What Is Blood Pressure?

Pressure in Arteries Used to Assess Cardiovascular Health

Blood pressure (BP) is the pressure of circulating blood on the walls of arteries. Doctors use BP readings to help evaluate cardiovascular health.

BP is measured as a systolic pressure (the top number) and a diastolic pressure (the bottom number). The normal range for systolic BP in adults is less than 120 millimeters of mercury (mm Hg), and the normal range for diastolic BP is less than 80 mm Hg—for a normal BP reading of less than 120/80 mm Hg.

What Is Blood Pressure?

BP is closely related to the force and rate of the heartbeat and the diameter and elasticity of the arterial walls.

Systolic Vs. Diastolic Blood Pressure

Systolic BP is the amount of pressure exerted against your artery walls as your heart contracts, pushing blood into the arteries. Diastolic BP measures the lowest pressure in your arteries as your heart maximally relaxes.

Blood pressure readings for adults fall into five categories:

Blood Pressure Stages
Blood Pressure Status Systolic Diastolic
Normal 120 80
Elevated 130-139 or  80-89
Hypertension Stage 1 140 or higher and/or 90 or higher
Hypertension Stage 2 140 or higher or 90 or higher
Hypertension Crisis 180 or higher and/or Higher than 120

High or Low Blood Pressure

Hypertension is when your BP is above normal. When BP is too high for too long, it can slowly and significantly harm your health. Often, people with hypertension have no symptoms, and thus may be unaware they have high BP.

Hypotension is when your BP is too low or below normal. It can cause fainting, dizziness, and fatigue. Low BP typically only presents a problem when it's linked to symptoms.

According to the American Heart Association, there is no specific number at which day-to-day BP is considered too low.  Within certain limits, it is ideal to keep your BP on the low side, as long as you aren't experiencing symptoms of low BP.

A blood pressure cuff at a doctor’s office.
A blood pressure cuff at a doctor’s office. Fuse/Getty Images

Symptoms of Abnormal Blood Pressure

You can even have hypertension for years without any symptoms. High BP can damage organs and arteries. This is why hypertension is called the “silent killer.”

Symptoms may appear, but only after BP has reached a crisis stage. At this stage, you may experience severe chest pain, severe headaches with blurred vision, nausea and vomiting, shortness of breath, and/or seizures. Often, high BP is identified during a routine physical exam.

Hypotension can cause symptoms, including:

  • Fainting
  • Dizziness or lightheadedness
  • Dehydration and excessive thirst
  • Rapid, shallow breathing
  • Blurred vision
  • Cold, clammy, pale skin
  • Depression
  • Nausea
  • Fatigue
  • Diminished concentration

How Blood Pressure Is Evaluated

A healthcare professional will take your BP with a pressure-measuring gauge that's attached to an inflatable cuff that's placed around your arm. It is important to have a proper fitting arm cuff to get a correct reading. Ideally, your BP should be measured in both arms.

Doctors confirm a diagnosis of hypertension over a series of separate appointments. They will take two to three readings at each visit before making a hypertension diagnosis.

Your doctor may also ask you to check your BP at home and keep a log of the readings or may ask you to wear a 24 hr BP monitor (known as ambulatory BP monitoring). They will do this for two reasons—people can have varying BP readings throughout the day, and it can be unusually elevated at doctors’ visits because of anxiety (white coat hypertension).

Hypotension is diagnosed based on BP measurements and symptoms.

Additionally, your evaluation of hypertension and hypotension may include:

  • Blood tests: These can provide information about your health and can identify underlying diseases.
  • Electrocardiogram (ECG): The test provides information about your heart function and can be used to detect irregularities in your heart rate and rhythm.
  • Tilt table test: If you experience low BP, a tilt table test may determine how your body responds when changing position.

Causes and Risk Factors

There are numerous causes and risk factors for abnormal BP.

Causes of hypertension include:

  • BP increases with age.
  • Blacks are more prone to hypertension as well as conditions linked to it.
  • Hypertension runs in families.
  • High body mass index (BMI) or obesity
  • Unhealthy diet
  • Smoking
  • Excessive alcohol
  • Sedentary lifestyle
  • Stress
  • Medication
  • Pregnancy
  • Cushing's disease
  • Hyperaldosteronism
  • Potassium or magnesium deficiencies
  • Chronic kidney disease
  • Renal artery stenosis
  • Rarer endocrine disorders

Causes of hypotension include:

  • Heart problems
  • Dehydration
  • Blood loss
  • Severe infection (sepsis)
  • Severe allergic reaction (anaphylaxis)
  • Endocrine problems
  • Malnutrition
  • Pregnancy
  • Certain medications

Treatment

Treatment for high BP includes lifestyle changes, medications, or both.

A healthy, low-sodium diet, smoking cessation, exercise, and weight loss are ways to lower BP on your own. Your doctor may also need to prescribe BP-lowering medication for you to take.

Low BP that doesn’t cause symptoms or causes only a few symptoms rarely requires treatment. Treatment depends on the cause of your hypotension.

If there is no diagnosable cause of your hypotension, your doctor may recommend the following to raise your BP:

  • Eat more salt: Sodium can help raise BP in some people with hypotension. For older adults, too much salt can lead to heart failure, so it’s key to check with a doctor first before increasing your salt intake, even if you have hypotension.
  • Drink more fluids: Water increases blood volume and prevents dehydration. Both are important steps in treating hypotension.
  • Lifestyle changes: Wear compression stockings, avoid standing for a long time, and get up slowly when rising to stand.
  • Medications: Your doctor can prescribe medications to increase your blood volume or raise your BP.

Complications

Abnormal blood pressure makes puts you at risk for other health conditions. This is why it is important for you to get treated for your hypertension early.

Uncontrolled hypertension can cause:

  • Hardening and narrowing of the arteries, which makes the heart work harder
  • Damage to the heart, brain, eyes, and kidneys
  • Heart attack, heart failure, and stroke
  • Kidney disease
  • Dementia
  • Aneurysm

A Word From Verywell

It is important to know your blood pressure reading throughout your life. The good news is if your blood pressure becomes abnormal, there are lifestyle changes and medications available to keep it under control. If you have concerns or more questions about your blood pressure, contact your doctor.

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Article Sources
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