Measuring your blood pressure at home

When is it useful to measure blood pressure at home?

Home blood pressure (BP) measurements can help:

• when your doctor thinks you might have white-coat hypertension (this is when someone with normal BP has raised BP due to anxiety from being measured in a clinical setting, such as at your doctor's surgery)
• when there is a big variation in your BP measurements between visits
• to check whether your medicine is working or if it's causing low blood pressure (hypotension)
• when you are not responding to blood pressure-lowering treatments.

Home blood pressure readings have a strong correlation with risk, in that the results more accurately indicate your risk of hypertension (high blood pressure) and the conditions associated with it.

Measuring your blood pressure at home is seen as having many advantages over measurement in your doctor's office for the management of hypertension (high blood pressure), especially if you have chronic kidney disease or diabetes.

How to choose a blood pressure measuring device

If you are measuring your BP at home, you need to:

• use a validated blood pressure measuring device (also called a BP monitor)
• measure your BP in a consistent manner.

Devices for home monitoring usually inflate automatically at the push of a button. There are some manual models that require you to inflate the cuff yourself by pumping a bulb. 

Devices that measure BP at your upper arm are generally considered more reliable than those that measure BP at your wrist or finger. Rarely, some people need to use a validated wrist device if you have a large arm. 

It's important to choose an appropriate cuff size. Cuffs are available in small, medium and large sizes. Using the wrong cuff size can give you incorrect BP readings. A cuff that is too small will overestimate BP and a cuff that is too large will underestimate BP.

If you are doubtful about the accuracy of your BP monitor, take it to your doctor's office or pharmacy so that staff can compare the monitor's reading to that of their own device.

Tips on how to measure your blood pressure

• It's best to measure your BP in a quiet room after you've been sitting for 5 minutes. Your arm should be relaxed. 
• Sit with your feet flat on the floor, legs uncrossed, upper arm bare, back and arm supported in a relaxed position, with the cuff at heart level.
• Take 2 consecutive measurements for systolic and diastolic pressure, 1–2 minutes apart. Taking one set of measurements is not enough.
• If your doctor asks you to record your standing BP, wait at least 2 minutes after standing to record your BP.
• Take morning measurements before breakfast and before taking any medicines.
• Take evening measurements before going to bed and after taking any medicines.
• Record any obvious reasons for variations, such as if you are unwell, your caffeine intake, smoking, a poor night's sleep or recent exercise.

Your BP changes throughout the day, depending on the time of day, what you are doing and any stress or excitement you are feeling. Fluctuations in BP are normal. Caffeine and tobacco smoke can increase BP and measurements are best at least 30 minutes before or after these stimulants.

Recording your blood pressure

Some BP monitors have the provision to record your BP readings, but you may prefer to keep a paper diary or use a BP app to record your BP measurements. Read more about blood pressure apps

Things to avoid

Avoid measuring your BP when you are uncomfortable, stressed, in pain or affected by extremes in temperature, such as a poorly heated home during winter.

• Some people with raised blood pressure may become anxious due to continually high readings. These feelings of anxiety can affect your BP measurements. Talk to your doctor if this happens to you.
• Some people may become obsessed with their blood pressure and take an excessive number of recordings. Talk to your doctor if this happens to you.

BP apps

Avoid mobile phone apps that claim to be able to measure BP without the use of a blood pressure cuff. These apps are not validated and are not recommended for the diagnosis or management of hypertension. Read more about blood pressure apps.

Changes to your medicines

Do not make changes to your BP medicines based on your BP readings without consulting your doctor.

Learn more

The following links have more information on measuring your BP at home. Be aware that websites from other countries may have information that differs from New Zealand recommendations.

Measuring your blood pressure at home Heart Foundation, Australia, 2016
Blood pressure monitor buying guide Choice, Australia, 2018
BP monitors British and Irish Hypertension Society 

References

1. Cardiovascular disease risk assessment in primary care – managing blood pressure BPAC, NZ, 2018
2. Cardiovascular disease risk assessment and management for primary care Ministry of Health, NZ, 2018
3. Out-of-clinic blood pressure testing in primary care BPAC, NZ, 2016
4. Measuring your blood pressure at home Heart Foundation, Australia, 2016

Reviewed by

Dr Hari Talreja is a renal physician/hypertension specialist with advanced training from Canada and a master’s degree from Harvard University in the USA. He is one of the very few American Society of Hypertension-certified hypertension specialists in New Zealand. He is the clinical lead for transplantation, hypertension and clinical research at Counties Manukau Health. He also practises at Ormiston Specialists Centre, Flatbush and Gilgit Road Specialist Centre, Epsom.