Hypertension, or high blood pressure, is a condition in which blood pumped by the heart through the arteries pushes against the artery walls with greater than normal force. This extra force can damage and weaken arteries and strain the heart, thereby increasing the risk of heart disease.

What Is Hypertension?

Hypertension is the medical term for high blood pressure. High blood pressure occurs when blood pumped by the heart through the arteries pushes against the artery walls with greater than normal force. Arteries are blood vessels that carry blood from the heart to organs and tissues throughout the body. Healthcare workers measure blood pressure with a device called a sphygmomanometer (sfig-mo-muh-NAH-meh-ter). This measurement yields two numbers, such as 120/80, which is considered normal for adults. The measurement 140/90 is considered high for adults; normal values for children are lower and increase with age and body size.

It is normal for a person's blood pressure to rise during times of stress or excitement. However, when blood pressure remains high for extended periods, doctors consider it to be a serious medical condition that endangers an individual's health. The higher the pressure is and the longer it persists without treatment, the greater the risk becomes.

People with hypertension are more likely to suffer a stroke * , heart attack * , or kidney or heart failure. For this reason, and because most affected people show no symptoms until extensive damage is done, hypertension is often called the “silent killer.”

Who Has High Blood Pressure?

Public health officials estimate that approximately one in three American adults has high blood pressure. This prevalence * is similar in most industrialized Western countries. Although many people believe hypertension is rare in developing countries, several 2015 studies found that it is increasingly common in these countries as well.

Approximately 20 percent of the American adults with hypertension are unaware of their condition. Many such individuals first become aware they are affected during a routine healthcare checkup.

Overall, the prevalence of hypertension in the United States is similar in men and women, although men under age 45 are more likely to develop it than women under 45 are. Women over age 65 are affected more often than men over 65. The disease is also more common and tends to develop earlier in blacks than in Caucasians and non–African American Hispanics. More black women than men are affected.

Hypertension is fairly uncommon in children and teenagers and becomes more prevalent as people age. Experts estimate that between 2 and 5 percent of children and adolescents have high blood pressure.

The disease is also most likely to affect individuals who smoke, drink excessive amounts of alcohol, eat a diet high in sodium (salt), are obese, and have a family history of high blood pressure.

How Does the Body Control Blood Pressure?

The cardiovascular * , nervous, renal * , and endocrine * systems all contribute to controlling blood pressure to ensure that it stays high enough for blood to reach all the body organs. Short-term control depends on regulating how much blood the heart pumps, how forcefully it pumps, and the amount of resistance to blood flow in the blood vessels. If blood pressure decreases too much, sensors in artery walls send signals to the brain, heart, kidneys, arterioles * , and veins to raise this pressure. The brain produces chemicals that signal the heart to beat faster and more forcefully. The veins narrow to send more blood to the heart and arterioles narrow to increase resistance to blood flow. The kidneys produce the hormone * renin, which is converted to angiotensin II, which further tightens blood vessels. This all happens within seconds.

Longer-term regulation (over hours and days) depends on the kidneys adjusting the amount of urine they produce. When the kidneys absorb salt and fluid from urine and send less urine out of the body, this increases the amount of fluid in the blood vessels and raises blood pressure.

Blood pressure normally rises and falls according to an individual's activities. The need for increased blood pressure arises when an individual is active and muscles need more blood flow to deliver more oxygen. Once the person is at rest, the blood pressure returns to normal.

What Causes Hypertension?

Hypertension results from genetic or behavioral factors or from other diseases that change the body's normal blood pressure control mechanisms. These factors can affect the way the kidneys control the body's fluid balance, the amount of renin or other regulatory chemicals, or the structure of blood vessels.

Mutations * in genes that control kidney function and hormone production cause 2 to 3 percent of cases of hypertension. Five to ten percent of cases result from other diseases, such as chronic (long-term) kidney disease, sleep apnea * , certain tumors, diabetes, or thyroid problems.

The precise cause of most hypertension cases is unknown. Doctors call this essential, or primary, hypertension. Cases that result from another disease are termed secondary hypertension.

Although the precise cause of an individual's hypertension may be unknown, medical experts do know that obesity, lack of physical activity, smoking, excessive alcohol intake, and excessive salt intake all contribute. Taking certain medications for asthma, colds, or birth control can also lead to high blood pressure by affecting factors that influence blood vessel width, heart function, or kidney function.

