Blood pressure is the pressure of the blood against the walls of the arteries.

Blood pressure results from two forces. One is created by the heart as it pumps blood into the arteries and through the circulatory system. The other is the force of the arteries as they resist the blood flow.

What do blood pressure numbers indicate?

• The higher (systolic) (sis-TOL'ik) number represents the pressure while the heart contracts to pump blood to the body.
• The lower (diastolic) (di"as-TOL'ik) number represents the pressure when the heart relaxes between beats.

The systolic pressure is always stated first and the diastolic pressure second. For example: 118/76 (118 over 76); systolic = 118, diastolic = 76.

Blood pressure below 120 over 80 mmHg (millimeters of mercury) is considered best for adults. A systolic pressure of 120 to 139 mmHg or a diastolic pressure of 80 to 89 mmHg is considered "prehypertension" and needs to be watched carefully. A blood pressure reading of 140 over 90 or higher is considered elevated or high.

How can I tell if I have high blood pressure?

High blood pressure usually has no symptoms. In fact, many people have high blood pressure for years without knowing it. That's why it's called the "silent killer." Hypertension (hi"per-TEN'shun) is the medical term for high blood pressure. It doesn't refer to being tense, nervous or hyperactive. You can be a calm, relaxed person and still have high blood pressure.

A single elevated blood pressure reading doesn't mean you have high blood pressure, but it's a sign that further observation is required. Ask your doctor how often to check it or have it checked. Certain diseases, such as kidney disease, can cause high blood pressure. In 90 to 95 percent of cases, the cause of high blood pressure is unknown.

The only way to find out if you have high blood pressure is to have your blood pressure checked. Your doctor or other qualified health professional should check your blood pressure at least once every two years, or more often if necessary.

Resources:
National Heart, Lung, and Blood Institute