What do the blood pressure numbers mean?

Blood pressure measurements are written as a pair of numbers: The systolic pressure (the top number) is a measure of the pressure the blood exerts against the arterial walls when the heart contracts. The diastolic pressure (the bottom number) is the pressure between contractions. Normal blood pressure is considered to be less than 120/80 millimeters of mercury (mm Hg).

Blood pressure is typically expressed as two numbers, one over the other, and is measured in millimeters of mercury (noted as mm Hg). The first number is the systolic blood pressure, the pressure used when the heart beats. The second number, diastolic blood pressure, is the pressure that exists in the arteries between heartbeats.Depending on your activities, your blood pressure may increase or decrease throughout the day. If you are not acutely ill, are over 18 years of age and are not taking antihypertensive drugs, a blood pressure reading of 119 mm Hg or below systolic and/or 79 mm Hg or below diastolic (119/79) is considered normal. If your systolic blood pressure is 120 to 139 mm Hg systolic and/or your diastolic pressure is 80 to 89 mm Hg, you have prehypertension. This means that you don't have high blood pressure now but are more likely to develop it in the future, and you have increased risk factors for cardiovascular disease and other conditions related to hypertension.

A blood pressure level of 140/90 mm Hg or higher is considered high. You have stage 1 hypertension if your systolic pressure is 140 to 159 and/or diastolic is between 90 and 99. If your systolic pressure is 160 or above and/or your diastolic is100 or more, you have stage 2 hypertension. Only one of the numbers needs to be above normal for a diagnosis of high blood pressure; that is, you can have isolated systolic or diastolic hypertension. Isolated systolic hypertension (ISH) is the most common form of high blood pressure in older Americans. The National Heart, Lung, and Blood Institute (NHLBI) estimates that 65 percent of people with hypertension over age 60 have ISH. The cause of approximately 90 to 95 percent of all hypertension isn't known. This type of hypertension is called primary or essential high blood pressure. Secondary hypertension is somewhat different because it represents all of the specific diseases that cause elevated blood pressure. It is important to diagnose this type of hypertension because the treatment differs from primary hypertension.

You should have your blood pressure checked whenever you see a healthcare professional. Because blood pressure can be variable, it should be checked on several different days before a high blood pressure diagnosis is made. One elevated blood pressure reading doesn't necessarily mean you have high blood pressure, but it does warrant repeated measurements and means you have to watch your blood pressure carefully.

Blood pressure is recorded as systolic pressure over diastolic pressure. Systolic pressure is created during the contraction of the heart, while diastolic pressure is created during relaxation. A normal blood pressure is less than 120 systolic and less than 80 diastolic, or 120/80.

Dr. Ozgen Dogan
Cardiologist (Heart Specialist)

The higher number in your blood pressure reading is your systolic blood pressure. That number represents the amount of pressure in your arteries when your heart is beating. The lower number is your diastolic blood pressure. That's the amount of pressure in your arteries when your heart is at rest, meaning between heartbeats.

Dr. Joel H. Fuhrman, MD
Family Practitioner

Systolic is the first, higher number; it represents the force of the heart pumping against the resistance offered by the blood vessels walls. Diastolic is the second, lower number; it represents the pressure against the blood vessels during the relaxation and filling phase of the heart beat. When blood vessels stiffen with disease and aging, the systolic rises because the vessels does not expand during systole like they should, and the diastolic falls as the blood vessel wall no longer contracts inward like it should.

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The first number (systolic) measures pressure while the heart beats. The second number (diastolic) measures pressure between heartbeats, as blood flows throughout the body.

Dr. Dianne L. Zwicke, MD
Cardiologist (Heart Specialist)

Blood pressure is the pressure inside the arteries (blood vessels). It is measured in two numbers, such as 110/70 (110 over 70).

  • The first or top number (systolic pressure) is the highest pressure in the arteries when the heart pumps blood into them.
  • The second or bottom number (diastolic pressure) is the lowest pressure when the heart rests to refill between beats.

Adults 18 years and older:

  • When your blood pressure stays below 120/80 at rest—You have a healthy blood pressure. A healthy lifestyle will help you keep it this way.
  • When your blood pressure stays between 120/80 and 139/89 at rest—You are at increased risk for health effects from high blood pressure. Your health care provider may ask you to make changes in your diet, activity, or other lifestyle habits.
  • When your blood pressure stays over above 140/90 at rest (or stays over above 130/80 if you have diabetes, heart failure, or kidney disease)—This is more serious and may require additional treatment (including medications) in addition to lifestyle changes. The higher your blood pressure, the greater your risk for wear and tear on your arteries, heart disease, and other health problems.

Your blood pressure reading has two parts. The first and higher number (systolic blood pressure) represents the pressure while the heart is beating and shows how hard the heart works to push blood through the arteries. The second and lower number (diastolic blood pressure) represents the pressure when the heart is relaxing and refilling with blood between beats and shows how forcefully arteries are being stretched most of the time.

The Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure defines normal blood pressure as below 120/80 millimeters of mercury (mm Hg), prehypertension as 120-139/80-89, hypertension stage 1 as 140-159/90-99, and hypertension stage 2 as greater than 160/100. If your systolic and diastolic pressures don't correlate to any one category—if, for example, your pressure is 130/75—your degree of hypertension will be based on the higher reading.

Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)

Your blood pressure consists of two numbers: The top or higher number is called the systolic number (pressure in vessels when your heart is beating), and the bottom or lower number is your diastolic number (pressure in your vessels when your heart is at rest). Here are the numbers you need to know:

  • Optimal blood pressure: 115/75
  • Prehypertension: 120-140
  • Hypertension (high blood pressure): Over 140/90

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Blood pressure measurements contain two numbers—the systolic (top) number and the diastolic (bottom) number. The systolic number is a measurement of the pressure when the heart pumps blood out to the body. The diastolic number measures the pressure in the arteries between heart beats, while the heart is filling up with blood.

Dr. Kathleen Handal, MD
Emergency Medicine Specialist

Let me explain in general terms what the blood pressure numbers mean: top number (the systolic blood pressure) is the pressure the heart has to overcome to open the valves to pump blood out. Bottom number (the diastolic blood pressure) is the pressure between beats when the heart is resting.

The “ideal” blood pressure for the average adult is 120/80. But understand that your blood pressure typically goes higher with age and activity. The normal blood pressure for a 30-year-old is different than the normal blood pressure for a 70-year-old.

The American Heart Association’s guideline for upper limit "normal" home blood pressure is systolic of 135 and or diastolic of 85. Newer home blood pressure machines have an indicator to alert you when a reading is greater than 135 for the systolic or 85 for the diastolic. A blood pressure reading of 140 over 90 or higher is considered elevated.

Your doctor can provide you with information on your normal range and parameters for when to seek medical assistance. If you are on medication to lower your blood pressure, you must know what blood pressure readings require you to hold your medication, to take additional medication, as well as when to go to the ER. For instance, if your blood pressure is 98/50 should you take your blood pressure lowering medication? The answer is most likely "no" because lowering your blood pressure any further could be life threatening. In this case, it would be best to call your doctor for advice.

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The higher (systolic) number represents the pressure while the heart contracts to pump blood to the body. The lower (diastolic) number represents the pressure when the heart relaxes between beats. The systolic pressure is always stated first and the diastolic pressure second. For example, 116/72: systolic = 116, diastolic = 72.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.