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What Is High Blood Pressure?
High blood pressure is a blood pressure reading of
140/90 mmHg or higher. Both numbers are important.
Nearly 1 in 3 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. When high blood
pressure is not found and treated, it can cause:
- The heart to get larger, which may lead to heart
failure.
- Small bulges (aneurysms (AN-u-risms)) to form in
blood vessels. Common locations are the main artery from the heart (aorta);
arteries in the brain, legs, and intestines; and the artery leading to the
spleen.
- Blood vessels in the kidney to narrow, which may
cause kidney failure.
- Arteries throughout the body to "harden" faster,
especially those in the heart, brain, kidneys, and legs. This can cause a heart
attack, stroke, kidney failure, or amputation of part of the leg.
- Blood vessels in the eyes to burst or bleed,
which may cause vision changes and can result in blindness.
What Is Blood Pressure?
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 (sis-TOL-ik) pressure. When the heart is at rest, between
beats, your blood pressure falls. This is the diastolic (di-a-STOL-ik)
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.
What Is Normal Blood Pressure?
A blood pressure reading below 120/80 mmHg is
considered normal. In general, lower is better. However, very low blood
pressure can sometimes 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.
- Normal blood pressure is lower than 120/80
mmHg.
- Prehypertension is blood pressure between 120 and
139 for the top number, or between 80 and 89 for the bottom number. For
example, blood pressure readings of 138/82, 128/89, or 130/86 are all in the
prehypertension range. 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.
What Is High Blood Pressure?
A blood pressure of 140/90 mmHg 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 and
have repeated readings in the normal range, you still have high blood
pressure.
There are two levels of high blood pressure: stage 1
and stage 2 (see the chart below).
Categories for Blood Pressure Levels in
Adults (in mmHg, millimeters of
mercury)a
| Category |
Systolic
(top number) |
Diastolic
(bottom number) |
| Normal |
Less than 120 |
Less than 80 |
| Prehypertension |
120–139 |
80–89 |
| High blood
pressure |
|
|
| Stage 1 |
140–159 |
90–99 |
| Stage 2 |
160 or higher |
100 or higher |
| a |
For adults 18 and
older who are not on medicine for high blood pressure; are not having a
short-term serious illness; and do not have other conditions, such as diabetes
and kidney disease. |
| Note:
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.
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