How is blood pressure measured?
Blood pressure is usually measured with a device that goes around your upper arm. This is often done in a doctor's office. But some people also check their blood pressure themselves, at home or at work.
A blood pressure measurement consists of 2 numbers. For instance, your blood pressure might be "140 over 90." The first (top) number is the pressure inside your arteries when your heart is contracting, also known as the systolic pressure. The second (bottom) number is the pressure inside your arteries when your heart is relaxed, also known as the diastolic pressure. The table shows how hypertension and normal blood pressure are defined by some professional medical societies (Table 1).
What is a home blood pressure monitor?
A home blood pressure monitor (or meter) is a device you can use to check your blood pressure yourself. It has a cuff that goes around your upper arm (figure 1). Some devices have a cuff that goes around your wrist instead, but these may not be as accurate. The monitor also has a small screen or dial that shows your blood pressure numbers.
There are also special monitors you can wear for a day or 2. These are different because they automatically check your blood pressure many times throughout the day and night, even while you are sleeping. If your doctor thinks you should use one of these devices, they will talk to you about how to wear it.
Why do I need to check my blood pressure at home?
If your doctor knows or suspects that you have high blood pressure, they might want you to check it at home. There are a few reasons for this. Your doctor might want to look at:
- Whether your blood pressure is the same at home as it is in the doctor's office. Many people have higher blood pressure in the doctor’s office compared to at home (known as “white coat hypertension”).
- How well your blood pressure medicines are working, and to potentially adjust these medicines
- To determine if your high blood pressure is resistant to medications
- Among other reasons
People who check their own blood pressure at home in addition to implementing other interventions to lower blood pressure may do better at lowering their pressure.
How do I choose a home blood pressure monitor?
When choosing a home blood pressure monitor, you will probably want to think about:
- Cost – Some devices cost more than others. You should also check if your insurance will help pay for your device.
- Size – It's important to make sure the cuff fits your arm comfortably. Your doctor or nurse can help you with this.
- How easy it is to use – You should make sure you understand how to use the device. You also need to be able to read the numbers on the screen.
You do not need a prescription to buy a home blood pressure monitor. You can buy them at most pharmacies or over the internet. Your doctor or nurse can help you choose the right device for you.
How do I check my blood pressure at home?
Once you have a home blood pressure monitor, please ask your doctor or nurse to check it to make sure it fits you and works correctly. They may also ask you to demonstrate to them how you are measuring your blood pressure at home. You may benefit from bringing this monitor into your doctor’s office once a year to make sure that it is still functioning.
When it's time to check your blood pressure:
- Go to the bathroom and empty your bladder first.
- Sit in a chair with your feet flat on the ground, without crossing your legs, and with your back supported.
- Try to breathe normally and stay calm. Refrain from exercise, smoking, or drinking caffeine for at least 30 minutes before measuring.
- It is recommended that in the morning, you take your blood pressure before taking any blood pressure-lowering medications.
- Keep your elbow at the level of your heart, and attach the cuff to your arm. Place the cuff directly on your skin, not over your clothing (best to wear short sleeve clothing when measuring). The cuff should be tight enough to not slip down, but not uncomfortably tight.
- Sit and relax for about 3 to 5 minutes with the cuff on.
- Follow the directions that came with your device to start measuring your blood pressure. This might involve squeezing the bulb at the end of the tube to inflate the cuff (fill it with air). With some monitors, you just need to press a button to inflate the cuff. When the cuff fills with air, it feels like someone is squeezing your arm, but it should not hurt. Then you will slowly deflate the cuff (let the air out of it), or it will deflate by itself. The screen or dial will show your blood pressure numbers.
- Stay seated and relax for a few minutes, then measure your blood pressure again.
How often should I check my blood pressure?
Your doctor or nurse will tell you how often to check your blood pressure, and when. Some people need to check their blood pressure twice a day, in the morning and evening.
Your doctor or nurse will probably tell you to keep track of your blood pressure by checking once in the morning and once in the evening for at least a week. Then they will look at the numbers. The reason for checking for at least a week is that it's normal for your blood pressure to change a bit from day to day, or at different times of day. For example, the numbers might change depending on whether you recently had caffeine, just exercised, or feel stressed. Checking your blood pressure over several days – or longer – will give your doctor or nurse a better idea of what your typical blood pressure is at home.
How should I keep track of my blood pressure?
Some blood pressure monitors will record your numbers for you, or send them to your computer or smartphone. If yours does not do this, you will need to write them down, and we recommend that you keep a log book for doing so. Your doctor or nurse can help you figure out the best way to keep track of the numbers.
What if my blood pressure is high?
Your doctor or nurse will tell you what to do if your blood pressure is high when you check it at home. If you get a number that is higher than normal, measure it again to see if it is still high. If it is very high (above a certain number, which your doctor or nurse will tell you to watch out for), or if you have any trouble breathing, chest pain, severe headaches, changes to your vision, or weakness or numbness, you should call your doctor right away or call 911 to be taken to the Emergency Room.
If your blood pressure is only a little high, your doctor or nurse might tell you to keep checking it for a few more days or weeks, and then call if it does not go back down. Then they can help you decide what to do next.
Blood Pressure Level
Top Number (Systolic)
Bottom Number (Diastolic)
180 or above
120 or above
Stage 2 Hypertension
140 to 179
90 to 119
Stage 1 Hypertension
130 to 139
80 to 89
120 to 129
79 or below
119 or below
79 or below
- These definitions are from the American College of Cardiology and the American Heart Association.
- "Elevated blood pressure" is a term doctors or nurses use as a warning. It means you do not yet have hypertension, but your blood pressure is not as low as it should be for good health.