How to obtain accurate blood pressure readings

Pharmacist Gurvinder Najran offers advice on how to measure blood pressure (BP) correctly to help support effective hypertension case-finding and long-term condition management

Measuring BP correctly to obtain accurate readings is crucial for effective diagnosis and ongoing management of hypertension and other conditions.

Many community pharmacies offer BP measurement, including as part of the NHS England hypertension case-finding service. This can help to educate people about the risks of high BP, improve hypertension diagnosis rates and offer a more personalised approach to support where needed.

Pharmacists working in GP practices also routinely measure BP, to identify hypertension and to monitor BP in patients on antihypertensive medications or other treatments.

Inaccurate BP readings can result in unnecessary appointments and lead to inappropriate medication changes, which may ultimately result in avoidable admissions.

To make sure BP is measured properly, some key areas need to be considered.

Equipment choice

All BP monitors must be fit for use, properly maintained and used correctly.

Make sure BP monitoring devices come from a reliable supplier and are validated for use. The British and Irish Hypertension Society (BIHS) provides a list of validated monitors on its website.

Automatic BP monitors should be recalibrated every 1-2 years, the exact frequency depending on the specific instructions provided with each device.

For people looking to purchase a BP monitor for self-measurement, the British Heart Foundation provides a list of clinically validated and BIHS approved devices.

Preparing patients for clinic BP measurement

Patients should be appropriately rested before having their BP measured in clinic. People who rush to your pharmacy or GP surgery, for example because of work commitments, may have elevated BP readings due to stress. To mitigate this, always advise patients to arrive in good time and ensure they take a moment to relax before having BP readings.

It’s also important to advise patients to avoid any factors that could influence their readings, where possible – such as refraining from smoking, consuming caffeinated beverages, or engaging in exercise for at least 30 minutes prior to having their blood pressure measured. Additionally, having a full bladder may lead to temporary increases in BP, while measuring BP shortly after a meal can result in falsely low readings.

To improve patient preparation for BP monitoring appointments, consider communicating important information via text message before their visit. Most healthcare software systems offer text message templates that can be easily generated and sent to patients prior to their scheduled appointments.

Over-the-counter medications, including nonsteroidal anti-inflammatory drugs (NSAIDs) and decongestants, may also cause an elevation in BP. Always ask about use of any medications and if a patient reports they have recently taken medication that might elevate BP, it may be necessary to arrange another visit to take another BP reading.

Taking BP correctly in clinic

Healthcare professionals need to be trained to measure BP correctly and give clear instructions to patients.

Ensure the clinic has a designated quiet area for taking BP, with a chair offering back support and a stable surface such as a desk for the patient to rest their outstretched arm on.

Consider the following each time you take a BP reading in clinic:

Cuff size

Using the correct cuff size is critical to ensure both comfort and accurate readings. It is essential to have a range of cuff sizes readily available (and non-latex cuffs for those who have an allergy to latex). A standard cuff size is suitable for most patients, but check that the bladder inside the cuff encircles at least 80% of the mid-upper arm being measured. Cuffs that are too small can artificially inflate BP readings, while too large a cuff can lead to falsely low readings, both potentially leading to misdiagnosis and inappropriate management.

Cuff placement

Always place the cuff on the patient’s bare arm, not over any clothing. Ensure the bottom of the cuff is about 2-3cm above the bend of the elbow.

Resting period

Allow the patient to rest for a few minutes after the cuff is placed before taking the measurement. Measuring BP immediately can give a falsely high reading due to the patient tensing up while having the cuff placed; allowing them time to relax will give a more accurate assessment.

Patient position

Ensure the patient is seated in an upright position with legs uncrossed and feet flat on the ground. The arm used for measurement should be supported at heart level. They should not talk, move or cross their legs during measurement, as these actions can increase BP.

What BP measurements should be taken?

When considering a hypertension diagnosis, NICE guidelines recommend the person’s BP should initially be measured in each arm. If the difference between arms is more than 15mmHg, measurements should be repeated. If the between-arm difference remains greater than 15mmHg, subsequent measurements should be performed on the arm with the higher reading.

However, remember to check if patients have been advised to avoid having BP measurement in a particular arm, for example if they have or are at risk of conditions such as lymphoedema.

If a clinic BP measurement is 140/90 mmHg or higher, a second measurement should be taken; and if the second measurement is significantly different to the first, a third. Record the lower of the last two measurements as the clinic BP.

NICE advises that a raised clinic BP (between 140/90 mmHg and 180/120 mmHg) should always be followed up with ambulatory BP monitoring (ABPM) to confirm or refute a diagnosis of hypertension.

ABPM is recommended as it is more accurate than clinic BP. If ABPM is unsuitable or not tolerated, then home BP monitoring (HBPM) can be performed.

In particular, these approaches help to avoid overdiagnosis due to ‘white coat’ hypertension where a person’s BP is elevated in a clinic environment but normal the rest of the time.

How to use and interpret ABPM

NICE guidance advises that at least two measurements per hour are taken during the individual's usual waking hours, typically between 08:00 and 22:00.

