Systolic and diastolic blood pressure make up the two numbers in a blood pressure reading (e.g., 120/80).
Systolic blood pressure, or the top number, is the amount of pressure experienced by the arteries while the heart is beating. Diastolic blood pressure (the bottom number) is the amount of pressure in the arteries while the heart is resting in between heart beats.
This article delves into the differences between systolic and diastolic blood pressure, why both numbers are important, and what your blood pressure readings mean.
Is My Blood Pressure Normal?
Why Your Blood Pressure Matters
When the heart beats, blood pulses through the arteries to travel throughout the body. However, it is not a steady stream like you might see from a garden hose.
The pulse of the blood flow and the pressure it exerts change from moment to moment. It's highest during the heartbeat (systolic pressure) and lowest between heartbeats (diastolic pressure).
Providers measure blood pressure using these numbers because it is a standard way of describing the force of the pulsing blood.
Your systolic and diastolic blood pressures are both important. If the readings are too high, you could have high blood pressure. If the readings are too low, there may not be enough blood flowing to your brain and other organs.
Furthermore, if there are changes in the difference between the two numbers, it's a clue that there could be a heart condition or other health problem.
How Can You Tell If You Have High Blood Pressure?
Systolic Blood Pressure
During a heartbeat, the heart pushes blood out into the arteries. Systolic pressure is the measure of this pressure within the arteries while the heart beats. This phase, known as systole, is the point at which blood pressure is the highest.
Systolic blood pressure is considered normal when the reading is below 120 mmHg (millimeters of mercury) while a person is sitting quietly at rest.
Systolic pressure below 90 mmHg is considered low and may require intervention and management from your healthcare provider. If you get multiple systolic pressure readings above 180 mmHg, it is considered dangerously high and should be addressed by your healthcare provider.
High Systolic Blood Pressure
The heart muscle pushes out blood with higher pressure when a person is exercising, under stress, or at any time when the heart rate is increased. The systolic pressure goes up with it.
In these cases, the increased pressure is normal. However, when the pressure is high while a person is resting, that is not normal and is considered high blood pressure.
Since your blood pressure can go up when you're active, it's important to take your blood pressure during periods of quiet rest to accuratelydiagnose high blood pressure (hypertension).
High systolic blood pressure is usually caused by the stiffening of the arteries, which makes the heart have to work harder to push blood through them.
Even within the high systolic pressure range, there are different stages:
- Systolic BP of 130-139 is Stage 1 hypertension, which may be reversed with temporary meds and lifestyle changes.
- Systolic BP of 140 or higher is Stage 2 hypertension, which can drastically increase the risk of stroke or heart attack, may require a prolonged regimen of medication.
- Systolic BP of 180 or higher means that you're in hypertensive crisis and should call your healthcare provider right away.
Your healthcare provider will help you determine the best course of action for treating your high systolic BP.
What Does It Mean If Only Your Systolic Blood Pressure Is High?
Low Systolic Blood Pressure
There is such a thing as too-low systolic pressure, however. When the reading is significantly below 90 mmHg, it's called hypotension. This can cause lightheadedness, dizziness, or fainting. If low blood pressure is not treated, it may cause organs like the kidneys to start shutting down.
Systolic hypotension can happen if the amount of blood in your body becomes too low. For example, low blood pressure can happen when you are severely dehydrated or when you have major bleeding. In these cases, there just isn't enough blood to push through the body.
Low blood pressure can also happen if the heart muscle is too weak to push blood normally—for example if the heart muscle is damaged (cardiomyopathy) or if the arteries suddenly widen too much (as invasovagal syncope, a reflex that causes fainting).
Sometimes, low blood pressure happens when you change positions suddenly. You may feel dizzy when you stand up because gravity is pulling blood down toward your feet. This is a common condition called orthostatic hypotension.
Why Does My Blood Pressure Go Down When I Stand Up?
