Measuring Blood Pressure

What is a blood pressure measurement?

Each time your heart beats, it pumps blood into your arteries (the blood vessels that carry blood from your heart to the tissues and organs in your body). A blood pressure measurement is a test that measures the force (pressure) in your arteries as your heart pumps. Blood pressure is measured as two numbers:

• Systolic blood pressure (the first and higher number) measures pressure inside your arteries when your heart beats.
• Diastolic blood pressure (the second and lower number) measures the pressure inside the artery when your heart rests between beats.

For example, a blood pressure reading of 120/80 means a systolic of 120 and a diastolic of 80.

Many things can change your blood pressure. It can increase or decrease based on:

• Whether you're resting or exercising
• If you eat or drink foods with caffeine, alcohol, or tobacco
• Your age
• If you're taking certain medicines
• Your position, such as whether you're sitting, lying down, or standing

If your blood pressure is high on several different measurements on different days, you might have high blood pressure, also known as hypertension. Around half of American adults have high blood pressure. It increases the risk of life-threatening conditions, including heart attack and stroke. But high blood pressure rarely causes symptoms. A blood pressure measurement helps diagnose high blood pressure early, so it may be treated before it leads to serious complications.

Other names: blood pressure reading, blood pressure test, blood pressure screening, sphygmomanometry

What is it used for?

A blood pressure measurement is most often used to diagnose high blood pressure.

Blood pressure that's too low, known as hypotension, is much less common. But you may get tested for low blood pressure if you have certain symptoms. Unlike high blood pressure, low blood pressure usually causes symptoms. These include:

• Dizziness or lightheadedness
• Nausea
• Cold, sweaty skin
• Pale skin
• Fainting
• Weakness

Why do I need a blood pressure test?

A blood pressure measurement is often included as part of a regular checkup. Everyone age 3 or older should have their blood pressure checked by their provider at least once a year.

If you have high blood pressure or are at higher risk for it, you may need testing more often. You may be at higher risk if you:

• Are 40 years old or older.
• Are overweight or have obesity.
• Have a family history of heart disease or diabetes.
• Have a family history of high blood pressure.
• Take birth control pills or other medicines that can increase your blood pressure.
• Are Black/African American. Black/African Americans are more likely than other racial and ethnic groups to have high blood pressure.

Your provider can tell you how often you should get your blood pressure checked.

You may also need to have your blood pressure checked:

• To see how well your blood pressure medicine is working (if you have high blood pressure)
• If you are being treated in the hospital
• To check if it's safe for you to have a medical or surgical procedure
• To check if it's safe for you to play sports or do other strenuous activities or jobs
• If you have symptoms of low blood pressure

What happens during a blood pressure test?

A blood pressure test includes the following steps:

• You will sit in a chair with your feet flat on the floor.
• You will rest your arm on a table or other surface, so your arm is level with your heart. You may be asked to roll up your sleeve.
• Your health care provider will wrap a blood pressure cuff around your arm. A blood pressure cuff is a strap-like device. It should fit snugly around your upper arm, with the bottom edge placed just above your elbow.
• Your provider will inflate the blood pressure cuff using a small hand pump or by pressing a button on an automated device.
• Your provider will measure the pressure manually (by hand) or with an automated device.
  • If done manually, they will place a stethoscope over the major artery (brachial artery) in your upper arm and elbow joint to listen to the blood flow and pulse as the cuff inflates and deflates.
  • If using an automated device, the blood pressure cuff automatically inflates, deflates, and measures pressure.
• As the blood pressure cuff inflates, you'll feel it tighten around your arm. This blocks the blood flow in that part of your arm for a short time.
• Your provider will then open a valve on the cuff to slowly release air. As the cuff deflates, blood flow will start again in your arm.
• As the pressure falls, a measurement is taken when the sound of blood pulsing is first heard. This is the systolic pressure.
• As the air continues to be let out, the blood pulsing sound will start to go away. When it completely stops, another measurement is taken. This is the diastolic pressure.

