Diseases & Conditions

Blood Pressure Test


Overview & Description

Blood pressure is expressed in millimeters of mercury, or mm Hg. The systolic blood pressure is the top number of a blood pressure reading. This shows the maximum pressure in the blood vessels as the heart contracts and circulates blood throughout the body. The diastolic blood pressure is the bottom number of a blood pressure reading. It shows the lowest pressure in the blood vessels between heartbeats, when the heart is at rest.

How is the test performed?

A person is seated with his or her bare arm resting on a table. The arm is bent at the elbow so that it sits at the same level as the heart. A blood pressure cuff is placed on the upper arm and inflated. A technician wearing a stethoscope listens carefully as air is slowly let out of the cuff. He or she notes the systolic and diastolic pressures. Systolic pressure is the blood pressure at the time the heart is contracted. Diastolic pressure is the blood pressure at the time the heart is relaxed.


Preparation & Expectations

What is involved in preparation for the test?

No preparation is needed for a blood pressure reading.


Results and Values

What do the test results mean?

High blood pressure is defined as a systolic blood pressure reading greater than 140 mm Hg or a diastolic blood pressure reading greater than 90 mm Hg.

The National Institutes of Health has further defined high blood pressure. These categories are for people 18 years and over, who are not taking medication for high blood pressure and who do not have a short-term serious illness. These categories are as follows:

  • Normal blood pressure is a systolic pressure under 130, and a diastolic pressure under 85.
  • High normal blood pressure is a systolic pressure of 130 to 139, and a diastolic pressure of 85 to 89.
  • Stage 1 high blood pressure is a systolic pressure of 140 to 159, and a diastolic pressure of 90 to 99.
  • Stage 2 high blood pressure is a systolic pressure of 160 to 179, and a diastolic pressure of 100 to 109.
  • Stage 3 high blood pressure is a systoliC pressure of 180 or above, or a diastolic pressure of 110 or above.

  • Attribution

    Author:David T. Moran, MD
    Date Written:
    Editor:Ballenberg, Sally, BS
    Edit Date:05/31/01
    Reviewer:Eileen McLaughlin, RN, BSN
    Date Reviewed:09/25/01