Diastolic Blood Pressure
The heart rests between beats so it can refill with blood. The pause between beats is called diastole. Your diastolic blood pressure is the measurement during this pause before the next heartbeat.
Normal diastolic blood pressure during quiet rest is below 80 mmHg. If you have high blood pressure, the diastolic number is often higher even during quiet rest. Diastolic blood pressure is considered dangerously low when it is 60 mmHg or lower and dangerously high when it is 110 mmHg or over. If you receive multiple readings with these numbers, it's a good idea to call your healthcare provider.
Low diastolic pressure may be seen with dehydration or with severe bleeding. It also may happen if the arteries relax and widen.
There are also multiple stages of high diastolic blood pressure:
- Diastolic BP of 80-89 is Stage 1 hypertension, which may be reversed with temporary meds and/or lifestyle changes.
- Diastolic BP of 90 or higher is Stage 2 hypertension, which can drastically increase the risk of stroke or heart attack may require a prolonged regimen of medication.
- Diastolic BP of 120 or higher means that you're in hypertensive crisis and should call your healthcare provider right away.
Your healthcare provider will help you determine the best course of action for treating your high systolic BP.
Improving Blood Pressure Reading Accuracy
Your systolic and diastolic pressures change depending on your activity level, stress, fluid intake, and other factors.
You need to do your best to limit how these other factors might change your pressure when you're taking a blood pressure reading.
For the most accurate reading, check your blood pressure when you are in a calm, warm space after you have been able to rest quietly for at least five minutes.
You should be relaxed, with your arms at your sides, and the cuff should be placed on your arm at about the level of your heart. Your legs should be uncrossed, and your bladder should be empty, as both of these factors can affect your reading.
Measuring blood pressure this way is a challenge in a busy provider's office. Your provider might suggest you take your blood pressure at home.
What Time of Day Should I Check My Blood Pressure?
Many experts suggest recording blood pressures that are taken over an extended time (which can include repeating the measurements at home) before diagnosing high blood pressure.
You should also know that your blood pressure will be different throughout the day. It tends to be highest in the morning and lower at night.
Your provider may want you to take your use a blood pressure monitor multiple days a day—usually once in the morning and once in the afternoon or evening. Try to avoid taking it early in the morning right when you wake up or right after dinner.
Instead, try to take your morning reading before your breakfast (especially if you drink coffee or take medication) and your evening reading when you're getting ready for bed (and again, before you take any medications).
Once you decide what time you'll check your blood pressure, it's important that you're consistent. You'll get the most accurate results and comparisons if you take your blood pressure at about the same time every day.
What Should My Blood Pressure Be?
Your blood pressure is a measurement of the pressures in your arteries while your heart is beating (systolic) and between beats (diastolic). Both of these values are important for diagnosing and managing high blood pressure.
Systolic and diastolic blood pressure are also important to know for treating a range of conditions, including heart disease or severe blood loss. It's important to get an accurate blood pressure reading under calm, quiet conditions.
Why Your Blood Pressure Changes Throughout the Day
Frequently Asked Questions
Which is more important: Systolic blood pressure or diastolic blood pressure?
Both systolic and diastolic blood pressure readings give important information about your health. However, systolic pressure is the number your doctor pays the greatest attention to if it is high.
What is normal blood pressure by age?
A blood pressure below 120/80 mmHg is ideal for most healthy adults. Children and teens may have slightly lower normal blood pressure. For example, a blood pressure of 100/65 could be considered normal for a toddler and a healthy, active teen could have a blood pressure of around 115/70.
Older adults may also have higher or lower blood pressures that are considered normal. For example, a person who is in their 60s may have a blood pressure of around 130/60.
Learn More:Chart: Average Blood Pressure by Age(Video) Systolic Blood Pressure Is More Important Than Diastolic Blood Pressure
What is considered dangerously high blood pressure?
