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Understanding My Blood Pressure Test

Organs impacted by high blood pressure

Blood pressure is measured in millimeters of mercury (mm Hg). The classifications in the table below are for people who aren't taking antihypertensive (blood pressure-lowering) drugs and aren't acutely ill.

When a person's systolic and diastolic pressures fall into different categories, the higher category is used to classify the blood pressure status. Diagnosing high blood pressure is based on the average of two or more readings taken at each of two or more visits after an initial screening.

Classification of Blood Pressure

for Adults Age 18 Years and Older


CATEGORY SYSTOLIC (mm Hg) DIASTOLIC (mmHg)
Normal* less than 120 and less than 80
Prehypertension 120 - 139 or 80 - 89
Hypertension: Stage 1 140 - 159 or 90 - 99
Hypertension: Stage 2 160 or higher or 100 or higher

*Unusually low readings should be evaluated for clinical significance.

Above content provided by The American Heart Association in partnership with Beth Israel Deaconess Medical Center. For advice about your medical care, consult your doctor.

Posted September 2010

Contact Information

CardioVascular Institute at
Beth Israel Deaconess Medical Center
330 Brookline Avenue
Boston, MA 02215
888-99-MYCVI
617-632-9777

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