Nearly one in three American adults has high blood pressure. Once high blood pressure develops, it usually lasts a lifetime. The good news is that it can be treated and controlled.

High blood pressure is called "the silent killer" because it usually has no symptoms. Some people may not find out they have it until they have trouble with their heart, brain, or kidneys.

Blood is carried from the heart to all parts of your body in vessels called arteries. Blood pressure is the force of the blood pushing against the walls of the arteries. Each time the heart beats (about 60-70 times a minute at rest), it pumps out blood into the arteries. Your blood pressure is at its highest when the heart beats, pumping the blood. This is called systolic pressure. When the heart is at rest, between beats, your blood pressure falls. This is the diastolic pressure.

Blood pressure is always given as these two numbers, the systolic and diastolic pressures. Both are important. Usually they are written one above or before the other, such as 120/80 mmHg. The top number is the systolic and the bottom the diastolic. When the two measurements are written down, the systolic pressure is the first or top number, and the diastolic pressure is the second or bottom number (for example, 120/80). If your blood pressure is 120/80, you say that it is "120 over 80."

Blood pressure changes during the day. It is lowest as you sleep and rises when you get up. It also can rise when you are excited, nervous, or active.

Still, for most of your waking hours, your blood pressure stays pretty much the same when you are sitting or standing still. That level should be lower than 120/80. When the level stays high, 140/90 or higher, you have high blood pressure. With high blood pressure, the heart works harder, your arteries take a beating, and your chances of a stroke, heart attack, and kidney problems are greater.

A blood pressure reading below 120/80 is considered normal. In general, lower is better. However, very low blood pressures can sometimes be a cause for concern and should be checked out by a doctor.

A blood pressure of 140/90 or higher is considered high blood pressure. Both numbers are important. If one or both numbers are usually high, you have high blood pressure. If you are being treated for high blood pressure, you still have high blood pressure even if you have repeated readings in the normal range.

It is important to take steps to keep your blood pressure under control. The treatment goal is blood pressure below 140/90 and lower for people with other conditions, such as diabetes and kidney disease. Adopting healthy lifestyle habits is an effective first step in both preventing and controlling high blood pressure. If lifestyle changes alone are not effective in keeping your pressure controlled, it may be necessary to add blood pressure medications. In this section you will learn about blood pressure-lowering lifestyle habits and blood pressure medications.

Types of Blood Pressure Medications

Diuretics are sometimes called "water pills" because they work in the kidney and flush excess water and sodium from the body.

Beta-blockers reduce nerve impulses to the heart and blood vessels. This makes the heart beat slower and with less force. Blood pressure drops and the heart works less hard.

Angiotensin converting enzyme (ACE) inhibitors prevent the formation of a hormone called angiotensin II, which normally causes blood vessels to narrow. The ACE inhibitors cause the vessels to relax and blood pressure goes down.

Alpha-blockers reduce nerve impulses to blood vessels, which allows blood to pass more easily, causing the blood pressure to go down.

Alpha-beta-blockers work the same way as alpha-blockers but also slow the heartbeat, as beta-blockers do. As a result, less blood is pumped through the vessels and the blood pressure goes down.

Nervous system inhibitors relax blood vessels by controlling nerve impulses. This causes the blood vessels to become wider and the blood pressure to go down.

Vasodilators directly open blood vessels by relaxing the muscle in the vessel walls, causing the blood pressure to go down.