Written by Dr Katie Stephens, GP
Dr Katie graduated from the University of Manchester in 2007 (MBChB) and completed her GP training in the West Midlands in 2012 (MRCGP).
Home blood pressure monitors are small, portable, electronic devices that measure blood pressure with the push of a button. They can be the very best way to get the most accurate blood pressure reading for many people. This is because it can be common for someone’s blood pressure to go up when it is checked at a doctor’s office – something known as White Coat Syndrome. Knowing what your blood pressure is like when you are at home usually gives you a better idea of what it is like most of the time.
The preferred way of diagnosing high blood pressure
If your blood pressure is high when you see your doctor, they will probably want to have it checked when you are at home, as there is a good chance it will drop down when you are more relaxed. In fact, when a GP is thinking about diagnosing someone as having hypertension (the medical term for high blood pressure) for the first time, they usually have the patient take lots of home readings first. Diagnosing hypertension is important, as it can cause strokes, heart attacks, kidney disease and more, and it can be effectively treated with medication and lifestyle changes.
Sometimes these home readings are done with a machine called an ABPM: Ambulatory Blood Pressure Monitoring device. This is a special type of machine that is borrowed from the GP practice and is worn for a full day. It inflates every 30 minutes or so, the readings are stored, and averages are calculated at the end.
If an ABPM isn’t available, or the user isn’t able to tolerate it, national guidelines advise doing something called Home Blood Pressure Monitoring. This is when a home blood pressure monitor is used to check blood pressure in the following way:
- Every day for at least four days, but ideally seven days total
- Twice daily (morning and evening)
- Two readings recorded at each sitting, with at least a minute sitting quietly in between
- At the end of the period, the readings from the first day are discarded and the rest used to work out an average systolic (top number) and diastolic (bottom number) blood pressure.
The device used may be borrowed from the practice, or could be your own private automatic blood pressure machine. If it is a practice machine, these are usually calibrated regularly so anyone using it knows it can be trusted.
Many people decide to use their own personal machine for Home Blood Pressure Monitoring. This is absolutely a valid and often convenient option, but it is best to check that the following two points apply to your machine before using it, as otherwise the readings may be less reliable:
- The machine should be listed on the British and Irish Hypertension Society’s list of approved monitors for home use.
- The machine should not be too old. NHS machines typically get recalibrated every 12 months. Your own machine may stay accurate for up to two years – check your manufacturer’s information to see how long they recommend you can rely on it for. Kinetik Wellbeing has options for helping with blood pressure monitor calibration. For this reason, inexpensive machines may be the best option for many.
Is there anyone who shouldn’t use a home blood pressure monitor?
Generally, a home blood pressure monitor is best for most people. However, if you have atrial fibrillation or other types of irregular heartbeat, these machines may be less accurate for you. The best way to get your blood pressure checked if your heartbeat is irregular is with a manual blood pressure machine. This is when the upper arm cuff is pumped up by hand while someone listens to your pulse on your arm with a stethoscope.
All of Kinetik Wellbeing’s blood pressure monitors come with an irregular heartbeat detection function. For people who may have an irregular heartbeat but don’t know about it, this feature can alert them to the need to get checked over. For more information, please visit our irregular heartbeat blog or read the NHS advice on abnormal heart rhythms.
Tips for Choosing an Accurate Monitor
Clinical validation
You may see some blood pressure machines advertised as being ‘clinically validated’. This means that the device has been tested and proven to meet certain accuracy standards. However, not all standards are equal! Some are easier to meet than others.
Two of the best standards that are used in the UK are from the BIHS (British and Irish Hypertension Society) and the ESH (European Society of Hypertension). In fact, national guidelines in the UK recommend that doctors refer to the BIHS’s approved list of blood pressure monitoring devices – these are devices that have met the standards from the BIHS. If you are interested, the BIHS also has a list of devices they specifically do not recommend as well. (Although, if a machine isn’t on their approved list, it’s safe to say that it is not recommended.)
Cuff Size
After checking that your machine has the right clinical validation, isn’t too old, and seeing your doctor if your pulse is irregular, the next most important factor in getting an accurate reading is checking that you have the correct cuff size. A cuff that is too small will give a reading that is actually higher than the true value. So, it might look like you have high blood pressure when you don’t. A cuff that is too large will give a reading that is too low – making your blood pressure look lower than it is.
The cuffs included with Kinetik Wellbeing’s upper arm blood pressure machines have a circumference of 22-42cm. This means they can be used for most adults and are suitable for both a ‘standard adult’ arm size as well as ‘large adult’ size.
If you would like to check that you have the correct cuff size, you can do this by first finding the midpoint of your arm (halfway between your shoulder and your elbow) and measuring the circumference here. If your arm circumference is larger than 50cm, you may require an extra-large cuff.
Upper Arm vs. Wrist
Wrist monitors are blood pressure machines that are worn on the wrist instead of the upper arm. They may be more convenient for some users, and in fact, some wrist machines are also validated by the BIHS and ESH. However, generally, machines with an upper arm cuff tend to be more accurate than those that wrap around the wrist, and are preferred by doctors.
Extra Tech
Even once you have an accurate, in-date machine with the correct cuff size, sometimes it is still possible to make errors when checking your blood pressure at home. Two of Kinetik Wellbeing machines (the TMB-2080 and TMB-2088) have some extra bits of tech to help alert you to potential user errors:
- Body Movement Detection
- Cuff Wrap Detection
- Irregular heartbeat detection
Tips for Avoiding User Errors
User errors happen when instructions for measuring your blood pressure aren’t followed closely. In my work, I almost always notice higher readings if the user isn’t able to stay quiet and still while the cuff inflates and then deflates fully. Follow these tips to boost the accuracy of your home blood pressure readings:
- Avoid caffeine, cigarettes and exercise for at least 30min prior to checking your blood pressure.
- Sit quietly for at least a minute (but up to 5 minutes) before taking a reading
- Remove any thick clothing, rather than rolling sleeves up; the cuff should sit either directly on the skin or only over very thin sleeves.
- You arm should be resting on a surface with the cuff at the level of your heart
- Your chair should have a back that you can lean against
- Both feet should be flat on the ground with legs uncrossed
- Stay still and don’t speak while the machine is taking the reading
For even more accuracy, stay still and quiet for a full minute afterwards and repeat the reading. If the second reading is similar to the first, then they are both likely to be accurate. If it is much lower, (and there is no ‘irregular heartbeat’ alert showing), then the second reading is likely to be the more accurate one. If this happens, stay still and quiet for another minute and repeat the reading again. When you have two readings that are similar, you have most likely found your accurate blood pressure.
FAQs about blood pressure monitor accuracy
Are digital blood pressure monitors accurate?
It depends on the monitor and it’s age, but essentially yes, they can not only be accurate, but may potentially be even more reliable than readings done at a doctor’s office. Click in order to see Kinetik Wellbeing’s blood pressure monitors for home.
Are manual blood pressure monitors more accurate than digital?
For people who have an irregular heartbeat, such as atrial fibrillation, manual blood pressure monitors are generally more accurate than digital machines.
Are wrist blood pressure monitors accurate?
Usually, wrist blood pressure monitors are not as accurate as machines with a cuff that is worn on the upper arm. However, there are some wrist blood pressure monitors that are validated by the BIHS and ESH and so do give reasonably reliable readings.
Which is better: wrist or cuff blood pressure monitors?
For most users, the cuff blood pressure monitor (where the cuff is worn on the upper arm) is the better choice. However, for some individuals, the wrist monitor may be preferable, for instance, if it is not possible to get a cuff that is large enough for your arm.