Correct measurement and interpretation of a person’s blood pressure (BP) is essential in the diagnosis and management of high blood pressure (hypertension). It is important that the BP machine being used is accurate, the proper cuff size is selected, and the patient is positioned correctly. Blood pressure can be measured using one of the following three ways:

(1) Home BP monitoring

Basic home blood pressure monitoring

If the BP is measured at home to establish a new diagnosis of hypertension or to assess BP control, about 12 measurements should be obtained with both morning and evening measurements taken, over a one-week period. Home monitors should be checked for accuracy, initially and then at least annually, in the doctor's office. Patients or their caregivers should be able to demonstrate the proper technique of BP measurement. When using home monitoring in very overweight patients, wrist cuffs may be used if appropriately large arm cuffs are unavailable. Patients being managed for previously diagnosed hypertension should continue to monitor their BP at home. If home BP cannot be monitored, management of the patient can be done with clinic measurements.

Buying your home blood pressure monitor

Home BP monitors are sold in many stores and online. Product-rating sources such as Consumer Reports can help you decide which specific monitor from which manufacturer is good for you. Examples of manufacturers include:

• A&D Medical
  • A&D Medical Deluxe Connected UA-651BLE
  • A&D Medical UA767F (CNET best monitor for multiple users)
  • A&D Medical UA-611
  • A&D Medical UA1030T with Talking Function (Verywell Health best talking-feature monitor)
  • A&D Medical UB-1100 – for wrist

• Equate (Walmart)
  • Equate (Walmart) 4000 series
  • Equate (Walmart) 4500 Series bp3kc1-3ewm – for wrist

•  iHealth
  • iHealth Clear BPM1
  • iHealth Track KN550BT (CNET & Healthline best budget monitor)
  • iHealth Wireless BP5
  • iHealth View BP7s – for wrist
  • iHealth Wireless BP7 – for wrist

• LifeSource
  • LifeSource UA-787EJ
  • LifeSource with Extra-Large Cuff UA-789AC (CNET & Healthline best monitor for large arms)

•  Omron
  • Omron 10 Series BP7450
  • Omron 3 Series BP7100 (Verywell Health best budget monitor)
  • Omron 5 Series BP7250 (Verywell Health best monitor with an app)
  • Omron Evolv BP7000 (Healthline best monitor for multiple users) (Verywell Health best one-piece monitor)
  • Omron Platinum BP5450 (Amazon) (Verywell Health best data-display in a monitor)
  • Omron Gold BP5350 (Amazon) (Verywell Health best overall monitor)
  • Omron Silver BP5250 (Amazon)
  • Omron 3 Series BP6100 – for wrist
  • Omron 7 Series BP6350 – for wrist
  • Omron Gold BP4350 (Amazon) – for wrist (CNET & Healthline best wrist monitor)
  • Omron Healthcare Heart Guide BP8000-M – for wrist

• Qardio
  • Qardio QardioArm (CNET best overall monitor)

•  Rite Aid
  • Rite Aid Deluxe Automatic BP3AR1-4DRITE

• Withings
  • Withings BPM Connect (CNET best runner-up monitor) (Healthline best overall monitor)

(2) Ambulatory BP monitoring (ABPM)

Ambulatory blood pressure monitoring

Ambulatory blood pressure monitoring (ABPM) uses a device worn by the patient and takes multiple blood pressure measurements over a 1-2 day period. When ABPM is used, hypertension is defined as a 24-hour average BP greater than or equal to 125/75 mmHg, average daytime BP greater than or equal to 130/80 mmHg, or average nighttime BP greater than or equal to 110/65 mmHg. ABPM is recommended as the reference standard for diagnosing hypertension and is a better predictor of future cardiovascular bad events compared with using typical office-based BP measurements. Home BP monitoring is acceptable as an alternative to ABPM, because ABPM is not available in most clinicians' offices due to a combination of factors, such as ABPM’s higher cost and low reimbursement by insurers.

(3) Office or clinic BP monitoring

Office-based blood pressure measurements

Screening for hypertension is still typically performed in the doctor's office. Although such office measurements are recommended to find which patients might have hypertension, some people will not have hypertension upon further testing (they might have “white coat” hypertension). Twenty to 30 percent of patients with high BP measurements in the clinician's office have normal BP outside of the office. This is called "white coat" hypertension as it is due to patients feeling anxious in medical offices.