How Does Hypertension Affect the Body?

Did You Know?
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The gradual damage hypertension does is also dangerous because it makes the heart work harder to pump blood. This strains the heart and contributes to hardening of the arteries. This is often accompanied by a buildup of cholesterol or other blood fats in the arteries that can block blood flow. If blockages occur in arteries connected to the heart, a heart attack can result. Blockages that affect the brain can lead to a stroke. Blockages in arterioles can lead to blindness or kidney failure.

Long-term hypertension may strain the heart so much that heart failure results.

Hypertension during pregnancy

A serious condition called pre-eclampsia (pree-ih-KLAMP-see-uh) develops in 5 to 8 percent of pregnant women, most often during the second half of pregnancy. This disorder is characterized by a sudden rise in blood pressure and may include severe headaches and malfunctioning kidneys. The risk for preeclampsia is highest in women who are pregnant for the first time, are under age 20 or over age 35, are carrying multiple fetuses, or have chronic hypertension, diabetes, migraine headaches, or lupus. If left untreated, preeclampsia can lead to eclampsia, which is characterized by seizures and extremely high blood pressure that may be fatal to the mother or baby.

How Is Hypertension Defined by Numbers?

Blood pressure is expressed as two numbers: the systolic (sis-TOL-ik) pressure and the diastolic (DYE-uh-STOL-ik) pressure. The first (higher) number is the systolic pressure, which indicates the pressure against the artery walls during systole (SIS-tuh-lee), when the heart contracts. The second (lower) number is the diastolic pressure, which occurs during diastole (DY-as-tuh-lee), when the heart relaxes between beats.

These numbers are read from a gauge on a sphygmomanometer. When written, the two numbers are separated by a slash. Doctors consider readings of 120/80 or lower to be normal in adults. Many healthy young adults in their 20s and 30s have blood pressure readings under 120/80, and readings in healthy children are even lower. This is why doctors diagnose hypertension in children using percentile comparisons. A child of a particular age and height is diagnosed with high blood pressure if his or her average readings are higher than those of 95 percent of children of the same age and height.

Adults with systolic pressure readings between 120 and 139 or diastolic readings between 80 and 89 are considered to have prehypertension and are advised to check their pressure regularly. Those with systolic readings between 140 and 159 or diastolic readings between 90 and 99 have stage 1, or moderate, hypertension. Those with a systolic pressure of 160 or higher or a diastolic pressure above 110 are diagnosed with stage 2, or severe, hypertension. Anyone with a systolic pressure of 180 or higher or a diastolic reading above 110 is advised to seek emergency treatment for a hypertensive crisis.


A sphygmomanometer is the instrument used to measure blood pressure. It consists of an inflatable cuff that is wrapped around the upper arm, a rubber bulb to inflate the cuff, and a gauge that gives the pressure reading in millimeters of mercury (mmHg).

The pressure is read on a gauge, which can be a glass column filled with mercury (the earliest type), a dial, or a digital readout. In some instruments, the blood pressure may be read directly, without the use of a stethoscope. The actual numbers in blood pressure readings represent mmHg, based on the original glass column filled with mercury.

First, the cuff is inflated until it fits tightly enough to briefly stop blood flow through the brachial artery in the arm. Then, the technician slowly releases the pressure on the arm using a valve that lets air out of the cuff, while listening through a stethoscope (STETH-uh-skope) placed just below the cuff. The sound that is heard when blood starts flowing again represents the systolic pressure, which comes from the heart contracting to pump blood. When the sound of blood rushing through the artery stops, this represents the diastolic pressure that results from the heart muscle relaxing between beats.

The gauge indicates the pressure reading at each of these points. The original type of gauge was a glass column partially filled with mercury, which rises and falls as the cuff is inflated or deflated. This is why blood pressure readings are expressed in millimeters of mercury. Other types of gauges in the form of a dial or a digital readout are available. Some do not require the use of a stethoscope.

How Is Hypertension Diagnosed?

When assessing or diagnosing hypertension, a physician takes more than one reading, especially if the first reading is high. This is because blood pressure changes frequently. Moreover, some people have what is called “white coat hypertension,” meaning that their blood pressure tends to go up when they experience stress while visiting a doctor. To get an accurate reading, doctors attempt to reassure patients that having blood pressure measured is painless. They also allow patients to relax for a while before taking another reading.

