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What Is Blood Pressure?

We all need blood pressure to live. Without it, blood can't flow through our bodies and carry oxygen to our vital organs. But when blood pressure gets too high — a condition called hypertension — it can lead to serious medical problems.

Hypertension is usually more of a problem for adults, but teens and kids also can have it. Even babies can have high blood pressure. The good news is that many of the things that cause hypertension can be treated.

Blood pressure is basically how hard your heart needs to pump to move blood around your body. It's the result of two different forces:

  1. the force the heart creates as it pumps blood through the circulatory system
  2. the force that comes from the arteries resisting the blood flow

Blood pressure rises with each heartbeat and falls when your heart relaxes between beats, but there is always some pressure in the arteries.

Blood pressure can be affected by:

  • activity
  • rest
  • temperature
  • diet
  • emotions
  • posture
  • medicines

Why Is High Blood Pressure Bad?

High blood pressure means a person's heart and arteries must work harder than they normally would. Over time, the added stress can damage them. When the heart and arteries don't work as well as they should, other body parts (like the kidneys, eyes, and brain) may suffer.

Having high blood pressure makes people more likely to have strokes, heart attacks, heart failure, kidney failure, or loss of vision.

What Are the Signs of High Blood Pressure?

People can have high blood pressure for years and not have any signs. In rare cases, severe high blood pressure can cause problems like these:

  • headaches
  • vision changes
  • dizziness
  • nosebleeds
  • nausea (feeling sick)

A person with high blood pressure who has any of these problems should see a doctor right away.

How Do Doctors Measure Blood Pressure?

Blood pressure readings are fast and painless. Blood pressure is measured using an instrument called a sphygmomanometer (pronounced: sfig-mow-mah-NAH-meh-ter). This device has an inflatable cuff that a doctor or nurse wraps around your arm. As the cuff inflates, it squeezes an artery, stopping the blood flow for a moment. As the cuff deflates and the next heartbeat goes through the artery, the doctor or nurse measures the pressure. He or she also measures the pressure at its lowest point between heartbeats.

When doctors tell people their blood pressure, they use two numbers; for example, 120/80 ("120 over 80"). The first number is the systolic pressure. This is the pressure at the peak of each heartbeat. The second number is the diastolic pressure. This is the pressure when the heart rests between beats.

What Is Hypertension?

For adults (people 18 and older), blood pressure that's lower than 120 over 80 is normal. High blood pressure is 140 over 90 or higher. If someone's systolic pressure is 120 to 139, or if their diastolic pressure is 80 to 89, it's called prehypertension.

It's a little different for kids and teens: People younger than 18 have hypertension if 95% of kids or teens of the same age, height, and gender have lower blood pressure. Blood pressure between 90% and 95% of the normal range is considered prehypertension.

If a doctor or nurse thinks your blood pressure is too high, he or she will take at least three readings at different times before calling it hypertension. Teens with prehypertension or hypertension are more likely to have high blood pressure as adults.

What Causes It?

Most of the time, there's no specific reason why someone has high blood pressure. This is called essential hypertension or primary hypertension. But some people have a medical condition that causes hypertension — like kidney disease or a thyroid disorder. This is called secondary hypertension.

If you have high blood pressure, a doctor might also check for high blood cholesterol and other conditions that could make heart disease or a stroke more likely.

Other causes of high blood pressure include:

  • being obese
  • stress
  • lack of exercise
  • too much salt in the diet
  • using alcohol, tobacco, or illegal drugs
  • some medicines (like steroids or birth control pills)

How Do Doctors Diagnose Hypertension?

A single reading showing high blood pressure doesn't mean that you have hypertension. It is a sign to watch your blood pressure, though. Sometimes, blood pressure needs to be checked several times over a period of days or weeks to determine if someone has hypertension.

Some people have what's called "white coat hypertension." This means that their blood pressure goes up when they're at a doctor's office because they're nervous. When they feel more relaxed, their blood pressure usually goes down. To make sure high blood pressure readings aren't caused by anxiety, doctors will sometimes track a person's blood pressure over a whole day. This is called ambulatory blood pressure monitoring.

If you have high blood pressure, your doctor will want to figure out why. He or she might ask about:

  • your medical history
  • the health of your family members
  • any medicines or drugs you take
  • if you use tobacco or drink alcohol
  • your eating and exercise habits
  • if you've had any kidney problems

Your doctor will probably weigh and measure you. He or she might do urine tests or blood tests to check for other conditions that can cause hypertension.

How Is Hypertension Treated?

Some people need medicine to control high blood pressure. Often, though, people can manage hypertension by making changes in their lives; for example:

  • losing weight
  • eating healthier foods
  • getting more exercise
  • avoiding tobacco and alcohol

If you've been told you have hypertension, your doctor will work with you to come up with a treatment plan.

In some cases, teens with severe hypertension may need to be careful about the kinds of exercise they do. Some will have to avoid things like weightlifting and bodybuilding until their blood pressure is back to normal.

Can I Prevent It?

Here are ways to help prevent hypertension and keep yourself healthy:

  • Stay at a normal weight for your height.
  • Exercise for about an hour a day. This can help you control your weight and keep your blood pressure from going up as you get older.
  • Eat a healthy diet that includes mostly whole grains, low-fat dairy products, fruits, and vegetables.
  • Don't use alcohol, tobacco products, or illegal drugs.
  • Keep your stress levels in check. It may help to practice relaxation techniques such as breathing exercises.
  • Add less salt to your food and avoid fast food and other foods that are high in salt.
  • Know your blood pressure and have it checked regularly.

Reviewed by: Samuel S. Gidding, MD, and Rupal Christine Gupta, MD
Date reviewed: July 2014

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Related Resources:
American Heart Association
This group is dedicated to providing education and information on fighting heart disease and stroke. Contact the American Heart Association at: American Heart Association 7272 Greenville Ave. Dallas, TX 75231 (800) AHA-USA1
American Lung Association
The mission of this group is to prevent lung disease and promote lung health. Contact the group at: American Lung Association 61 Broadway, 6th Floor NY, NY 10006 (212) 315-8700
National Heart, Lung, and Blood Institute (NHLBI)
The NHLBI provides the public with educational resources relating to the treatment of heart, blood vessel, lung, and blood diseases as well as sleep disorders.