Blood Pressure Part 2: Accuracy counts

How to measure blood pressure accurately

Take your BP regularly at home and you have a reliable and useful record of a major index of your cardiovascular and dementia risk [1], [2].

• It is the only way to identify correct levels of medication for high BP.
• It controls the anxiety and ‘white coat’ effect that increases BP in the surgery or hospital.
• It allows taking 3 measurements to get a more reliable indicator.

Here are the key messages:

• Get the right device
• Be in the right position when you take it
• Always use the same arm
• Have the correct cuff size
• Rest 5 minutes before and measure 3 times at 1-Minute intervals
• Establish a baseline including your BP lying down
• Measure on the first day of every month and record.

Get the right sort of device

An automated upper arm, digital monitor [left below]

Be in the right position

 as shown in the British Heart Foundation picture [right above]

This means sitting upright with your back against the back of a chair and feet flat on the floor, with your arm resting on a table at the same height as your heart. The cuff should be as shown with the tubing over the brachial artery [You can feel a pulse on the funny bone side of each arm]

Aways take the BP in the same arm

Some people have a difference between arms [see "Get your baseline" below] and you should use the arm that registers highest. If the difference is as much as 10-15 mm tell your doctor.

Have the correct cuff size for your arm size

Too small a cuff increases readings; too large a cuff lowers them [3]. Larger or smaller cuffs for the machine you have are available on Amazon or via online pharmacies.

Rest before you start and take 3 measurements

Sit at the table with your kit ready and a way to record your results. Rest for 5 minutes without focusing on your phone, eg listen to some quiet calming music. Take BP 3 times with a 1 minute interval between. Record the lowest measurement and keep a permanent record with dates.

Establish your baseline

You need to be picking up the highest readings

• Take BP in both arms. Always thereafter use the arm that reads highest.
• For 3 days take your BP morning, noon and nighttime. Noon is usually the peak and if there is a big difference then this is when you should do your regular reading
• For 3 days take your BP lying down as well.

[Individuals who have high BP when lying are at significantly greater risk of life threatening cardiovascular events[4]. Talk to your doctor if this is you.]

Measure monthly and keep a record.

This gives you information to discuss with any. Health professional when needed.

---

[1] National High Blood Pressure Education Program. Blood Pressure and Cardiovascular Risk. National Heart, Lung, and Blood Institute; 2004

[2] Santisteban MM, Iadecola C, Carnevale D. Hypertension, neurovascular dysfunction, and cognitive impairment. Hypertension. 2023;80(1):22-34.

[3] Ishigami J, Charleston J, Miller ER 3rd, Matsushita K, Appel LJ, Brady TM. Effects of cuff size on the accuracy of blood pressure readings: The cuff(SZ) randomized crossover trial. JAMA Intern Med. 2023;183(10):1061-1068

[4] Giao DM, Col H, Larbi Kwapong F, et al. Supine Blood Pressure and Risk of Cardiovascular Disease and Mortality. JAMA Cardiol. Published online January 22, 2025. doi:10.1001/jamacardio.2024.5213