For a normal reading, your blood pressure needs to show a top number (systolic pressure) that’s between 90 and less than 120 and a bottom number (diastolic pressure) that’s between 60 and less than 80. The American Heart Association (AHA) considers blood pressure to be within the normal range when both your systolic and diastolic numbers are in these ranges.
A blood pressure reading measures both the systolic and diastolic forces, with the systolic pressure listed first. The numbers show your pressure in units of millimeters of mercury (mm Hg)—how high the pressure inside your arteries would be able to raise a column of mercury. For example, a reading of 120/80 mm Hg means a systolic pressure of 120 mm Hg and diastolic pressure of 80 mm Hg.
"The recommendations are neither a policy nor a prescription for physicians," says Claude Lenfant, MD, director of the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health. "Nobody is advocating some sort of cookbook medicine. The physician will have to decide whether this medication or that medication is the best depending on many considerations."
There are a number of factors that likely work together to cause high blood pressure. A family history of high blood pressure can make you more likely to develop the condition, so genetics likely plays a role. High salt intake (too much salt in the diet) or salt sensitivity occurs in some people, which can lead to hypertension, particularly in the elderly, African Americans, people who are obese, or people with chronic kidney (renal) disease.
Unlike high blood pressure symptoms, which are poorly defined and often totally absent, low blood pressure symptoms tend to be more upfront and easily recognizable. The development of symptoms is often a warning sign of a potentially serious underlying disorder. Generally speaking, your blood pressure would need to fall pretty dramatically before symptoms develop.