Home blood pressure monitoring: how to measure it properly

The 2024 guidelines of the European Society of Cardiology (ESC) list among the advantages of home monitoring that it helps identify white coat hypertension, where blood pressure is high in the office and normal at home, and masked hypertension, the reverse. Once a treatment has started, home readings also help follow its effect over time.

Home monitoring sits alongside ambulatory monitoring, a device worn for 24 hours that the NHS describes as fitted at a surgery or hospital and returned the next day. The ESC presents the two as complementary: the ambulatory device can also capture blood pressure during the night.

The ESC guidelines call for a clinically validated monitor, usually an upper-arm oscillometric cuff device. Cuff size matters: an under-sized cuff artificially raises the reading, an over-sized one lowers it. Ask a pharmacist, nurse or doctor to check that the cuff fits your arm.

Monitors age. The ESC advises asking your healthcare provider to check the device’s accuracy from time to time, and notes that devices older than four years may be inaccurate and should then be replaced. Bringing your monitor to an appointment is also a chance to have your technique checked.

A watch or ring that displays a “blood pressure” is not a substitute for a validated cuff monitor: the ESC currently recommends none of these cuffless methods for routine clinical use. What these sensors do measure, and how to read their trends, is covered in our article on health wearables.

The ESC guidelines apply the same preparation at home as in the office. Avoid exercise, caffeine and tobacco for at least 30 minutes beforehand, empty your bladder if needed, then sit comfortably for 5 minutes before the first reading.

Sit with your back supported and your legs uncrossed, feet flat on the floor. Rest your arm on a table, cuff at heart level: an unsupported arm tenses the muscles and raises the reading. Remove clothing where the cuff goes rather than rolling up a sleeve, which can squeeze the arm like a tourniquet. Do not talk during or between readings: France’s national health insurance, Assurance Maladie, notes that talking raises the values by 6 to 7 mmHg.

Always use the same arm. At a first visit, the ESC recommends measuring both arms; if the difference is marked, later readings use the arm with the higher value. Ask your doctor which one to use.

The ESC protocol is two readings per session, 1 to 2 minutes apart, morning and evening at the same times, for at least 3 days and up to 7. If the average after 3 days is close to the threshold, the series continues for the full 7 days. Take morning readings before breakfast and before any medication, but not immediately after waking up. The NHS likewise asks you to wait a minute between readings, and leaves it to your doctor or nurse to say how many days.

In France, the Assurance Maladie presents its own “rule of 3”: three readings in the morning, three in the evening, 1 to 2 minutes apart, for three days in a row, giving 18 readings for the doctor to average. It is the same logic, more readings per session. Whatever protocol you are given, follow it, and keep every reading, not just the lowest.

In your log, write down the date, the time, the systolic pressure, the diastolic pressure and the pulse shown. Add anything unusual: a symptom, a missed dose, a very short night, unusual activity. The ESC asks patients to keep such a record.

With MyTwin for patients, your medical reports, test results and treatments sit in one application, alongside the health devices you connect to it: your readings keep their context from one appointment to the next. Reading them remains your doctor’s job.

As the WHO puts it, the first number, systolic, is the pressure in the blood vessels when the heart contracts; the second, diastolic, is the pressure when the heart rests between beats. Blood pressure varies naturally, so a single high reading does not make a diagnosis, and a single low one does not rule anything out.

For home readings, the ESC guidelines define hypertension as an average of 135/85 mmHg or higher, and the NHS uses the same figure. The ESC also introduced an “elevated blood pressure” category below it, from 120/70 to under 135/85 mmHg at home. France uses the same home threshold: both the Assurance Maladie and the national health authority, HAS, consider a home average below 135/85 mmHg normal.

These thresholds are for diagnosis; treatment targets depend on your age, other conditions, pregnancy and treatment. Do not apply a general threshold as a personal instruction: your doctor looks at the average and at whether the series holds together.

Measuring only when you feel unwell

Every number ends up tied to a symptom and the series is skewed. High blood pressure is usually silent, and a headache has many other causes. A regular protocol tells your doctor more.

Measuring again until you feel reassured

Ten readings in a row raise anxiety and invite you to keep the value you hoped for. Stick to the planned number. If a reading looks technically wrong, note it rather than deleting it.

Changing your treatment on your own

High or low readings can have several explanations. Do not double, skip or stop a dose without instructions: contact your doctor or the service named in your care plan.

Measuring instead of calling for help

A monitor should never delay a call. Chest pain that feels tight or squeezing, a possible sign of a heart attack, or a drooping face, an arm you cannot lift, sudden difficulty speaking, possible signs of a stroke, mean calling your local emergency number straight away (15 or 112 in France, 911 in the US, 999 in the UK), even if the signs go away.

Before the appointment, check that your log has every reading, the dates and the protocol you followed. Bring your monitor if your technique needs checking. Our guide on how to prepare for a doctor’s appointment helps with the rest.

Bring a full list of your medicines too, including those bought without a prescription: the ESC counts drugs and substances that can raise blood pressure among the things to check when it stays high. Keeping that medication list up to date has its own method.

A few questions to ask:

• Is the series technically valid?
• What average do you take from it?
• Should I keep measuring, and how often?
• Which symptoms or numbers should make me call?
• When do we review the treatment?

If your readings are sent remotely to a care team, ask who receives them, how quickly, and what happens if something is off. That is what separates remote patient monitoring from simply sending data.

Home monitoring answers a specific question: confirming a diagnosis, checking whether a treatment works. Measuring several times a day indefinitely is not always useful. Agree with your doctor on when the series starts, when it ends and what it is for. If measuring makes you anxious, say so: the protocol can sometimes be simplified.

A simple table is often enough to keep your readings. Avoid posting screenshots that show your identity or treatments, and if you use an app, check the permissions it asks for and whether you can export your readings.