This test only takes about one minute to complete.

Your provider may also ask to take your blood pressure while you stand or lie down. They may also want to repeat the blood pressure measurement on your other arm.

Will I need to do anything to prepare for the test?

Several things can increase your blood pressure measurement. Tell your provider if you take any medicines, since some medicines may affect your results.

To get a more accurate blood pressure measurement, avoid these things for at least 30 minutes before having your blood pressure taken:

• Exercise
• Alcohol
• Tobacco products
• Food or drinks containing caffeine

Also, make sure to go to the bathroom before the test.

Are there any risks to the test?

You may have a little discomfort when the blood pressure cuff inflates and squeezes your arm. But this feeling only lasts for a few seconds.

What do the results mean?

Your results, also known as a blood pressure reading, will contain two numbers. The top or first number is the systolic pressure. The bottom or second number is the diastolic pressure. Blood pressure readings are also labeled by categories, ranging from normal to crisis. Blood pressure is measured in millimeters of mercury (mm Hg).

Your reading may show your blood pressure is:

Your blood pressure measurement can go up and down. Your provider will only usually diagnose you with high blood pressure if you have two or more high blood pressure readings on different days. They may also consider your blood pressure readings over a period of time, your medical and family history, and if you have other symptoms before diagnosing you with high blood pressure.

If your child is younger than 13, your provider will compare their blood pressure readings with what is common for children the same age, sex, and height.

If you've been diagnosed with high blood pressure, your provider may recommend:

• Lifestyle changes and/or medicines to control your blood pressure.
• You to regularly check your blood pressure at home with an automated blood pressure monitor. An at-home blood pressure monitor usually includes a blood pressure cuff and a digital device to record and display blood pressure readings.

At-home blood pressure monitoring is not a replacement for regular visits with your provider. But it can provide important information, such as whether your treatment is working or if your condition may have gotten worse.

Also, home monitoring may make the test less stressful. Many people get nervous about getting their blood pressure taken at a provider's office. This is called "white coat syndrome." It can cause a temporary rise in blood pressure, making the results less accurate.

To get the most accurate results when taking your blood pressure at home:

• Make sure the blood pressure cuff fits snugly but isn't too small.
• Use a blood pressure cuff that goes around your upper arm. It is more accurate than the ones that measure on your wrist or finger.
• Take your blood pressure at the same time of day each time.
• Rest in the chair for about five minutes before taking your blood pressure.
• Sit up straight with your legs uncrossed and your feet flat on the floor.

Seek immediate medical attention or call 911 if your blood pressure is over 180/120 mmHg, you have chest pain, shortness of breath, back pain, numbness or weakness, trouble speaking, or vision changes.

For more information about home monitoring of blood pressure, talk to your provider.

If you were tested for low blood pressure, a blood pressure reading of 90 systolic, 60 diastolic (90/60 mmHg) or lower is considered abnormal. Treatments for low blood pressure may include medicines and certain dietary changes.

Seek immediate medical attention or call 911 if you have symptoms of extremely low blood pressure, such as confusion, a weak and rapid pulse, or cold skin.

Is there anything else I need to know about a blood pressure measurement?

If you were diagnosed with high blood pressure, your provider may recommend some lifestyle changes such as:

• Getting regular physical activity. Staying active can help lower your blood pressure and also help manage your weight. Check with your provider before beginning an exercise program.
• Being at a healthy weight. Losing as little as 5 pounds can lower your blood pressure if you are overweight.
• Eating a healthy diet that includes fruits, vegetables, and whole grains. Limit foods high in saturated fat and total fat. The DASH eating plan is a heart-healthy style of eating.
• Reducing salt in your diet. Most adults and children over age 14 should have less than 2,300 mg of salt per day.
• Limiting alcohol use. Talk to your provider about how much alcohol you drink. They may recommend that you reduce the amount of alcohol you drink or that you stop drinking alcohol.
• Quitting smoking (if you smoke).
• Managing stress.
• Getting enough good-quality sleep.