Dangerously high blood pressure, also known as a hypertensive crisis, is when systolic blood pressure (the top number) is 180 or higher or diastolic blood pressure (the bottom number) is 120 or more.
What is the best time to take your blood pressure?
The specific time you take your blood pressure is not as important as being consistent about it, day after day. That said, it is best to avoid taking a reading first thing in the morning, after you have a meal, or right after you take medication.
When Is the Best Time to Take Your Blood Pressure?
Why is it important to know both the systolic and diastolic blood pressure? ›
Researchers say the top and bottom number are important in blood pressure readings. Both the systolic and diastolic are indicators when it comes to the risk of heart attack and stroke. The new findings don't significantly change how high blood pressure is treated as medication currently works on lowering both numbers.Which is the most important of the two blood pressure readings? ›
The top number is more important because it gives a better idea of your risk of having a stroke or heart attack. Having a raised systolic blood pressure but normal or low diastolic blood pressure is called Isolated Systolic Hypertension (ISH).Why systolic blood pressure is the most important? ›
Having a high systolic blood pressure over time can increase the risk of strokes, heart disease and chronic kidney disease. The recommended goal for systolic pressure for adults younger than age 65 who have a 10% or higher risk of developing cardiovascular disease is less than 130 mm Hg.Which is the most important blood pressure reading systolic or diastolic? ›
Recent findings: Generally, in studies in which readings of systolic and diastolic blood pressure have been compared, systolic blood pressure has been a better predictor of risk.What is the relationship between systolic and diastolic blood pressure? ›
Blood pressure readings are given in two numbers. The top number is the maximum pressure the heart exerts while beating (systolic pressure). The bottom number is the amount of pressure in the arteries between beats (diastolic pressure).What is the significance of the two numbers quoted for blood pressure? ›
The first or top number is your systolic blood pressure. This is the amount of pressure in your arteries during the contraction of your heart muscle. The second or bottom number is your diastolic blood pressure. This is the lowest level your blood pressure reaches as your heart relaxes between beats.Which is the more important BP number? ›
Q. When I am monitoring my blood pressure, which number is most important — top, bottom, or both? A. While both numbers in a blood pressure reading are essential for diagnosing and treating high blood pressure, doctors primarily focus on the top number, also known as systolic pressure.What are the three most important in measuring blood pressure? ›
A sphygmomanometer has three parts: a cuff that can be inflated with air, a pressure meter (manometer) for measuring air pressure in the cuff, and. a stethoscope for listening to the sound the blood makes as it flows through the brachial artery (the major artery found in your upper arm).Which blood pressure readings are most accurate? ›
Intra-arterial measurement of BP is the most accurate method, capable of giving a continuous picture. Indirect recordings give a rough estimate of intra-arterial pressure but less information about the relationship between individual subjects and their environment.What if your systolic pressure is normal but your diastolic is high? ›
But, when your diastolic blood pressure is above 80mm Hg (considered high), and you have normal systolic blood pressure, it's called 'isolated diastolic blood pressure. A diet that's high in salt disrupts your body's natural sodium balance, causing your body to retain water.
What is the difference between systolic and diastolic pressure called? ›
Pulse pressure is the difference between your systolic blood pressure, which is the top number of your blood pressure reading, and diastolic blood pressure, which is the bottom number. Doctors can use pulse pressure as an indicator of how well your heart is working.Why is the first blood pressure reading always higher than the second? ›
Your first blood pressure reading will almost always be higher than the second due to a wide range of factors, both environmental and psychological. These factors include white coat syndrome, stress, and having a full bladder.What if systolic is high and diastolic is low? ›
If your systolic blood pressure is higher than 130 but your diastolic blood pressure is under 80, that's called isolated systolic hypertension. It's the most common kind of high blood pressure in older people.Which blood pressure measurement is the most ideal for optimal health? ›
ideal blood pressure is considered to be between 90/60mmHg and 120/80mmHg. high blood pressure is considered to be 140/90mmHg or higher.What are the two main determinants of blood pressure? ›
The two determinants of arterial blood pressure are the volume of renal output and the amount of salt and water in the system.Which is the most important test in the initial evaluation of hypertension? ›
In general, the evaluation of hypertension primarily involves accurately measuring the patient's blood pressure, performing a focused medical history and physical examination, and obtaining results of routine laboratory studies. A 12-lead electrocardiogram should also be obtained.Which three factors affect blood pressure readings? ›
- Being overweight or obese.
