An Overview of High Blood Pressure

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High blood pressure (hypertension) is a condition with serious health consequences that affects some 103 million American adults. When detected and treated early, however, it can reduce the risk of heart attack, stroke, and kidney disease.

What Is Blood Pressure?

Blood pressure is the outward force that blood exerts on the walls of arteries—the blood vessels that carry blood and oxygen from the lungs to all of the organs and tissues of the body.

Arteries are composed of muscle and flexible connective tissue that stretches to accommodate the force of blood flow generated by the heart. The pumping action of the heart is what forces blood to travel through these arteries.

Blood pressure is expressed as two numbers written one on top of the other, such as 120/80, which would be verbally expressed as "One hundred twenty over eighty." Each number has a different meaning.

The top number, systolic blood pressure, reflects the force generated by the contractions of the heart. The bottom number, diastolic blood pressure, refers to the pressure of blood against the walls of the arteries when the heart is resting between contractions.

Basic Numbers to Know

After age 20, adults will have their blood pressure monitored at regular healthcare visits. This likely will be one of the first things a nurse does at the beginning of a checkup, along with taking your temperature and weighing you.

People over 40 or those who have risk factors for hypertension should have their blood pressure checked in both arms at least once a year by a doctor (rather than relying on an automatic machine at the pharmacy or grocery store). One reason: It’s important that the correct size blood pressure cuff is used.

Normal blood pressure is considered to be less than 120/80 mm Hg. With 24-hour monitoring or frequent home blood pressure monitoring, daytime normal blood pressure is defined as an average blood pressure less than 135/85 mm Hg.

If your numbers are higher than this, it does not mean you have high blood pressure. Blood pressure can change in response to exercise, stress, medication, illness, and even the time of day. It’s important to take several readings over time in order to make an appropriate diagnosis.


Most adults with high blood pressure have primary hypertension (once known as “essential” hypertension). This simply means that the elevation in blood pressure is not due to any other cause. Primary hypertension gradually develops over several years. Unless your blood pressure is monitored regularly, you may not be aware that you are experiencing a problem that could lead to significant organ damage.

Secondary hypertension refers to hypertension that is caused by another condition or medication. In most cases, secondary hypertension occurs suddenly and may cause a greater elevation in blood pressure than primary hypertension. Thyroid disorders, kidney disease, obstructive sleep apnea, alcohol abuse, illegal drugs, and tumors of the adrenal gland are some of the causes of secondary hypertension.

Risk Factors

There are a variety of factors that can increase the risk of high blood pressure. Some of these are unavoidable:

  • After the age of 45, men are more likely than women to develop high blood pressure
  • In women, the risk increases after the age of 65
  • African Americans are at greater risk of hypertension; for this population, high blood pressure tends to develop earlier and cause more serious complications than for other groups

Other hypertension risk factors may be modified with changes in diet and lifestyle, including:

  • Being overweight
  • Sedentary lifestyle
  • Tobacco use
  • High sodium or low potassium diet
  • Excessive alcohol intake
  • Low levels of vitamin D
  • Stress (which can increase blood pressure temporarily and also, over time, lead to chronic hypertension)

Children have a lower risk of developing essential hypertension than adults do, but kids can develop high blood pressure as a result of other conditions. A child's blood pressure should be measured at each annual check-up and compared to other children of the same age group.


Blood pressure readings are organized into five categories:


The numbers: Systolic blood pressure between 120-139 mm Hg or diastolic blood pressure between 80 and 89 mm Hg.

What it means: Prehypertension carries an increased risk of cardiovascular disease and typically worsens over time. Treatment includes non-pharmacological measures, such as weight reduction, increased physical activity, avoiding excess alcohol, and restricting salt intake.

Stage I Hypertension

The numbers: Systolic blood pressure of 140 mm Hg to 159 mm Hg or diastolic blood pressure of 90 to 99 mm Hg.

What it means: If only one of these values is elevated, then the higher value determines the severity of hypertension.

Isolated Systolic/Diastolic Hypertension

The numbers: Systolic blood pressure greater than 140 mm Hg and diastolic pressure of less than 90 mm Hg. A diastolic pressure greater than or equal to 90 mm Hg coupled with a systolic pressure less than 140 mm Hg is considered isolated diastolic hypertension.

What it means: The systolic blood pressure is the best predictor of risk in people over 60. Studies show that there are significant benefits to treating blood pressure, particularly in patients with mild hypertension. Current recommendations suggest that blood pressure medication is initiated in patients with stage I hypertension, although it should be started earlier in people who have heart disease, diabetes, or chronic kidney disease.

Stage II Hypertension

The numbers: Systolic pressure of 160 mm Hg or greater or diastolic pressure of 100 mm Hg or greater.

What it means: Stage II hypertension may initially require more than one medication for treatment.

Malignant hypertension

The numbers: Over 180 mm Hg systolic or 120 mm Hg diastolic

What it means: Blood pressure increases quickly and produces end-organ damage; (extremely high blood pressure also known as hypertensive urgency or hypertensive emergency)

Malignant hypertension requires immediate medical care. Symptoms may occur as a result of organ damage, including confusion or mental status changes, blurred vision, seizures, shortness of breath, swelling, and chest pain due to angina, heart attack, or aneurysm.


