What Is Blood Pressure, Exactly?

Knowing what blood pressure is can help you better understand what healthy blood pressure looks like.
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Your blood pressure isn't just a number on your chart at the doctor's office — it's also one of the most important indicators of how healthy you are and how healthy you are likely to be in the future.

But what is blood pressure, exactly? In the simplest terms, it's the measure of how hard your blood is pressing on the walls of your arteries as your heart pushes it through your body, according to the American College of Cardiology (ACC).

"Blood pressure is the driving force for delivering blood to all of our organs," Karol Watson, MD, PhD, spokesperson for the American College of Cardiology (ACC) and co-director of the UCLA Program in Preventive Cardiology, tells LIVESTRONG.com.

Dr. Watson likens it to the pressure of a garden hose: You don't want it to be a trickle, but you also don't want it on full-blown, fire-hose level. "You need a nice, steady stream of blood," she says.

Here's what else you need to know about this key measure of your health.

Why Is Blood Pressure Important?

That steady stream of blood delivers oxygen and other nutrients that all the different parts of your body need to survive.

"Blood pressure is critical," says Michael Blaha, MD, MPH, professor of medicine and director of clinical research at Johns Hopkins University's Ciccarone Center for the Prevention of Cardiovascular Disease, adding that blood pressure needs to be high enough to sustain your everyday functions. "There is a blood pressure below which you can't live."

On the other hand, uncontrolled high blood pressure — also called hypertension — can kill you over time by damaging your blood vessels and organs, according to the ACC.

Read more: How Does Cinnamon Reduce Blood Pressure?

Systolic vs. Diastolic Blood Pressure

Your blood pressure measurement is given as two numbers — a larger number "over" a smaller number, like "120 over 80" or "120/80."

The first, higher number is called your systolic blood pressure, which measures the pressure when your heart is actually beating or pumping, Dr. Blaha says.

The second, lower number is your diastolic pressure. This records the pressure when your heart is resting between pumps.

"Systolic blood pressure is probably more important because it's more often uncontrolled," Dr. Watson says. Uncontrolled or high systolic blood pressure is a red flag that you're at risk for heart disease, among other things, according to the American Heart Association (AHA).

Being physically active can help keep your blood pressure in a healthy range.
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What Is a Healthy Blood Pressure Range?

According to 2017 American College of Cardiology and American Heart Association guidelines, a healthy blood pressure is less than 120/80 mm Hg (that's millimeters of mercury, in case you were wondering). Anything above that is considered high and may require treatment.

Any reading below 90/60 is considered low blood pressure, per the Mayo Clinic, but this is generally only a concern if it's accompanied by symptoms, such as:

  • Cold, clammy, pale skin
  • Rapid breathing
  • Fainting
  • Blurred vision
  • Confusion, especially in older adults
  • Nausea
  • Fatigue

Blood Pressure Chart

Blood Pressure Category

Blood Pressure Range

Normal

Less than 120/80

Elevated

Systolic between 120-129 and diastolic less than 80

Stage 1 Hypertension (High Blood Pressure)

Systolic between 130-139 or diastolic between 80-89

Stage 2 Hypertension (High Blood Pressure)

Systolic at least 140 or diastolic at least 90

Hypertensive Crisis (may require hospitalization)

Systolic over 180 and/or diastolic over 120

Source: American College of Cardiology. (2017). "New ACC/AHA High Blood Pressure Guidelines Lower Definition of Hypertension"

Read more: What Is Normal for Blood Pressure?

Factors That Affect Blood Pressure

Many different factors can influence your blood pressure levels, per the Mayo Clinic, including:

  • Age (older individuals are more likely to have high blood pressure)
  • Family history
  • Physical activity
  • Body mass index
  • Smoking
  • Diet (especially how much salt you eat)
  • Diabetes
  • Kidney disease
  • Race (African-Americans have a higher risk of developing hypertension)
  • Stress
  • Potassium in your diet
  • Sleep apnea
  • Pregnancy
  • Certain medications, such as decongestants

Read more: How the DASH Diet Can Help Lower Blood Pressure

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Is This an Emergency?

To reduce the risk of spreading COVID-19 infections, it is best to call your doctor before leaving the house if you are experiencing a high fever, shortness of breath or another, more serious symptom.