When Is Blood Pressure Classified As "too High"?

A sustained systolic reading of at least 160 millimeters of mercury or a diastolic reading of at least 100 millimeters of mercury indicates high blood pressure, also called stage 2 hypertension, according to Mayo Clinic. Stage 2 hypertension is a more severe form of the condition.

If systolic pressure measures between 140 and 159 millimeters of mercury, or diastolic measures between 90 and 99 millimeters of mercury, the patient is diagnosed with stage 1 hypertension. With prehypertension systolic pressure measures between 120 and 139 millimeters of mercury, or diastolic pressure ranges between 80 and 89 millimeters of mercury. Normal blood pressure is 120/80 millimeters of mercury, according to Mayo Clinic.