According to the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health, high blood pressure for adults is defined as:
140 mm Hg or greater systolic pressure
or
90 mm Hg or greater diastolic pressure
In an update of NHLBI guidelines for hypertension in 2003, a new blood pressure category was added called prehypertension:
120 mm Hg – 139 mm Hg systolic pressure
or
80 mm Hg – 89 mm Hg diastolic pressure
The NHLBI guidelines now define normal blood pressure as follows:
Less than 120 mm Hg systolic pressure
and
Less than 80 mm Hg diastolic pressure
These numbers should be used as a guide only. A single elevated blood pressure measurement is not necessarily an indication of a problem. Your doctor will want to see multiple blood pressure measurements over several days or weeks before making a diagnosis of hypertension (high blood pressure) and initiating treatment. A person who normally runs a lower-than-usual blood pressure may be considered hypertensive with lower blood pressure measurements than 140/