What is blood pressure?


Blood pressure is the force of the blood pushing against the artery walls. The force is generated with each heartbeat as blood is pumped from the heart into the blood vessels. The size and elasticity of the artery walls also affect blood pressure. Each time the heart beats (contracts and relaxes), pressure is created inside the arteries.


The pressure is greatest when blood is pumped out of the heart into the arteries or systole. When the heart relaxes between beats (blood is not moving out of the heart), the pressure falls in the arteries or diastole.


Two numbers are recorded when measuring blood pressure. The top number, or systolic pressure, refers to the pressure inside the artery when the heart contracts and pumps blood through the body. The bottom number, or diastolic pressure, refers to the pressure inside the artery when the heart is at rest and is filling with blood. Both the systolic and diastolic pressures are recorded as "mm Hg" (millimeters of mercury). This recording represents how high the mercury column in the blood pressure cuff is raised by the pressure of the blood.


The National Heart, Lung, andBlood Institute (NHLBI) guidelines define normal blood pressure as follows:

  • Less than 120 mm Hg systolic pressure and less than 80 mm Hg diastolic pressure
  • 119/79 mm Hg or lower


What is high blood pressure (i.e. hypertension)?


High blood pressure, or hypertension, directly increases the risk of coronary heart disease (heart attack) and stroke (brain attack). With high blood pressure, the arteries may have an increased resistance against the flow of blood, causing the heart to pump harder to circulate the blood. Usually, high blood pressure has no signs or symptoms. However, you can know if your blood pressure is high by having it checked regularly by your health care provider.


The National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH) has determined two levels of high blood pressure, plus the range for pre-hypertension for adults:

  • Pre-Hypertension
    • 120-139 mm Hg systolic pressure and 80-89 mm Hg diastolic pressure
    • 120/80 – 139/89 mm Hg
  • Stage 1 Hypertension
    • 140-159 mm Hg systolic pressure and 90-99 mm Hg diastolic pressure 
    • 140/90 – 159/99 mm Hg
  • Stage 2 Hypertension
    • 160 mm Hg or higher systolic pressure and 100 mm Hg or higher diastolic pressure
    • 160/100 mm Hg or higher




How does blood pressure increase?


The following conditions are known to contribute to high blood pressure:

  • Being overweight/obese
  • Excessive sodium intake
  • A lack of exercise and physical activity


How is high blood pressure controlled?


High blood pressure can be controlled by:

  • Taking prescribed medications exactly as ordered by your health care provider
  • Choosing foods that are low in sodium (salt)Choosing foods high in potassium (especially fruits and vegetables)
    • Ages 2 and up (without high risk factors – 2,300 mg sodium per day
    • Ages 51+; African American; pre-existing high blood pressure, diabetes, or kidney disease – 1,500 mg sodium per day
  • Choosing foods low in calories and fat
  • Choosing foods high in fiber
  • Maintaining a healthy weight, or losing weight if overweight/obese
  • Limit serving sizes
  • Increasing physical activity
  • Reducing or omitting alcoholic beverages


For more information related to this topic, visit Healthy Living > Blood Pressure on Eat Right for Life.