President Fords historic trip and fall down the steps of Air Force One. 1  People & Blogs. 2  Standard YouTube License.
The bottom number, called the diastolic pressure, is the measurement as the heart relaxes between beats. Normal blood pressure is a systolic pressure of less than 120 millimeters of mercury (mm Hg) and a diastolic pressure of less than 80 mm Hg, or 120/80 mm Hg, according to the American Heart Association (AHA). Having a blood pressure greater than 140/90 mm Hg is considered high blood pressure or hypertension. A blood pressure level between normal and hypertension, is called prehypertension, meaning it is higher than normal, but not high enough to be considered hypertension.
A blood pressure reading, given in millimeters of mercury (mm Hg), has two numbers. The first, or upper, number measures the pressure in arteries when the heart beats (systolic pressure). The second, or lower, number measures the pressure in arteries between beats (diastolic pressure). A systolic blood pressure reading of 90 mm Hg or less or a diastolic reading of 60 mm Hg or less is generally considered low blood pressure (hypotension). Normal blood pressure varies from person to person, though.