Also Known As
High Blood Pressure
HBP
This article was last reviewed on
This article waslast modified on
February 28, 2018.
What is hypertension?

Hypertension, also known as high blood pressure, is a persistent elevation in blood pressure that puts additional strain on the heart. Over time, it can cause serious damage to the heart as well as other organs, such as the kidneys, brain, and eyes. About 46% of U.S. adults have high blood pressure.

Blood pressure (BP) is the force that blood exerts on the walls of the arteries. It depends on the strength and rate of the heart's contraction as it pumps blood and on the resistance to the flow of blood through the arteries. The amount of resistance depends on the elasticity and diameter of the blood vessels and the volume of blood flowing through them. The narrower the arteries and the more blood pumping through them, the higher the blood pressure will be. Maintaining a healthy lifestyle can help delay or prevent hypertension.

Blood pressure rises and falls during the day depending on a person's level of activity and physical and emotional stress. Largely controlled by the autonomic nervous system (the part of the nervous system that controls involuntary actions), BP is also affected by several different hormones, including angiotensin II, aldosterone and catecholamines.

Measuring BP takes into account two pressures, measured in millimeters of mercury (mm Hg). The first, systolic pressure, is the force exerted on the blood vessel walls when the heart is pumping blood. Diastolic pressure reflects the force present when the heart relaxes between beats. They are written as systolic over diastolic pressure. For instance, a blood pressure of 120/80 mm Hg or 120 over 80 corresponds to a systolic pressure of 120 and a diastolic pressure of 80.

A single measurement of blood pressure is not diagnostic. Typically, multiple readings are taken on different days and, if measurements are consistently high, a diagnosis of high blood pressure is made.

Usually, diastolic pressures will mirror systolic pressures, but as people age, the diastolic pressure tends to level out. Then, the form of hypertension that involves primarily the systolic pressure (called isolated systolic hypertension) becomes more common. In general, the greater the blood pressure for extended periods of time, the greater the potential for damage.

The classifications of blood pressure based on 2017 guidelines developed by the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines are summarized in the table below.

Blood Pressure Classifications

Category Systolic mm Hg (top number-force when heart is pumping)   Diastolic mm Hg (bottom number-force when heart is at rest)
Normal Less than 120 and Less than 80
Elevated 120-129 and Less than 80
Hypertension Stage I 130-139 or 80-89
Hypertension Stage II Equal to or greater than 140 or Equal to or greater than 90

These categories apply to most adults with no known illness at the time of testing and are based on an average of 2 or more blood pressure readings obtained on 2 or more occasions.

Though the above guidelines are important, they are not the only hypertension guidelines and currently there is no consensus on them. In 2014, experts appointed to the Eighth Joint National Committee (JNC 8) proposed a different set of guidelines and blood pressure goals and some physician groups continue to endorse these recommendations. The table below summarizes the new goals or target blood pressure readings for specific populations:

Blood Pressure Goals

Category Systolic and Diastolic blood pressure (mm Hg)
General population (older than or equal to 60 years old) Less than 150/90
General population (younger than 60 years old) Less than 140/90
Diabetic Less than 140/90
Non-diabetic chronic kidney disease Less than 140/90

Given the significant differences in guidelines, it is important to talk to your healthcare practitioner about the blood pressure goals and treatments or lifestyle changes that best fit your individual situation.

Accordion Title
About Hypertension
  • Signs and Symptoms

    In most people, high blood pressure rarely causes any signs or symptoms.  It's possible to have it for many years without realizing it. Often, it only becomes apparent during a routine health checkup. Rarely, even when levels are life-threatening, high blood pressure may cause only a few symptoms, such as headaches, dizziness, or frequent nosebleeds.

    For this reason, hypertension is known as the "silent killer," quietly increasing the risk of developing stroke, heart disease, heart attack, kidney damage, and blindness. The greater the blood pressure for extended periods, the greater the potential for damage. That is why it is important for people to have their blood pressure checked on a regular basis.

  • Causes

    In most cases, the cause of hypertension is unknown, or idiopathic. This form of high blood pressure is called essential or primary hypertension and is the most common type in American adults.

    According to the Centers for Disease Control and Prevention, more than 50% of people age 50 and older have high blood pressure. Women are about as likely as men to develop high blood pressure, though this varies somewhat by age. For people younger than age 45, more men than women are affected, while for those age 65 and older, more women than men are affected. Americans of African descent develop high blood pressure more often and at an earlier age than those of European and Hispanic descent.

    Although it may not be possible to identify the cause of hypertension, several factors are known to increase the risk and worsen high blood pressure. These include:

    • Obesity
    • Sedentary lifestyle - not getting enough exercise
    • Smoking cigarettes or using other tobacco products
    • Drinking excessive amounts of alcohol
    • Excessive dietary sodium
    • Use of oral contraceptives or hormone therapy
    • Use of drugs such as steroids, cocaine, and amphetamines
    • Aging
    • Family history


    Hypertension that is due to one or more identifiable underlying conditions or use of drugs is called secondary hypertension and accounts for 5% of those who have high blood pressure. It is important to identify the underlying conditions since their treatment may result in a person's blood pressure returning to normal or near normal levels.

