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Nearly 1 in 3 American adults has high blood pressure (hypertension). Once high blood pressure develops, it usually lasts a lifetime. The good news is that it can be treated and controlled.
Each time your heart beats, it pumps blood through the blood vessels, or arteries, that run through your body. Blood pressure is the force of the blood pushing against the walls of 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 (measured in millimeters of mercury, a unit for measuring pressure). 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 mmHg. When the level stays high, 140/90 mmHg 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 mmHg is considered normal. In general, lower is better. However, blood pressure lower than 90/60 mmHg can be a cause for concern and should be checked out by a doctor.
Doctors classify blood pressures under 140/90 mmHg as either normal or prehypertension. If your blood pressure is in the prehypertension range, it is more likely that you will end up with high blood pressure unless you take action to prevent it.
When systolic and diastolic blood pressures fall into different categories, the higher category should be used to classify blood pressure level. For example, 160/80 mmHg would be stage 2 high blood pressure.
There is an exception to the above definition of high blood pressure. A blood pressure of 130/80 mmHg or higher is considered high blood pressure in people with diabetes and chronic kidney disease.
About two out of every three people over the age of 60 who have high blood pressure have isolated systolic hypertension. This means that only the top number, the systolic pressure, is high (140 mmHg or higher). Isolated systolic hypertension can be as harmful as when both numbers are high.