Home Blood Pressure Monitoring:
How to Measure Accurately and What Your Numbers Mean

A single blood pressure reading at the clinic can be misleading. Some people's blood pressure rises only in the clinic ("white-coat hypertension"), while others have normal clinic readings but high blood pressure the rest of the time ("masked hypertension"). In registry studies, up to one in three people in each situation was misclassified by clinic readings alone. Measuring at home, with a validated upper-arm monitor over several days, gives a truer picture and is now recommended by guidelines for diagnosing and managing high blood pressure. A home average of about 135/85 mmHg corresponds to a clinic reading of 140/90. Home monitoring also helps treatment: in an analysis of 25 trials, self-monitoring lowered systolic blood pressure by 3.2 mmHg overall, and by 6.1 mmHg when combined with support such as medicine adjustments and education. This guide explains how to choose a monitor, measure correctly and make sense of your readings.

Key numbers

Why measure at home?

Blood pressure varies throughout the day, and clinic readings capture only a moment, often when you're anxious or rushed. Home readings, averaged over several days, better reflect your usual blood pressure and are more closely linked to future heart and kidney problems. They help to:

• Confirm a diagnosis before starting treatment, and avoid unnecessary medicine for white-coat hypertension.
• Detect masked hypertension, which carries a similar cardiovascular risk to sustained high blood pressure.
• Check whether lifestyle changes or medicines are working (see Lowering Blood Pressure Without Medication).
• Keep you engaged in managing your own health.

Choosing a monitor

• Use an upper-arm cuff monitor. Wrist monitors and smartwatches are more affected by arm position and are generally less accurate.
• Choose a validated device. Check an independent validation list, such as the US Validated Device Listing (validatebp.org) or STRIDE BP.
• Get the right cuff size. The inflatable part should cover 75-100% of the distance around your upper arm. A cuff that's too small gives falsely high readings.
• Check it against a clinic reading when you first buy it, and every year or two.

How to measure correctly

Small errors can shift readings by 5-10 mmHg or more (see Blood Pressure Explained). Each time:

• 1. Avoid caffeine, exercise and smoking for 30 minutes beforehand, and empty your bladder.
• 2. Sit quietly for 5 minutes, back supported, feet flat on the floor, legs uncrossed.
• 3. Rest your arm on a table with the cuff at heart level, on bare skin.
• 4. Don't talk or use your phone during the measurement.
• 5. Take two readings, one minute apart, and record both.

The home monitoring protocol

For diagnosis, or after a change in treatment:

• Measure twice a day: in the morning, before medicines and breakfast, and in the evening.
• Take two readings each time, one minute apart.
• Continue for at least 3 days, ideally 7. Many guidelines suggest ignoring the first day's readings, which tend to be higher.
• Average all the readings and share them with your doctor.

For long-term monitoring once blood pressure is controlled, a few readings a week, or a week of readings before a clinic visit, is usually enough.

What your numbers mean

If you're on treatment, your doctor may set a lower personal target. Don't adjust medicines based on a single reading; look at the average over several days.

Does home monitoring improve blood pressure?

A 2017 analysis of individual data from 25 trials found that self-monitoring lowered clinic systolic blood pressure by 3.2 mmHg at 12 months compared with usual care. But the effect depended on what was done with the readings: monitoring alone made no significant difference (1.0 mmHg), whereas combining it with support, such as medicine adjustments by a doctor or pharmacist, education or lifestyle counselling, lowered systolic pressure by 6.1 mmHg. Readings are only useful if they lead to action.

Recommendations by scenario

Practical notes

Home blood pressure monitoring gives a more accurate picture than clinic readings alone, uncovering white-coat and masked hypertension and showing whether treatment is working. Use a validated upper-arm monitor with the right cuff size, measure correctly, and follow a simple schedule of two readings morning and evening for up to a week. A home average of 135/85 mmHg or higher suggests high blood pressure (see Hypertension and Longevity). Most importantly, share your readings with your doctor, because monitoring helps most when it leads to action.