What Is High Blood Pressure?

High blood pressure (HBP) is a serious condition that can lead to coronary heart disease, heart failure, stroke, kidney failure, and other health problems.

"Blood pressure" is the force of blood pushing against the walls of the arteries as the heart pumps out blood. If this pressure rises and stays high over time, it can damage the body in many ways.


Overview

About 1 in 3 adults in the United States has HBP. HBP itself usually has no symptoms. You can have it for years without knowing it. During this time, though, it can damage the heart, blood vessels, kidneys, and other parts of your body.

This is why knowing your blood pressure numbers is important, even when you're feeling fine. If your blood pressure is normal, you can work with your health care team to keep it that way. If your blood pressure is too high, you need treatment to prevent damage to your body's organs.


Blood Pressure Numbers

Blood pressure numbers include systolic (sis-TOL-ik) and diastolic (di-a-STOL-ik) pressures. Systolic blood pressure is the pressure when the heart beats while pumping blood. Diastolic blood pressure is the pressure when the heart is at rest between beats.

You will most often see blood pressure numbers written with the systolic number above or before the diastolic, such as 120/80 mmHg. (The mmHg is millimeters of mercury—the units used to measure blood pressure.)

The table below shows normal numbers for adults. It also shows which numbers put you at greater risk for health problems. Blood pressure tends to go up and down, even in people who have normal blood pressure. If your numbers stay above normal most of the time, you're at risk.

Category Systolic   Diastolic
Normal Less than 120 And Less than 80
Prehypertension 120–139 Or 80–89
Stage 1 140–159 Or 90–99
Stage 2 160 or higher Or 100 or higher

The ranges in the table apply to most adults (aged 18 and older) who don't have short-term serious illnesses.

All levels above 120/80 mmHg raise your risk, and the risk grows as blood pressure levels rise. "Prehypertension" means you're likely to end up with HBP, unless you take steps to prevent it.

If you're being treated for HBP and have repeat readings in the normal range, your blood pressure is under control. However, you still have the condition. You should see your doctor and stay on treatment to keep you blood pressure under control.

Your systolic and diastolic numbers may not be in the same blood pressure category. In this case, the more severe category is the one you're in. For example, if your systolic number is 160 and your diastolic number is 80, you have stage 2 HBP. If your systolic number is 120 and your diastolic number is 95, you have stage 1 HBP.

If you have diabetes or chronic kidney disease, HBP is defined as 130/80 mmHg or higher. HBP numbers also differ for children and teens. (For more information, see "How Is High Blood Pressure Diagnosed?")


What Causes High Blood Pressure?

Blood pressure tends to rise with age, unless you take steps to prevent or control it.

Certain medical problems, such as chronic kidney disease, thyroid disease, and sleep apnea, may cause blood pressure to rise. Certain medicines, such as asthma medicines (for example, corticosteroids) and cold-relief products, also may raise blood pressure.

In some women, blood pressure can go up if they use birth control pills, become pregnant, or take hormone therapy.

Women taking birth control pills usually have a small rise in both systolic and diastolic blood pressures. If you already have high blood pressure (HBP) and want to use birth control pills, make sure your doctor knows about your HBP. Talk to him or her about how often you should have your blood pressure checked and how to control it while taking the pill.

Taking hormones to reduce the symptoms of menopause can cause a small rise in systolic blood pressure. If you already have HBP and want to start using hormones, talk to your doctor about the risks and benefits. If you decide to take hormones, find out how to control your blood pressure and how often you should have it checked.

Children younger than 10 years who have HBP often have another condition that's causing it (such as kidney disease). Treating the underlying condition may resolve the HBP.

The older a child is when HBP is diagnosed, the more likely he or she is to have essential hypertension. This means that doctors don't know what's causing the HBP.


What Is Hypotension?

Hypotension (HI-po-TEN-shun) is abnormally low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood.

Blood pressure is measured as systolic (sis-TOL-ik) and diastolic (di-a-STOL-ik) pressures. "Systolic" refers to blood pressure when the heart beats while pumping blood. "Diastolic" refers to blood pressure when the heart is at rest between beats.

You most often will see blood pressure numbers written with the systolic number above or before the diastolic number, such as 120/80 mmHg. (The mmHg is millimeters of mercury—the units used to measure blood pressure.)

Normal blood pressure in adults is lower than 120/80 mmHg. Hypotension is blood pressure that's lower than 90/60 mmHg.


Overview

Blood pressure doesn't stay the same all the time. It lowers as you sleep and rises when you wake up. Blood pressure also rises when you're excited, nervous, or active.

Your body is very sensitive to changes in blood pressure. For example, if you stand up quickly, your blood pressure may drop for a short time. Your body adjusts your blood pressure to make sure enough blood and oxygen are flowing to your brain, kidneys, and other vital organs.

Most forms of hypotension happen because your body can't bring blood pressure back to normal or can't do it fast enough.

Some people have low blood pressure all the time. They have no signs or symptoms, and their low blood pressure is normal for them.

In other people, certain conditions or factors cause abnormally low blood pressure. As a result, less blood and oxygen flow to the body's organs.

For the most part, hypotension is a medical concern only if it causes signs or symptoms or is linked to a serious condition, such as heart disease. Signs and symptoms of hypotension may include dizziness, fainting, cold and sweaty skin, fatigue (tiredness), blurred vision, or nausea (feeling sick to your stomach).

In extreme cases, hypotension can lead to shock.

content provided by National Heart and Lung Institute

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