- Too much salt (sodium) in your diet.
- Too little potassium in your diet.
- Not being physically active.
- Drinking too much alcohol.
Blood pressure has a daily pattern. Usually, blood pressure starts to rise a few hours before a person wakes up. It continues to rise during the day, peaking in midday. Blood pressure typically drops in the late afternoon and evening.What causes false high blood pressure reading? ›
Acute meal ingestion, caffeine or nicotine use can all affect BP readings, leading to errors in measurement accuracy. If the patient has a full bladder, that can lead to an error in systolic BP of up to 33 mm Hg, and the white-coat effect can have an error of up to 26 mm Hg.What time of day is blood pressure lowest? ›
Blood pressure changes throughout the day. Your blood pressure is typically at its lowest right after waking up. It tends to vary by up to 30% across the day. This is because of hormone changes, activity level, and eating.
Can lack of sleep cause high blood pressure? ›
Insomnia is linked to high blood pressure and heart disease. Over time, poor sleep can also lead to unhealthy habits that can hurt your heart, including higher stress levels, less motivation to be physically active, and unhealthy food choices.Can lack of sleep cause high diastolic blood pressure? ›
The less you sleep, the higher your blood pressure may go. People who sleep six hours or less may have steeper increases in blood pressure. If you already have high blood pressure, not sleeping well may make your blood pressure worse.What does it mean if both systolic and diastolic are high? ›
Even higher blood pressure (with the systolic blood pressure 180 or higher, the diastolic blood pressure more than 120, or both) is called a hypertensive urgency if there are no related symptoms. Or it's called a hypertensive emergency if there are symptoms indicating damage to the brain, heart, or kidneys.What method gives you both a systolic and diastolic reading? ›
 Palpatory methods for BP recording give only systolic BP values which are used to get approximates of SBPs, while the auscultatory method is used to get both SBP and DBP readings.Why diastolic BP is clinically important? ›
High diastolic reading: Increases the risk of aortic disease. The aorta carries blood and oxygen from the heart to the abdomen and chest. People with an elevated diastolic reading are more prone to developing abdominal aortic aneurysm, an enlargement of the aorta that can lead to rupture and a high risk of death.Why is diastolic pressure clinically more important? ›
Observational studies have shown that isolated diastolic hypertension is linked to an increased risk of cardiovascular disease. It is more common in younger individuals, males, and those with high body mass index (people above a healthy weight).How do nurses determine systolic and diastolic blood pressure? ›
The manual blood pressure reading is obtained with a sphygmomanometer (aneroid manometer gauge and blood pressure cuff) and stethoscope. Once obtained, the nurse records it with the systolic reading (this is the first sound heard) over the diastolic blood pressure reading (the point when the sound stops).What artery do you listen to when taking blood pressure? ›
For a manual blood pressure measurement, the care provider places a stethoscope over the major artery in the upper arm (brachial artery) to listen to blood flow. The cuff is inflated with a small hand pump.What comes first diastolic or systolic? ›
When a person receives their blood pressure results, they will see two numbers that represent the diastole and systole measurements. These measurements are given as millimeters of mercury (mm Hg). The first number is the systolic pressure and the second is the diastolic pressure.Which is the most important number in blood pressure? ›
For years, systolic blood pressure has been seen as the one that really matters. That's based on studies -- including the famous Framingham Heart Study -- showing that high systolic blood pressure is a stronger predictor of heart disease and stroke.