Understanding Blood Pressure Readings

Updated:Oct 5,2017
Know your numbers

What do your blood pressure numbers mean?
The only way to know (diagnose) if you have high blood pressure (HBP or hypertension) is to have your blood pressure tested. Understanding your blood pressure numbers is key to controlling high blood pressure.

Healthy and unhealthy blood pressure ranges
Learn what’s considered normal, as recommended by the American Heart Association.

Blood Pressure
Category
Systolic
mm Hg (upper #)
 Diastolic
mm Hg (lower #)
Normalless than 120 andless than 80
Prehypertension120139or8089
High Blood Pressure
(Hypertension) Stage 1
140159 or9099
High Blood Pressure
(Hypertension) Stage 2
160 or higheror100 or higher
Hypertensive Crisis
(Emergency care needed)
Higher than 180
or
Higher than 110

Note: A diagnosis of high blood pressure must be confirmed with a medical professional. A doctor should also evaluate any unusually low blood pressure readings. Additionally, lower targets may be appropriate for some populations such as African-Americans, the elderly, or patients with underlying issues such as diabetes mellitus or chronic kidney disease.


Blood pressure categories
The five blood pressure ranges as recognized by the American Heart Association are:

  • Normal blood pressure
    Congratulations on having blood pressure numbers that are within the normal (optimal) range of less than 120/80 mm Hg. Keep up the good work and stick with heart-healthy habits like following a balanced diet and getting regular exercise.
     
  • Prehypertension (early stage high blood pressure)
    Prehypertension is when blood pressure is consistently ranging from 120-139/80-89 mm Hg. People with prehypertension are likely to develop high blood pressure unless steps are taken to control it.
     
  • Hypertension Stage 1
    Hypertension Stage 1 is when blood pressure is consistently ranging from 140-159/90-99 mm Hg. At this stage of high blood pressure, doctors are likely to prescribe lifestyle changes and may consider adding blood pressure medication.
     
  • Hypertension Stage 2
    Hypertension Stage 2 is when blood pressure is consistently ranging at levels greater than 160/100 mm Hg. At this stage of high blood pressure, doctors are likely to prescribe a combination of blood pressure medications along with lifestyle changes.
     
  • Hypertensive crisis
    This is when high blood pressure requires emergency medical attention. If your blood pressure is higher than 180/110 mm Hg and you are NOT experiencing symptoms such as chest pain, shortness of breath, back pain, numbness/weakness, changes in vision or difficulty speaking, wait about five minutes and take it again. If the reading is still at or above that level, you should CALL 9-1-1 and get help immediately. Learn more about the two types of hypertensive crises.

Your blood pressure numbers and what they mean
117 over 76 millimeters of mercuryYour blood pressure is recorded as two numbers:

  • Systolic blood pressure (the upper number) — indicates how much pressure your blood is exerting against your artery walls when the heart beats.
     
  • Diastolic blood pressure (the lower number) — indicates how much pressure your blood is exerting against your artery walls while the heart is resting between beats.

Which number is more important?
Typically, more attention is given to systolic blood pressure (the top number) as a major risk factor for cardiovascular disease for people over 50. In most people, systolic blood pressure rises steadily with age due to the increasing stiffness of large arteries, long-term build-up of plaque and an increased incidence of cardiac and vascular disease.

However, elevated systolic or diastolic blood pressure alone may be used to make a diagnosis of high blood pressure. And, according to recent studies, the risk of death from ischemic heart disease and stroke doubles with every 20 mm Hg systolic or 10 mm Hg diastolic increase among people from age 40 to 89.


Why blood pressure is measured in mm Hg
The abbreviation mm Hg means millimeters of mercury. Why mercury? Mercury was used in the first accurate pressure gauges and is still used as the standard unit of measurement for pressure in medicine.


Watch this video on what blood pressure numbers mean:


Taking your pulse versus checking your blood pressure
Your blood pressure and heart rate (pulse) are two separate measurements and indicators of health. Learn more about the difference between blood pressure and heart rate.

This content was last reviewed October 2016.

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