The United States Preventive Services Task Force recommends ambulatory blood pressure measurement for accurate diagnosis of hypertension. Although you may have elevated blood pressure when measured in your doctor's office, this can be the result of "white coat hypertension." Screening by your healthcare provider may also miss "masked hypertension."

Ambulatory blood pressure readings taken over 12 or 24 hours tend to be more representative of a person's blood pressure status than one-off readings taken in a doctor's office. For that reason, they tend to result in fewer patients requiring treatment.

Other patients may have elevated blood pressure averages discovered with ambulatory monitoring that place them at risk for stroke and cardiovascular disease even when the readings obtained in a healthcare setting are normal.

If you are diagnosed with hypertension, your physician or healthcare provider may order laboratory tests to determine whether or not there is a secondary cause, such as a thyroid disorder or abnormality of the adrenal gland. You may need blood tests to measure electrolyte levels, creatinine, and blood urea nitrogen to determine if your kidneys are involved, or urinalysis to diagnose kidney damage or rule out kidney disorders that can be a secondary cause.

Lipid profiles to measure cholesterol levels may be necessary to assess your risk of cardiovascular diseases like heart attack and stroke. Imaging studies are used to identify possible tumors of the adrenal glands or damage to the kidneys.

If you are diagnosed with hypertension, you will also need an eye examination. An examination with an ophthalmoscope can determine the effect your blood pressure has had on the blood vessels in the eye and whether or not your retina has sustained damage.

In addition to an electrocardiogram (ECG) to evaluate possible heart damage, an echocardiogram may be used to see if your heart has become enlarged or if you have other cardiac problems related to hypertension, like blood clots or heart valve damage. Doppler ultrasound examination can be used to check the blood flow through the arteries to determine if they have narrowed, thus contributing to high blood pressure.


The initial treatment for hypertension includes changes in lifestyle and diet to eliminate or reduce contributing factors like obesity or a high sodium diet. Other important steps include kicking the habit if you smoke and cutting back on alcohol to one drink a day for women and two drinks a day for men.

Aerobic exercise has a beneficial effect on blood pressure. Evidence shows that brisk walking for at least 30 minutes several times a week is beneficial for lowering high blood pressure.

There are also a number of different medication classes available for the treatment of hypertension. The JNC 8 recommendations for treatment of blood pressure are based on evidence from multiple studies in many different populations. People with stage II hypertension may need initial treatment with two medications or a combination drug.

Follow-up is important. If you haven't reached your blood pressure goal after a month of treatment, your healthcare provider may increase your dose or add a different class of medication. After you reach your blood pressure goal, you must continue to monitor your response to treatment and development of any other conditions in order to prevent the progression of problems.


  • Heart attack
  • Stroke
  • Aneurysms
  • Heart failure
  • Kidney failure
  • Damage to blood vessels
  • Cognitive and memory problems
  • Eye damage and vision loss
  • Metabolic syndrome

The damage is cumulative over time. High blood pressure is rarely associated with symptoms, so it is often left untreated or overlooked until permanent and devastating organ damage has occurred. When blood pressure is increased, the walls of the arteries may become injured or stretched. Damage to the blood vessels can create weak regions that give rise to aneurysms or rupture.

Damage to the heart muscle can cause atrial fibrillation over time. Atrial fibrillation is an irregular heart rate that puts you at risk for stroke. High blood pressure can also tear the inner layer of the arteries, allowing the buildup of scar tissue that attracts cholesterol debris and platelets (blood cells that form clots).

Cholesterol build-up in damaged blood vessels is called a plaque. These plaques cause a narrowing of the arteries, which results in more work for the heart to pump adequate blood through the body.

Plaque can rupture under high pressure. This causes platelets to adhere and form a clot that can break off and travel throughout blood circulation, blocking oxygenated blood from reaching critical tissues. Additionally, these clots may break off and travel to other parts of the body, blocking blood flow and causing heart attacks or stroke. Clot formation also narrows the artery, making the heart work harder to pump blood with oxygen throughout the body.

Damage to the arteries from high blood pressure, including scarring and cholesterol build-up, results in a stiffening of the arteries. This causes the heart to work harder to push blood throughout the body. The heart is a muscle, and over time, it will become damaged and floppy as a result of high blood pressure. The chambers of the heart will enlarge and the muscular fibers will not be able to contract adequately to compensate, resulting in heart failure.

A Word From Verywell

Hypertension is a serious chronic disorder that can cause many harmful health effects over time. If you are an adult over the age of 20, you should have your blood pressure checked by your healthcare provider at your regular health visit. If you are over the age of 40, it's important to have your blood pressure checked annually. Remember, the reading you get from a manual machine or at the pharmacy may not be accurate.

Detecting high blood pressure early can prompt you to make healthy changes in your diet and lifestyle that will reduce your risk of serious disorders like stroke or heart attack. If you fall in a high-risk category, have your blood pressure checked today.

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