Systolic blood pressure values above 120 and diastolic blood pressure values above 80 are considered high, according to WebMD. Values between 120 and 139 for systolic, and 80 and 89 for diastolic blood pressure, indicate prehypertension. Values above 140 and 90, respectively, are indicative of hypertension, or high blood pressure.
Systolic blood pressure represents the pressure in the arteries when the heart is contracting, and the pressure when the heart is at rest is called diastolic blood pressure, WebMD states. Blood pressure is measured using a blood pressure cuff, which is wrapped around the upper arm, the forearm or the wrist.