen and nutrients to organs or tissues of the body, it is referred to as low blood pressure. Although low blood pressure is not a common cause of concern, if blood pressure is markedly low, it can produce many abnormal symptoms. Low blood pressure can be a result of various disorders, such as hemorrhage, endocrine disorders, dehydration, and cardiovascular diseases. There is no specific threshold for defining low blood pressure; it is considered too low when it produces abnormal symptoms. Usually, when it reaches below 90/60 mmHg, it is considered low blood pressure.
Conditions that reduce the volume of blood, reduce cardiac output (the amount of blood pumped by the heart), and medications are frequent causes of low blood pressure.