In general, non-office measurements obtained by ABPM and home BP monitoring are lower than those obtained by standard office measurements by approximately 5 to 10 mmHg. Interestingly, office readings obtained using an automated device in which multiple BP measurements are automatically obtained with the patient alone, unattended in a room, more closely approximate ABPM and home BP readings than standard office measurements. Thus, an unattended automated device may be preferred in clinical settings in order to prevent the white coat effect during BP measurement.

Proper measurement of blood pressure requires attention to several things:

• When should I measure BP?
• What size cuff to use?
• How should I do the measurement?
• How many times do I check BP?
• Can I use a wrist monitor?

When should I measure BP?

Blood pressure is variable throughout the day. Daytime BP, which is usually when patients are evaluated in a clinic, can change from hour to hour and is affected by mental and physical activity, emotional stress, and what time antihypertensive medications were taken. For clinic monitoring of antihypertensive therapy, the BP should ideally be measured at approximately the same time of day at each visit, before medications are taken that day.

Other things that can influence the BP should be avoided in the 30 minutes prior to measuring BP. These activities include eating food, exercising vigorously, smoking, and ingesting caffeine. Smoking transiently raises the BP. Caffeine intake can raise the BP. Even measuring the BP in a cold room (54°F) or while the patient is talking can raise the measurement by as much as 8 to 15 mmHg. 

What size cuff to use?

Using a proper size cuff is essential. If too small a cuff is used, the pressure in the cuff may be much higher than the arterial pressure in the arm, which can lead to overestimation of the systolic blood pressure. Recommended cuff sizes for the following arm circumferences are:

• Arm size 22 to 26 cm: use a SMALL adult cuff (12 x 22 cm)
• Arm size 27 to 34 cm: use a REGULAR adult cuff (16 x 30 cm)
• Arm size 35 to 44 cm: use a LARGE adult cuff (16 x 36 cm)
• Arm size 45 to 52 cm: use an adult THIGH cuff (16 x 42 cm)

How should I do the measurement?

Position — The BP should be taken with the person seated, with the back supported and legs uncrossed. Otherwise, the diastolic pressure may be higher by 6 mmHg if the back is unsupported, and the systolic pressure may be raised by 5 to 8 mmHg if the legs are crossed.

The arm should be supported (resting) at the level of the heart. If the arm is allowed to hang down unsupported, the measured BP may be elevated by 10 to 12 mmHg due to gravity. The patient should sit quietly for five minutes before measuring the BP. Having a full bladder, talking, or noise can also increase the blood pressure reading. 

Cuff placement — The BP cuff should be placed on the bare arm or over a thin shirt sleeve. The person's sleeve should not be rolled up nor should the measurement be taken over a thick sleeve, as this may lead to an overestimate of the BP. The lower end of the BP cuff should be 1 inch above the elbow crease.

Measuring technique — Once the cuff is adequately placed, the person should not talk during the measurement. The BP should be taken with the arm supported (resting) at the level of the heart.

Blood pressure should be measured initially in both arms for a new patient. If there is a big difference in the readings, the arm with higher pressure should be chosen. The BP should be taken twice in the chosen arm during each measuring episode, with the measurements separated by one to two minutes. The recorded value on the patient's chart or home BP diary should be the average of the two measurements.

How many times do I check BP?

If the BP is measured at home to diagnose hypertension or to assess BP control, at least 12 measurements should be recorded, with both morning and evening measurements taken over one week.

If measurements are done at a clinic, studies show that the BP drops by an average of 10 to 15 mmHg between the first and third visits in newly diagnosed patients. Thus, many patients with a high measurement at their initial visit turn out to be normal. The diagnosis of hypertension should not be made in an otherwise well patient until the BP has been measured on at least three visits.

Can I use a wrist monitor?

Measurement of BP at the wrist (radial artery) may be necessary in overweight or obese people (when an extra-large cuff cannot be obtained, such as with many home blood pressure monitors) and in patients with breast cancer who had armpit lymph node surgery. However, BP measurement at the wrist should not be used routinely if upper arm measurement is available. At the wrist, the extra pressure due to the lower position of the wrist relative to the heart can result in a false elevation of BP. This can be avoided by taking the wrist BP with the wrist resting at the level of the heart.

There are occasional patients in whom the BP needs to be measured in the legs, such as patients who have a narrowed aorta or who cannot have BP measured in the arms due to surgery, indwelling catheters, vascular fistulae, or grafts. As with measurements in an arm, leg measurements also need an appropriately sized cuff.