Home Blood Pressure Monitoring: How to Get It Right Every Time

High blood pressure is called the silent killer because it rarely causes symptoms until it has damaged the heart, brain or kidneys. A single reading in a busy clinic often does not tell the full story. Home blood pressure monitoring gives you and your doctor a more accurate picture, and it shows whether your treatment is working. Here is how to do it properly.

Why measure at home?

Some people’s blood pressure rises in hospital because of anxiety. Doctors call this the white coat effect. Others have normal readings in the clinic but high readings in daily life. Home readings taken over several days capture your true average. Home blood pressure monitoring also involves you directly in your own care, which is one reason doctors now recommend it for most people with hypertension.

In addition, studies show that people who monitor at home tend to take their medicines more consistently and reach their targets sooner.

Who benefits most

Almost anyone with raised blood pressure can gain from measuring at home. It is especially useful for:

• People who have just been diagnosed, to confirm the diagnosis
• Anyone starting or changing medicine
• People with diabetes or kidney disease, who have stricter targets
• Pregnant women advised to do so by their midwife or doctor
• Older adults who feel dizzy and may be over-treated
• People whose clinic readings swing widely

One caution applies. Automatic monitors can be less accurate in people with an irregular heartbeat. If you have this condition, ask your doctor which device to use.

Choosing the right monitor

• Pick an automatic upper arm monitor. Wrist and finger devices are less reliable.
• Ask for a clinically validated model. Your pharmacist can tell you which brands have passed independent accuracy testing.
• Check the cuff size. A cuff that is too small gives a falsely high reading. People with larger arms need a large cuff.
• Compare it once a year. Take your monitor to the clinic and check it against the clinic’s device.

A step-by-step guide to home blood pressure monitoring

• Prepare. Avoid caffeine, smoking and exercise for 30 minutes beforehand, and empty your bladder.

• Sit correctly. Keep your back supported, feet flat on the floor and legs uncrossed. Rest quietly for five minutes.

• Position your arm. Rest your bare arm on a table so that the cuff is level with your heart. Place the lower edge of the cuff about two finger-widths above the bend of the elbow.

• Stay still and silent. Do not talk, laugh or use your phone during the reading.

• Take two readings, one minute apart. Record both.

• Write everything down. Note the date, time, both numbers and your pulse.

Which arm should you use?

The first time you measure, check both arms. A small difference is normal. Afterwards, always use the arm that gave the higher reading, and use the same arm every time. If the difference between arms is more than 15 mmHg on repeated checks, tell your doctor, because it may need investigating.

How often should you check?

When you are starting or changing treatment, measure every morning and evening for seven days. Take the morning reading before your medicines and breakfast. Afterwards, ignore the first day and work out the average of the rest.

Once your blood pressure is stable, a few days of readings each month is enough. Bring your record to every clinic visit, or send a photo of it to your doctor or pharmacist beforehand. However, avoid checking many times a day, because worrying about the numbers can push them up.

Understanding your numbers

The top number is the systolic pressure, and the bottom number is the diastolic pressure. At home, an average of 135/85 mmHg or higher counts as high blood pressure. Your doctor may set a lower personal target, especially if you have diabetes or kidney disease.

One high reading is not a reason to panic. Instead, rest for five minutes and repeat it.

Seek emergency care immediately if your reading is 180/120 or above and you also have chest pain, breathlessness, a severe headache, blurred vision, confusion or weakness. If the reading is that high but you feel well, recheck after five minutes of rest. If it remains high, contact your doctor the same day.

 

What makes readings go up and down

Blood pressure is not a fixed number. It changes from minute to minute, and several everyday factors push it up:

• Pain, stress, anger or anxiety
• A full bladder
• Coffee, cola, energy drinks and cigarettes
• Alcohol and a very salty meal
• Cold weather or a cold room
• Poor sleep
• Missed doses of your medicine
• Cold and catarrh remedies, and painkillers such as ibuprofen

Blood pressure is also naturally lower during sleep and rises in the early morning. Consequently, a single reading tells you little. The average over several days is what counts, and this is the real strength of home blood pressure monitoring.

Low readings matter too

Treatment can sometimes work too well. A reading below 90/60 mmHg, together with dizziness, fainting or blurred vision, should be reported. This is more likely in older adults, in hot weather, during an illness with vomiting or diarrhoea, and when several medicines are combined.

To check, measure while sitting, then stand up and measure again after one minute. If the top number falls by 20 or more and you feel light-headed, tell your doctor. However, do not stop your tablets on your own.

Keeping a record your doctor can use

A clear record is what makes home blood pressure monitoring useful to your doctor. Use a notebook, a printed chart or a phone app, and write down:

• The date and time
• Both readings and your pulse
• Which arm you used
• Anything unusual, such as a missed dose, a headache or a stressful day

Before each appointment, work out your seven-day average or ask your pharmacist to help. Many doctors are happy to receive a photo of the record by WhatsApp ahead of the visit.

Monitoring during pregnancy

High blood pressure in pregnancy can be dangerous for mother and baby. Therefore, pregnant women who are asked to measure at home should use a device that has been validated for pregnancy.

Contact your midwife or doctor the same day if a reading is 140/90 or higher. Go to hospital immediately if it is 160/110 or higher. The same applies if a raised reading comes with a severe headache, blurred vision, pain below the ribs or sudden swelling of the face and hands.

Common mistakes to avoid

• Measuring over clothing
• Using a cuff that is too loose or too tight
• Crossing your legs or letting your arm hang down
• Checking straight after a meal, coffee or an argument
• Changing your dose on your own
• Stopping your medicine because the readings look normal

Remember that the readings are normal because the medicine is working. Therefore, keep taking it unless your doctor advises otherwise.

Frequently asked questions

Are wrist monitors accurate enough?

They are less reliable, because the wrist must be held exactly at heart level. Use one only if an upper arm cuff does not fit.

Can my phone or smartwatch measure blood pressure?

Apps that claim to measure without a cuff are not accurate enough for medical decisions. Use them only to store readings.

Should I measure when I have a headache?

You can, but remember that pain raises blood pressure. A headache is not a reliable sign that your pressure is high.

How long does a monitor last?

A good device lasts several years. Check it against a clinic machine once a year, and replace the cuff if it is cracked or no longer grips.

Can home blood pressure monitoring replace clinic visits?

No. It makes those visits more useful. You still need check-ups for your kidneys, heart, eyes and medicines.

Start this week

Home blood pressure monitoring takes about five minutes, twice a day. Begin with a seven-day record, share it with your doctor or pharmacist and agree on a target. From then on, you will know for certain whether your treatment is doing its job.

Getting help

Home blood pressure monitoring works best when someone reviews the results with you. HubPharm supplies validated monitors, and our pharmacists will show you how to use one and help you share your record with your doctor. For more background, read about common blood pressure medications or the World Health Organization’s hypertension fact sheet.