Blood pressure is the force of blood pumping through the arteries. Each time the heart beats, pressure is created inside the arteries. Blood pressure is greatest when blood is moving out of the heart into the arteries. When the heart relaxes between beats (and blood isn't moving out of the heart), the pressure falls. Blood pressure becomes a health concern when it gets too high. Hypertension directly increases the risk of heart attack and stroke. Usually, hypertension has no signs or symptoms, so it's important to have it checked regularly by a health care provider. Measuring Blood Pressure Blood pressure is usually measured with a blood pressure cuff and stethoscope by a nurse or other health care provider. 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 is raised by the pressure of the blood. Levels of Hypertension The National Heart, Lung, and Blood Institute (NHLBI) has determined two levels of hypertension for adults. Stage 1: 140 mm Hg to 159 mm Hg systolic pressure over 90 mm Hg to 99 mm Hg diastolic pressure. Stage 2: 160 mm Hg or higher systolic pressure over 100 mm Hg or higher diastolic pressure. The NHLBI defines prehypertension as 120 mm Hg to 139 mm Hg systolic pressure over 80 mm Hg to 89 mm Hg diastolic pressure. The NHLBI guidelines define normal blood pressure as less than 120 mm Hg systolic pressure over less than 80 mm Hg diastolic pressure. A single elevated blood pressure measurement doesn't necessarily indicate a problem. A doctor will want to see multiple blood pressure measurements over several days or weeks before diagnosing hypertension and starting treatment. Who Hypertension Is Common In Nearly one-third of all Americans have hypertension, but it is particularly common in: People with diabetes mellitus, gout, or kidney disease African-Americans (particularly those who live in the southeastern United States) People in their early to middle adult years; men in this age group have higher blood pressure more often than women in this age group People in their middle to later adult years; women in this age group have higher blood pressure more often than men in this age group (more women have hypertension after menopause than men of the same age) Middle-aged and elderly people--more than half of all Americans age 60 and older have hypertension People whose parents or grandparents have/had hypertension Obese people Heavy drinkers of alcohol Women who are taking oral contraceptives Lifestyle Changes to Lower Hypertension Some simple lifestyle changes can help lower blood pressure--choosing foods that are low in sodium (salt), low in calories and fat, and high in starch and fiber; maintaining a healthy weight, or losing weight if overweight; limiting serving sizes; increasing physical activity; and reducing or stopping alcohol consumption. Some people will need to take daily medication to control hypertension. In addition, it's important for people with hypertension to get their blood pressure checked regularly and have close contact with their doctor.