What the Numbers Mean

Blood pressure is measured in units called millimeters of mercury (mmHg). Measurements are written as two numbers, one over the other. The number on top is the systolic pressure, or the force with which blood hits the artery walls when the heart contracts. The bottom number is the diastolic pressure against the artery walls when the heart relaxes between beats. When systolic and diastolic blood pressures fall into different diagnostic categories, the diagnosis is based on the more severe category.

In general, doctors consider blood pressure that is lower than the recommended levels to be a good thing, since it lowers the risk of heart disease. Most physicians believe that blood pressure is dangerously low only if it causes noticeable symptoms, including dizziness, fainting, blurred vision, extreme fatigue, an inability to concentrate, cold clammy skin, or rapid, shallow breathing.

A sudden and extreme drop in blood pressure can also be dangerous or even life threatening because it can lead to shock. This can occur due to excessive bleeding, dehydration, or a severe infection or allergic reaction.

Blood Pressure Categories and Measurement

Blood Pressure Categories and Measurement
Illustration by Electronic Illustrators Group. © 2016 Cengage Learning®.

Factors Contributing to High Blood Pressure (Hypertension)

Factors Contributing to High Blood Pressure (Hypertension)
Table by Electronic Illustrators Group. © 2016 Cengage Learning®.

Although blood pressure tends to increase with age, experts emphasize that readings above the recommended ideal levels represent a health risk for people of any age and should not be ignored.

How Is Hypertension Treated?

Doctors treat people whose high blood pressure is caused by another disease or a medication by treating the other disorder or changing the responsible medicine. The firstline treatment for people with essential hypertension is lifestyle modifications. If this does not lower blood pressure enough, blood pressure–reducing medications may be prescribed.

Good health habits

Many people with prehypertension or mild hypertension can lower their blood pressure sufficiently with lifestyle modifications that may include losing weight, exercising regularly, eating a low-salt, low-fat diet that is heart healthy, limiting alcohol intake, avoiding tobacco smoke, and coping effectively with stress.

Studies indicate that losing weight gradually through regular exercise and by eating a healthful diet that is high in fruits, vegetables, and whole grains and low in fats, sodium, and processed foods is the most effective strategy for helping to control hypertension.

Antihypertensive Drugs

Antihypertensive Drugs

Medical experts believe that most Americans, even those who do not have high blood pressure, ingest far too much salt. Most people, especially those who do not add salt to their food, are surprised to learn how much salt is in processed, packaged, and restaurant foods. In fact, only 5 to 10 percent of most Americans' salt intake comes from salt they add to their food. Bread, deli meats, cheese, canned or packaged soups, frozen dinners, and pizza are among the foods that contain huge amounts of sodium. Doctors recommend that people read packaged food labels to determine sodium content and that most people should restrict their daily salt intake to 2,300 milligrams (one teaspoon) or less. Those with hypertension should eat far less sodium than this. Eating fewer packaged foods and more fresh fruits, vegetables, legumes, unsalted nuts and other snack foods, and more whole g rains is an effective way of reducing sodium intake.

Many people are also unaware of how much influence life's ongoing stressors have on blood pressure. Doctors advise people to deal with stress in their lives by practicing relaxation techniques and engaging in regular exercise to help lower blood pressure.

Unhealthy ways in which some individuals cope with stress, including smoking, drinking, and taking street drugs, also contribute to hypertension and other medical problems. For instance, nicotine in cigarettes raises the heart rate and constricts blood vessels, and drugs like cocaine and methamphetamine are highly damaging to blood pressure and the cardiovascular system. These substances are unhealthy for anyone, but those with hypertension should be extra-careful to avoid them.


When lifestyle modifications do not lower blood pressure sufficiently, doctors may prescribe any of a variety of blood pressure-reducing medications. The specific drugs prescribed depend on individual patients needs.

One type of commonly prescribed blood pressure–reducing drugs are diuretics, which lower blood pressure by increasing the amount of urine production to flush out excessive amounts of fluids and salt. Another type, angiotensin converting enzyme (ACE) inhibitors, relax blood vessels and decrease the heart rate and the force with which the heart pumps by preventing the production of angiotensin II. Beta-blockers, another commonly prescribed group of drugs, decrease the heart rate and output force by blocking the action of the chemicals norepinephrine and epinephrine. Other types of medications lower blood pressure through different mechanisms of action.

