Your health care professional should check your blood pressure at least once every two years, and more often if it's high. A high blood pressure diagnosis is usually based on at least the average of two or more readings per visit, taken at two different visits after an initial screening.

The only way to properly check your blood pressure is to measure it with a device called a sphygmomanometer, commonly called a blood pressure cuff. This is a quick and painless test in which a rubber cuff is wrapped around your upper arm and inflated. As the cuff inflates, it compresses a large artery, stopping the blood's flow through that artery. When your health care professional releases the air in the cuff, he or she can listen with a stethoscope for the blood to start flowing through your artery again. Your health care professional can watch the sphygmomanometer gauge to determine systolic pressure -- the pressure when the first sound of pulsing blood is heard -- and the diastolic pressure, the pressure when the last sound of pulsing blood is heard.

In May 2003, the NHLBI released new clinical practice guidelines for the prevention, detection and treatment of high blood pressure. The guidelines feature altered blood pressure categories, including a new "prehypertension" level, which covers about 22 percent of American adults, or about 45 million people.

This new category alerts you to your real risk of high blood pressure. A study in the journal Stroke finds that people with prehypertension have three times the heart attack risk of people without hypertension. You don't need medication therapy, unless you have another condition like diabetes or chronic kidney disease. However, you should make any necessary lifestyle changes, such as losing excess weight, becoming physically active, limiting alcohol consumption and following a heart-healthy eating plan, including cutting back on salt and other forms of sodium, to reduce your blood pressure levels.

Readings at or above 140 systolic or 90 diastolic are considered hypertensive. In these cases, you fall into the Stage 1 category of hypertension if your readings are between 140 to 159 systolic or 90 to 99 diastolic.

You fall into the Stage 2 hypertension category if your readings are at or greater than 160 systolic or 100 or greater diastolic. When systolic and diastolic pressures fall into different categories, your health care professional should select the higher category to classify your blood pressure. For example, 160/80 mmHg would be considered stage 2 hypertension.

If you are hypertensive and have begun receiving initial medication therapy, you will probably need to return for follow-up and adjustment of medications once a month until your blood pressure goal is reached. More frequent visits may be necessary for those with Stage 2 hypertension.

Some people experience so-called "white coat hypertension," which is elevated blood pressure caused by the anxiety and stress that they feel when they visit their health care professional. At home, you can check your blood pressure in a setting that's more comfortable for you to get a more accurate reading.

Home blood pressure monitoring also gives you the opportunity to measure your own blood pressure when your health care professional's office is not open. Inexpensive devices for home blood pressure monitoring are available at most pharmacies. Be sure to have your health care professional check your home blood pressure device when you start using it to make sure it's providing accurate readings.

Also, don't make any changes in your, medication based on home blood pressure readings without first consulting your health care professional. Home blood pressure monitoring is an excellent adjunct to monitoring by your health care professional, but should not be done in lieu of professional monitoring.

For many older Americans, only the systolic blood pressure is high, a condition known as "isolated systolic hypertension," or ISH (systolic at or above 140 mm/Hg and diastolic under 90 mm/Hg). Research finds that diastolic blood pressure rises until about age 55 and then declines, while systolic blood pressure increases steadily with age.

About 65 percent of all people with hypertension age 60 and older have ISH; the same group that has the poorest hypertension control rate. For example, in individuals age 70 and older with hypertension, only 25 percent of African Americans and only 18 percent of Caucasians have their blood pressure under control to below 140/90 mm Hg.

NHLBI and the National High Blood Pressure Education Program (NHBPEP) emphasize systolic blood pressure for both the diagnosis and treatment of hypertension in middle-aged and older adults; it is a better blood pressure indicator than diastolic when determining your risk of heart disease and stroke.

The poor control of ISH is primarily the result of inadequate systolic blood pressure control, notes the NHLBI and the NHBPEP.

Findings from NHLBI's long-term Framingham Heart Study, which involved nearly 5,000 people, showed that systolic blood pressure alone correctly identified 91 percent of those who may need antihypertensive therapy, while diastolic blood pressure alone correctly identified only 22 percent of them. Among those over age 60, systolic blood pressure alone was even better than diastolic pressure alone in correctly classifying high blood pressure.

In addition to taking blood pressure readings from both arms, your health care professional may also conduct the following during a hypertension exam:

• A complete medical history. Make sure you tell your doctor about any alternative medicines you're taking such as herbs, over-the-counter drugs and supplements. The American Heart Association notes that some may be life-threatening when combined with medicines to treat high blood pressure.

• A physical examination. This includes checking your retinas and abdomen, listening to your lungs and heart, taking your pulse in several areas, including your feet, looking for swelling in your ankles.

• A urinalysis. The urine is tested for elevated protein, sugar, white blood cells or other abnormalities.

• An electrocardiogram. Your health care professional will position a number of small contacts on your arms, legs and chest to connect them to an ECG machine. The results will be analyzed for any abnormalities indicating an enlarged heart or other abnormality.

• A kidney profile. The blood is tested for abnormalities such as elevated creatinine.

• A thyroid profile. The blood is tested for abnormalities such as an elevated level of thyroid hormone, and the thyroid gland is physically felt for enlargement.

Risk Factors for Hypertension

Although there are several risk factors for hypertension, family history is the primary one. If you have two immediate family members who developed high blood pressure before age 60, you have two times the risk, and your risk increases with each additional immediate family member who has high blood pressure.

African Americans and Hispanic Americans are more likely to develop high blood pressure than Caucasians. Studies find that having "Type A" qualities -- being very driven, a perfectionist who doesn't cope well with stress, know how to relax and is quick-tempered, increases the risk of hypertension in men and may also increase the risk for women.

Other risk factors for hypertension include:

• Increasing age

• Salt sensitivity

• Obesity

• Heavy alcohol consumption, defined as more than two drinks a day for men and more than one drink a day for women.

• Use of oral contraceptives

• An inactive lifestyle

• Regular smoking or use of smokeless-tobacco, like snuff or chewing tobacco

• High uric acid levels (anything over 7 mg/ml of blood)

Unfortunately, there is no proven method of preventing preeclampsia or pregnancy-induced hypertension and no tests to diagnose or predict these conditions. The only way to insure a safe pregnancy is with regular visits to your health care professional for checks of the level of protein in your urine and your blood pressure.

You should also should do everything you can on your own to prevent pregnancy-induced high blood pressure, including regular physical activity and limiting salt intake.