How to Measure Blood Pressure Correctly at Home

Why Home Readings Are Useful

Blood pressure changes throughout the day with activity, stress, pain, sleep and medicines. Some people have higher readings in a clinic than at home, while others have the opposite pattern. A series of carefully taken home readings helps a doctor see the usual level, judge whether treatment is working, and notice changes early.

Home readings are only helpful if they are taken the same way each time. A handful of accurate readings is more valuable than many readings taken hurriedly or in different positions.

Choosing a Device

An automatic upper-arm monitor is generally preferred for home use. Wrist and finger devices are more sensitive to hand position and are more likely to give inaccurate readings, although a doctor may occasionally advise a wrist device when an upper-arm cuff cannot be used.

Where possible, choose a device that has been clinically validated for accuracy. The packaging or manufacturer information usually states whether a model has passed a recognised validation protocol. If you are unsure, bring the device to your next appointment so that its readings can be compared with a clinic measurement.

Cuff Size Matters

A cuff that is too small for the arm tends to over-read, and a cuff that is too large tends to under-read. Most cuffs have a marked range showing the arm circumference they fit. Measure around the middle of the upper arm and check that it falls within that range. People with larger or very thin arms may need a different cuff size.

Before Taking a Reading

• Avoid caffeine, smoking and exercise for about 30 minutes beforehand.
• Empty the bladder if needed — a full bladder can raise the reading.
• Sit quietly for about five minutes before measuring. Do not talk, use a phone or watch something distressing during this time or during the measurement.
• Remove tight clothing from the upper arm. Do not roll a thick sleeve up so that it squeezes the arm above the cuff.

Step by Step: Taking the Measurement

1. Sit correctly. Use a chair with a back support. Keep both feet flat on the floor and legs uncrossed.
2. Support the arm. Rest the arm on a table so that the cuff is at about the level of the heart. An arm hanging down or held up unsupported will change the reading.
3. Position the cuff. Wrap it on bare skin, snugly but not tightly, with the lower edge about two finger-widths above the elbow crease and the marker over the artery as shown in the device instructions.
4. Stay still and quiet. Press start and remain relaxed and silent until the reading is complete.
5. Repeat. Wait about one minute and take a second reading. If the two readings are very different, a third reading may help.
6. Record immediately. Write down both readings, the pulse if shown, the date and time, and which arm was used.

When and How Often to Measure

Your doctor may give you a specific schedule. A common approach when a doctor wants to assess blood pressure is to take readings in the morning and in the evening over several days, for example before breakfast and before taking morning medicines, and again in the evening. Measuring at similar times each day makes readings easier to compare.

Once blood pressure is stable, measuring very frequently is not usually necessary and can cause unnecessary worry. Checking repeatedly after an unusual reading often produces confusing results; it is better to follow the agreed schedule and discuss concerns with the doctor.

Using One Arm or Both

At a first assessment, a doctor may check both arms, because a consistent difference between arms can be relevant. For home monitoring, use the arm your doctor recommends — usually the one that gives the higher readings — and use the same arm each time.

Common Errors That Affect Readings

• Measuring immediately after walking, climbing stairs, eating a large meal or drinking tea or coffee.
• Sitting on a bed or sofa without back support, or with legs crossed.
• The arm hanging by the side instead of being supported at heart level.
• Using the wrong cuff size or placing the cuff over clothing.
• Talking during the measurement.
• Recording only the "best" reading, or rounding numbers from memory later.

Keeping a Useful Record

A simple written log or a device memory that can be shown to the doctor is ideal. Record every reading taken as part of the schedule, not only unusual ones. Note anything that might explain a reading, such as pain, poor sleep, a missed dose of medicine or feeling unwell. Bring the log and, if possible, the device itself to appointments or to a doctor home visit.

The meaning of a set of readings depends on the individual — their age, other conditions, medicines and the targets their doctor has set. For that reason this guide does not give target numbers. Ask your doctor what range is appropriate for you and at what level you should contact them.

When to Seek Medical Help

Contact your doctor if readings are consistently different from the range your doctor has advised, or if you feel dizzy or faint, particularly when standing up after a change in medicines.

Related Guides

• How to Check Blood Sugar at Home and Avoid Common Errors
• Pulse Oximeter at Home: How to Use It and Understand the Reading
• What Medical Records and Medicines Should You Keep Ready for a Home Visit?
• When Home Care Is Not Enough: Signs You Should Go to Hospital