Prescription drugs for hypertension may have various side effects, depending upon the drug and the person taking it. All antihypertensive drugs may cause dizziness and fainting if the blood pressure is lowered too much.

Doctors advise patients to use a blood-pressure measuring device available for home use to keep tabs on their readings. Doctors stress that patients should contact the physician immediately if levels fall too low or grow too high, or if serious side effects of medications occur.

Can Hypertension Be Prevented?

Many cases of hypertension can be prevented by maintaining a healthy weight, eating a heart-healthy diet, not smoking, and exercising regularly. Physicians emphasize that prevention should begin in childhood, since kids who eat a high-salt, high-fat diet and are obese and inactive are at vastly increased risk for developing hypertension during childhood or adolescence. Studies indicate that the prevalence of hypertension in children and teens has grown nearly 30 percent since 2000, mostly because more and more children are obese. Many affected kids are unaware of their condition, while the damage it does may be silently accumulating.

Since early diagnosis and treatment can prevent harmful complications, doctors recommend that most children have yearly blood pressure readings starting at age three. Those with risk factors such as a family history of hypertension are advised to be routinely checked earlier.

See also Diabetes • Heart Disease: Overview • Hypotension • Obesity • Preeclampsia/Eclampsia • Stroke


Books and Articles

Manger, William M., and Norman M. Kaplan. 101 Questions and Answers about Hypertension. 2nd ed. Nashville, TN: Hunter House, 2011.

Mayo Clinic. High Blood Pressure. New York: Rosetta Books, 2015.


Centers for Disease Control and Prevention. “High Blood Pressure.” CDC.gov . http://www.cdc.gov/bloodpressure/index.htm (accessed April 20, 2016).

MedlinePlus. “High Blood Pressure.” U.S. National Library of Medicine. https://www.nlm.nih.gov/medlineplus/highbloodpressure (accessed June 14, 2016).


American College of Cardiology. 2400 N St. NW, Washington, DC 20037. Toll-free: 800-253-4636. Website: http://www.acc.org (accessed April 20, 2016).

American Society of Hypertension. 244 Madison Ave., Suite 136, New York, NY 10016. Telephone: 212-696-9099. Website: http://www.ash-us.org (accessed April 20, 2016).

Mayo Clinic. 200 First St. SW, Rochester, MN 55905. Telephone: 507-284-2511. Website: http://www.mayoclinic.org (accessed April 20, 2016).

National Heart, Lung, and Blood Institute. PO Box 30105, Bethesda, MD 20824-0105. Telephone: 301-592-8573. Website: http://www.nhlbi.nih.gov/ (accessed April 20, 2016).

* stroke is an event in which blood flow to the brain is reduced or blocked. A stroke may occur when a blood vessel supplying the brain becomes clogged or bursts, depriving brain cells of oxygen. As a result, nerve cells in the affected area of the brain, and the specific body parts they control, may not properly function.

* heart attack is a general term that refers to a sudden, intense episode of heart injury. It is usually caused by blockage of a coronary artery, which stops blood flow to the heart and prevents blood from supplying the heart muscle with oxygen.

* prevalence of a disease or condition refers to how common it is in a given population.

* cardiovascular (car-dee-oh-VAScue- lar) system refers to the heart and blood vessels.

* renal (REE-nal) refers to the kidneys.

* endocrine (EN-duh-krin) system is a group of glands in the body that produce hormones that regulate growth, metabolism (the ways in which food is processed and used), sleep, mood, reproduction, cell function, and other processes.

* arterioles (ar-TEER-ee-oles) are small arteries.

* hormones are chemical messengers produced by glands that release these substances into the bloodstream. Hormones regulate many body processes, including growth, development, metabolism, reproduction, and mood.

* mutations (mew-TAY-shuns) are changes in genes or the chromosomes (KRO-muh-somz) on which they reside.

* sleep apnea is a disorder in which an individual's throat narrows and blocks the airways many times during sleep, causing the person to wake up many times gasping for air.

* seizures (SEE-zhurs) are changes in brain function and behavior that result from sudden, abnormal electrical activity in the brain. Seizures often involve uncontrollable shaking of the body and may or may not involve a loss of consciousness.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)