    Examples of conditions that result in secondary hypertension include:

    • Kidney disease or damage – decreases the removal of salts and fluids from the body, increasing blood volume and pressure. Since hypertension can also cause kidney damage, this can be a progressive problem if left untreated.
    • Heart disease – this may affect the force and rate of the heart's contraction. This can also be progressive.
    • Diabetes – this condition can damage the kidneys and affect the integrity of the blood vessels over time.
    • Arteriosclerosis – a hardening of the arteries that limits their ability to dilate and constrict
    • Cushing syndrome – a disorder that involves increased production of the hormone cortisol by the adrenal gland
    • Hyperaldosteronism (Conn syndrome) – a condition characterized by an overproduction of aldosterone, a hormone that helps regulate the retention and excretion of sodium by the kidneys; it may be due to an adrenal gland tumor (usually benign).
    • Pheochromocytoma – a tumor of the adrenal gland (rare and usually benign) that produces excessive amounts of epinephrine (adrenaline); epinephrine is one of a group of hormones called catecholamines that are produced by the brain and adrenal glands in response to stress. People with a pheochromocytoma often have severe episodes of hypertension.
    • Thyroid disease – both excessive and deficient amounts of thyroid hormone production can cause increases in blood pressure.
    • Pregnancy – hypertension may develop at any time during a woman's pregnancy but is most common during the last trimester, when it can cause pre-eclampsia (toxemia), a condition characterized by increased blood pressure and retention of fluids.
  • Tests

    Tests may be done for several reasons:

    • To screen for and diagnose high blood pressure
    • To determine whether the cause is an underlying medical condition that can possibly be resolved or controlled
    • To evaluate the status of body organs, such as the kidneys, and get a baseline of organ health prior to the start of drug therapies
    • To monitor hypertension control and organ status over time


    Blood pressure measurement
    Blood pressure was traditionally measured using a stethoscope and a blood pressure cuff (called a sphygmomanometer), a device that includes a cuff, a bulb, and a pressure dial that reads the pressure in millimeters of mercury (mm Hg). This is still considered the best method but, more commonly, devices that combine a blood pressure cuff with electronic sensors are used to measure blood pressure.

    Another method is to have the individual wear a device that monitors and records the blood pressure at regular intervals during the day to evaluate blood pressure over time. This is especially helpful during the diagnostic process and can help rule out "white coat" hypertension, the high measurements that are sometimes present only when the person is in the doctor's office and not at other times. (See High Blood Pressure: Using an Ambulatory Blood Pressure Monitor on FamilyDoctor.org.)

    These forms of blood pressure measurement are considered indirect. Very rarely, a direct measurement of blood pressure may be required. This can be obtained by inserting a catheter into an artery to measure the pressure inside the blood vessel.

    Laboratory tests
    Laboratory testing is not diagnostic for hypertension, but tests are frequently ordered to detect conditions that may cause and/or make high blood pressure worse and to evaluate and monitor organ function over time.

    Examples of general tests that may be ordered include:


    Based on an individual's medical history, physical findings, and routine laboratory test results, some select, non-routine tests may be ordered to help detect, diagnose, and monitor conditions causing secondary hypertension. Examples include:

    • Aldosterone and renin – to help detect the overproduction of aldosterone by the adrenal glands (which may be due to a tumor) or renin by the kidneys (which may be due to kidney damage or narrowing of the arteries bringing blood to the kidneys)
    • Cortisol and dexamethasone suppression test – to detect an overproduction of cortisol that may be due to Cushing syndrome
    • Catecholamines and metanephrines – primarily to help detect the presence of a pheochromocytoma that can cause episodes of severe hypertension


    Non-laboratory tests
    As part of the diagnostic process and to help evaluate the status of vital organs, a health practitioner may order or perform one or more of the following:

    • ECG (electrocardiography) – to evaluate the heart rate and rhythm and look for evidence of heart damage
    • Eye exam – to look at the retina for changes in the blood vessels (retinopathy) that are caused by prolonged hypertension
    • Physical exam – to look for abdominal tenderness, listen for bruits (the sound of blood flowing through a narrowed artery), examine the thyroid gland in the throat for any enlargement or signs of dysfunction, and to detect any other clinical signs as they present
    • Imaging scans, such as X-ray or ultrasound of the kidneys or chest X-ray 
  • Prevention and Treatment

    Lifestyle changes can help lower the risk of developing hypertension. For many people with mild high blood pressure, reaching and maintaining a healthy weight, exercising regularly, limiting alcohol and salt, and stopping smoking can decrease blood pressure levels to normal and may be the only "treatment" required. Risks associated with sex (gender), race, and increasing age, however, do not disappear with lifestyle changes and, in many cases, a treatment plan that includes medications is necessary to control high blood pressure.

    There are several classes of drugs available to treat hypertension; each works differently, targeting a specific aspect of blood pressure regulation. Frequently, someone will need to take a couple of different medications together to achieve blood pressure control. Your health practitioner will work with you to select the appropriate combinations and dosages. (See How is High Blood Pressure Treated? on the NHLBI website.)

    With secondary hypertension, if the condition causing the high blood pressure can be resolved (e.g., by removing an adrenal tumor or stopping a medication) or controlled (e.g., by controlling diabetes or thyroid disease), then blood pressure levels may fall to normal or near normal levels. When a cure is not possible and control of the underlying condition consists of minimizing further damage, as may occur with kidney disease, then hypertension will be controlled with a combination of medications and the person will be monitored closely to help maintain organ function and address acute problems as they arise.

    Hypertensive urgencies, where asymptomatic blood pressure is more than 180/110 mm Hg, without organ damage, and emergencies, where organs are damaged and blood pressure measurements can be higher than 180/120 mm Hg, must be treated immediately. They may require hospitalization so that intravenous medications can be given and monitored because, if untreated, they can quickly result in organ damage.

    Pregnant women with pre-eclampsia or toxemia require rest and close monitoring by their healthcare practitioner. The only cure for pre-eclampsia is delivery of the baby. In deciding when to deliver, the healthcare practitioner will try to minimize the risk to mother and baby from pre-eclampsia while allowing the baby the maximum time to mature. The time delay must be balanced against the increasing danger of seizures and organ damage in the mother, emergency conditions that can be lethal to both the baby and the mother.

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