What is systolic vs. diastolic blood pressure?

In this article:

• The bottom line
• Systolic vs. diastolic blood pressure
• Which is more important, diastolic or systolic blood pressure?
• How blood pressure is measured
• Systolic vs. diastolic normal range
• Blood pressure normal ranges in adults (measured in mmHg)
• Maintaining healthy systolic and diastolic blood pressure
• The bottom line 

In this article

• The bottom line
• Systolic vs. diastolic blood pressure
• Which is more important, diastolic or systolic blood pressure?
• How blood pressure is measured
• Systolic vs. diastolic normal range
• Blood pressure normal ranges in adults (measured in mmHg)
• Maintaining healthy systolic and diastolic blood pressure
• The bottom line 

High blood pressure, or hypertension, is a very common health condition affecting almost half of adults in the U.S. Having high blood pressure increases the risk for problems like heart attack and stroke, which are leading causes of death. 

A blood pressure reading is given in two numbers: systolic and diastolic pressure. Your healthcare provider may tell you that your blood pressure goal is 120/80 mm Hg, for example, but what does that mean? What do the systolic and diastolic numbers mean regarding blood pressure? In general terms, the top number is the systolic pressure—it’s the measure of how much pressure the blood exerts against the artery walls when the heart is contracting. The bottom number is the diastolic pressure, it is a measure of how much pressure the blood exerts against the artery walls when the heart muscle rests between contractions. 

Systolic vs. diastolic blood pressure

First, let’s go over some definitions before talking about blood pressure.

• Blood vessels carry blood through the body. They form a closed loop, beginning and ending at the heart. The types of blood vessels are arteries, veins, and capillaries.
• Arteries carry blood away from the heart.
• Veins carry blood to the heart.
• Capillaries are the smallest blood vessels. They connect the arteries and veins.

Blood pressure is the measure of the pressure of blood that pushes against the walls of the arteries. It is measured and reported as systolic pressure and diastolic pressure. The units are called mmHg, or millimeters of mercury.

• Systolic blood pressure (systolic BP) is the first number (or the top number), and it measures the pressure in the arteries when the heart beats.
• Diastolic blood pressure (diastolic BP) is the second number (or bottom number), and it measures the pressure in the arteries as the heart rests between beats.

The pulse pressure is the difference between the two numbers and can indicate possible health conditions before they develop. To calculate the pulse pressure, subtract the bottom number from the top number. So, if your blood pressure is 130/80 mmHg, your pulse pressure is 130 – 80, or 50. A comprehensive, or high, pulse pressure indicates a wide difference between the top and bottom numbers. People with a wide pulse pressure who do not get a lot of physical activity can be at risk for serious health conditions. As pulse pressure increases over 40, the risk of heart and blood vessel problems (such as heart disease, heart rhythm conditions, and stroke) increases.

Which is more important, diastolic or systolic blood pressure?

Both numbers are used to diagnose high blood pressure, although healthcare professionals may put more focus on the systolic (top) number. Although both numbers are important, studies show a higher risk of heart disease and stroke associated with higher systolic pressure than elevated diastolic pressure, especially in adults 50 or older. Most people have an increased systolic pressure with age due to stiffening of the arteries. 

Studies have shown that, especially in individuals under 50 years old, diastolic pressure readings provide additional information—in addition to the systolic, which is also very important in this age group. Experts note that it is important to consider both systolic and diastolic pressure, especially in those under 50 years old. Healthcare professionals also take pulse pressure into consideration. 

Because your doctor knows your medical and family history, you can ask for professional medical advice regarding the meaning of your blood pressure readings, as well as how often to check your blood pressure at home. 

How blood pressure is measured

It’s important to note that blood pressure can fluctuate over the course of the day. Some people get nervous when they go to the doctor and have higher blood pressure. Or, say you are running around and you are late for your appointment, and you are briskly walking from your car to the office. Your blood pressure may be temporarily elevated. This is why your blood pressure may be measured at the beginning of the visit as well as again during the visit. 

If you are having your blood pressure taken, the best way is for you to sit down and relax in a chair. Wait at least three minutes before measuring your blood pressure so that your body is at rest. Rest the upper arm (the one that the blood pressure cuff is placed on) on a table, at about the same height as the heart. 

Your healthcare provider will likely use a sphygmomanometer to measure your blood pressure. It has three parts:

• A cuff that goes around the arm and is inflated with air
• A meter to measure pressure
• A stethoscope to listen to the sound of blood flow through the brachial artery in the upper arm

The cuff is placed around the arm and inflated until blood cannot flow through the brachial artery, and then the air is slowly released. When the air pressure falls below the systolic blood pressure, blood will start to flow again, creating a pounding sound. When this sound is heard, it is recorded as the systolic blood pressure. When the pounding sound stops, the blood vessels remain open, and this is the diastolic blood pressure. 

Systolic vs. diastolic normal range

A normal blood pressure can vary from person to person, and it tends to increase with age—as age increases, the arteries become more stiff, causing higher blood pressure. In most cases, the target blood pressure for adults is less than 120/80 mmHg. Ask your healthcare provider what your target blood pressure should be, based on your individual medical history. The table below lists blood pressure ranges for adults. 

Maintaining healthy systolic and diastolic blood pressure

In addition to taking blood pressure medications, if prescribed, you can try some lifestyle changes that promote healthy blood pressure. Here are some tips from the American Heart Association: 

• Eat a healthy diet. Include lots of fruits and vegetables, whole grains, low-fat dairy, healthy oils, nuts, and lean poultry and fish. Limit salt and alcohol. The Dietary Approaches to Stop Hypertension (DASH) diet is one example of an eating plan that helps control blood pressure. A registered dietician can be a helpful resource in designing an eating plan that fits your lifestyle.
• Increase your physical activity. Check with your healthcare provider before beginning a new exercise program. Guidelines recommend at least 150 minutes per week of moderate-intensity physical activity (which can be broken up into 5, 30-minute sessions) plus two days of strength training exercise every week.
• Try to achieve and maintain a healthy weight. (See above bullets) Losing weight, if needed, can help control blood pressure and lower the risk of other serious health problems such as cardiovascular disease and stroke.
• If you smoke, stop smoking. Avoiding smoking, including secondhand smoke, can help decrease your risk for complications like heart attack and stroke.
• Manage stress. Try to find ways to reduce stress, such as therapy or finding time for relaxation. 
• Keep in communication with your healthcare provider. Monitor your blood pressure at home if your doctor recommends doing so, and report your numbers as requested. Take your medications as prescribed, and tell your doctor if you have any side effects or concerns about your medications. If price is a concern, you can always use free SingleCare cards or coupons to save up to 80% off the cost of your medicines.

The bottom line 

To recap, blood pressure is reported as two numbers. The first is the systolic pressure, which measures the pressure in the arteries when the heart beats. The second number is the diastolic pressure, which measures the pressure in the arteries as the heart rests between beats. Monitoring and controlling high blood pressure is important in staying healthy and preventing other health conditions and complications. 

If you have hypertension, you should follow up regularly with your healthcare professional. However, even if you have not been diagnosed with hypertension, you should have your blood pressure checked at regular intervals, especially if another individual in your family has high blood pressure. Ask your healthcare provider for more information and personalized medical advice.