Diastole vs. Systole: Know Your Blood Pressure NumbersMedically Reviewed by Nayana Ambardekar,MD on August 29, 2020
In this Article
What Systolic, Diastolic Blood Pressure Numbers Mean
When you get your blood pressure numbers, there are two of them. The first, or top one, is your systolic blood pressure. The second, or bottom, one is diastolic blood pressure.
Knowing both is important and could save your life.
What Does the Systolic Blood Pressure Number Mean?
When your heart beats, it squeezes and pushes blood through your arteries to the rest of your body. This force creates pressure on those blood vessels, and that's your systolic blood pressure.
Heres how to understand your systolic blood pressure number:
What Does the Diastolic Blood Pressure Number Mean?
The diastolic reading, or the bottom number, is the pressure in the arteries when the heart rests between beats. This is the time when the heart fills with blood and gets oxygen.
This is what your diastolic blood pressure number means:
Our chart below has more details.
Even if your diastolic number is normal (lower than 80), you can have elevated blood pressure if the systolic reading is 120-129.
Blood Pressure Ranges
If you have normal blood pressure, your blood pressure is less than 120/80. Stick with an active lifestyle and healthy diet to keep that going.
Is your blood pressure above the normal range, in either or both systolic and diastolic levels? Your doctor will want to have more than one blood pressure reading before diagnosing hypertension.
Treatments include lifestyle changes, and if thats not enough, may also include medications.
Lifestyle changes include:
If you also need medication to lower your blood pressure, there are several types:
If you need medication, your doctor will consider which type is best for you. (Theyll also recommend lifestyle habits that help lower blood pressure.) Deciding whether you need medication is often done on a case-by-case basis, depending on what else is going on with your health and on your preferences.
If you have:
One reading may not be enough to diagnose high blood pressure. Your doctor may want you to have several blood pressure readings over time, to check if its consistently too high.
How Blood Pressure Is Measured
A doctor or nurse will measure your blood pressure with a small gauge attached to an inflatable cuff. It's simple and painless.
The person taking your blood pressure wraps the cuff around your upper arm. Some cuffs go around the forearm or wrist, but often they aren't as accurate.
Your doctor or nurse will use a stethoscope to listen to the blood moving through your artery.
Theyll inflate the cuff to a pressure higher than your systolic blood pressure, and it will tighten around your arm. Then theyll release it. As the cuff deflates, the first sound they hear through the stethoscope is the systolic blood pressure. It sounds like a whooshing noise. The point where this noise goes away marks the diastolic blood pressure.
In a blood pressure reading, the systolic number always comes first, and then the diastolic number. For example, your numbers may be "120 over 80" or written as 120/80.
When to Check Blood Pressure
Checking Blood Pressure at Home
Keeping track of blood pressure at home is important for many people, especially if you have high blood pressure. This helps you and your doctor find out if your treatment is working.
Your doctor may also suggest that you check your pressure at home if they think you may have "white coat hypertension." It's a real condition. The stress of being in a doctor's office raises your blood pressure, but when you're home, it's normal.
Ask your doctor to recommend an easy-to-use home blood pressure monitor. Make sure the cuff fits properly. If your arm is too big for the cuff, the reading may be higher than your blood pressure really is. Ask your doctor for a larger cuff or make sure you buy a home monitor with a cuff that fits you.
You also can use a wrist blood pressure monitor, but they often aren't as accurate. Follow the directions that come with the device to make sure you are using it correctly.
No matter which type of blood pressure monitor you have, it's a good idea to take it to your doctor's office. You can compare its reading to the numbers your doctor gets. Avoid caffeine, cigarettes, and exercise for at least 30 minutes before the test.
When you take your blood pressure at home, sit up straight in a chair and put both feet on the floor. Ask your doctor or nurse to show you the right way to position your arm so you get accurate readings.
Check it at the same time of day so the readings are consistent. Then, take several readings about 1 minute apart. Be sure to write down the results.
Take the blood pressure journal to your doctor's office so you can talk about any changes in your numbers. Your doctor will decide whether you need medications in addition to lifestyle changes.
Even if your blood pressure is high, you probably won't have symptoms. That's why it's often called the "silent killer." The first symptom of untreated high blood pressure may be a heart attack, stroke, or kidney damage.
Preventing High Blood Pressure
To keep your blood pressure in the normal range, your daily habits are key. These things help:
Dont smoke. Among the many health problems that smoking causes, it raises your blood pressure.
Make physical activity a habit. Most experts recommend at least 30 minutes of moderate-intensity physical activity (like biking or brisk walking) five or more times a week. Or you could do a harder activity for a shorter period of time per session.
Eat right. Read food labels to see how much sodium is in a serving. Check with your doctor to find out what your daily limit should be. Include a lot of vegetables and fruits, along with whatever else you choose to put on your plate.
Stick to a healthy weight. Extra pounds raise your blood pressure. If youre not sure what a healthy weight would be for you, ask your doctor.
Get enough sleep. For most adults, thats 7-8 hours of sleep per night, on a regular basis.
If you drink alcohol, limit it to no more than one drink a day if youre a woman and up to two drinks a day if youre a man.
JAMA, Patient Page: "Hypertension."
American Heart Association: "Understanding Blood Pressure Readings," "What is High Blood Pressure?"
AHA HeartHub for Patients: "High Blood Pressure."
JAMA:"The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure."
American College of Cardiology: "2017 Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults."
UpToDate: Overview of hypertension in adults.
CDC: Prevent High Blood Pressure.
U.S. Department of Health and Human Services, MyHealthFinder: Get Enough Sleep.
American Heart Association: Types of Blood Pressure Medications.