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Blood pressure refers to the force exerted by circulating blood on the walls of blood vessels, and constitutes one of the principal vital signs. The term blood pressure generally refers to arterial pressure, the pressure in the larger arteries; arteries being the blood vessels which take blood away from the heart. Your heart beats about 60 to 80 times a minute under normal conditions. Your blood pressure rises with each heartbeat and falls when your heart relaxes between beats. Your blood pressure can change from minute to minute, with changes in posture, exercise or sleeping, but it should normally be less than 120/80 mm Hg (millimeters of mercury) for an adult. Blood pressure that stays between 120–139/80–89 is considered pre-hypertension and above this level (140/90 mm Hg or higher) is considered high (hypertension). Your doctor may take several readings over time before deciding whether your blood pressure is high.

It is important to understand what the two numbers mean:

• The higher (systolic) number represents the pressure while the heart is beating.
• The lower (diastolic) number represents the pressure when the heart is resting between beats.
• The higher (systolic) number is always stated first and the diastolic pressure second. For example: 118/76 (118 over 76); systolic = 118, diastolic = 76.

Additional Resources:

http://www.americanheart.org/presenter.jhtml?identifier=2112

http://edis.ifas.ufl.edu/pdffiles/HE/HE69600.pdf

http://edis.ifas.ufl.edu/pdffiles/FY/FY30500.pdf