The average value of at least 14 measurements during waking hours is taken as the BP reading. The ABPM device will usually automatically generate the average in a report. In community pharmacies, the pharmacist can submit the report directly to the patient’s GP surgery.

Provide patients with details of the ABPM process ahead of their appointment to have the device fitted – via text message, leaflet or email. Such resources are available on the British and Irish Hypertension Society website. Ensure you obtain full consent from the patient to proceed in having the ABPM device fitted.

Patients should be instructed to visit the pharmacy during the early hours of operation to have the ABPM device fitted and to return the same day before closing to have the device removed.

Unlike the previous protocol for 24-hour ABPM, where pharmacies had to wait until the following day for the ABPM device to be returned, this approach increases capacity for ABPM in pharmacies and reduces the number of ABPM devices required, lowering operational costs.

GP surgeries may also adopt this approach, but many currently continue to monitor for 24 hours, with the patient returning the next morning to have the device removed (though only the daytime readings between 08:00 to 22:00 are used).

Fitting the ABPM device should take roughly 20 minutes. Advise patients that the device will be fitted directly on the arm, not over clothing, so to avoid wearing tightly fitted clothing.

It is important to explain how the device works and the rationale for its use to support accurate diagnosis of hypertension. In addition, patients should be advised to place the cuff on the non-dominant arm (unless this is precluded due to high between-arm readings or clinical conditions, as above).

The ABPM device will measure BP every 30 minutes. An alert is sent to the patient just before the reading is taken. Patients should be advised to follow the steps above during measurement – for example, to sit down with their legs uncrossed and arm supported.

The ABPM device must not get wet therefore any activity such as showering or swimming should be avoided during the duration of wearing the ABPM device. Vigorous exercise should also be avoided as this can cause spikes in BP readings. Patients should not drive during the monitoring period, due to the risk of distraction caused by the cuff inflating; patients who are occupational drivers will only be able to have the ABPM device fitted on a non-working day.

Lastly, patients should not remove the ABPM device themselves, as improper removal could pose a risk of harm to the patient and potentially damage the device.

Supporting uptake of ABPM in pharmacies

As outlined above, ABPM is the gold standard for confirming a diagnosis of hypertension, and is necessary to fulfil the service specification criteria in the hypertension case-finding service. However, people can be reluctant to agree to ABPM in the pharmacy due to inconvenience or disliking the prospect of wearing the cuff for so long.

Here are some key points to consider:

Process familiarity

Explain that the ABPM process is the same as would be performed by the GP practice can help alleviate patient concerns. In my PCN, as part of a pilot programme supporting engagement in the case-finding service, we have found patients are more willing to have their ABPM completed at the pharmacy if we explain this.

Patient reassurance

Take time to explain the process fully and address potential concerns can help to reassure patients and give them the confidence to participate.

Explain the advantages of ABPM

Highlight the benefits of ABPM in ensuring a correct diagnosis and avoiding any unnecessary appointments or treatment to help patients understand its importance.

Patient comfort and compliance

Ensure the ABPM device is fitted correctly to make it comfortable and thereby promote compliance during the monitoring period. The small digital monitor can be attached directly to the cuff or to a belt around the waist, depending on the model of ABPM used.

If someone does decline ABPM, make sure to document the reasons when submitting notification of the raised clinic BP to their GP surgery, as this will support the GP team to take action.

Helping patients to obtain accurate HBPM

When instructing patients to perform HBPM, make sure they are competent to do so and receive proper counselling on how to take readings properly. Here are key points to consider:

Patient competence

Assess the patient’s ability to perform HBPM correctly and provide clear instructions as necessary. Make sure they are aware of the need for a quiet area away from noise and distraction, and to be seated at a table or other surface to support their outstretched arm at chest level.

Educational materials

Offer supportive materials, including links to instructional videos from the British Heart Foundation, to guide patients on measuring their BP correctly.

Equipment requirements

Ensure that patients use an approved BP monitor that measures the BP of the upper arm; it is important to advise against using wrist BP monitors or smartwatches, as these provide less accurate readings than upper arm measurements.

Readings should be taken as follows:

Consecutive measurements

For each BP recording, two consecutive measurements should be taken, at least one minute apart.

Recording schedule

BP should be recorded twice daily, ideally in the morning and evening. This should be continued for a minimum of 4 days, and preferably for 7 days.

Discard initial measurements

Discard the measurements taken on the first day of monitoring to allow the patient to become familiar with the equipment and process.

Average remaining measurements

Use the average value of all the remaining measurements to confirm the reading.

Diagnosis of hypertension

NICE advises staging of a hypertension diagnosis as follows (see box).

Next steps in management depend on the Stage of hypertension and individual patient considerations such as age and comorbidities.

For pharmacies participating in the hypertension case-finding service, onward reporting or referral to local GP practices should be followed in line with the service specification.

Any patient with a BP reading above 180/120mmHg will require urgent same-day assessment by their GP, or immediate referral to A&E if they have acute symptoms such as headache or palpitations.

Gurvinder Najran MRPharmS, Dip, I.Presc, PG Cert, Dudley PCN Pharmacist; Black Country ICB Dudley PCN Engagement Lead

How to obtain accurate blood pressure readings

Equipment choice

Preparing patients for clinic BP measurement