A practical guide to accurate home blood pressure measurement

We get our blood pressure checked each time we visit our doctor’s office. However, the numbers may not always accurately reflect our baseline blood pressure due to the reasons I will discuss below.  It is beneficial to monitor our blood pressure at home when we are relaxed in a familiar environment.  And here is a short note on why and how.

What is considered high blood pressure?

According to the latest guideline by American College of Cardiology/American Heart Association (ACC/AHA), blood pressure <120/80 mmHg is normal. Elevated blood pressure is defined as 120-129/<80 mmHg. Hypertension (high blood pressure) is diagnosed if your systolic pressure >130 mmHg OR diastolic pressure >80 mmHg.   To understand the meaning of the two numbers in a blood pressure reading, see my detailed explanation in this article.

Importance of home blood pressure monitoring

Some people’s blood pressure goes up each time they are in the doctor’s office.  This is called “white-coat hypertension”, constituting 10-20% of high blood pressure seen in a clinician’s office 1,2.  Some people are nervous when they see a doctor or a nurse in the office.  Some others tell me that they don’t feel nervous at all, yet their blood pressure I get at the clinic is still higher than what they see at home.  Even if we are not “afraid of” the white coat, often we visit our doctor in the middle of a busy workday and after a cup of coffee. Therefore we don’t have enough time to rest before we get called into the room by the nurse. 

For these reasons, having a record of accurate blood pressure readings from home would help us obtain a more realistic evaluation of our health condition from the doctor, and avoid unnecessary stress or event treatment.

Choose a monitor

Basic home blood pressure monitors cost around $30~50 and can be purchased at any pharmacy.  Although I have not done a thorough side-by-side comparison of which monitors are better, the ones I have used all seem quite reliable.  Monitors with an upper arm cuff works better than those with a wrist cuff.  However, if a wrist-cuff monitor is the only thing you have, it still can be used.  When using it, make sure you place your wrist at the heart level, instead of on the table or hanging down.

Simple tips to an accurate reading

First, get ready.  Rest for at least 5 minutes if you have been walking around.  Avoid smoking, caffeine, stress and vigorous exercises right before you take the measurement. 

I came up with this mnemonic to help us remember the most essential tips: LEFT ABS. It sounds silly but it works.

L – Legs uncrossed

E – Empty your bladder

F – Feet both on the ground

T – Talk later (be quiet)

A – Arm exposed and supported at heart level

B – Back supported

S – Size of cuff correct

According to American Medical Association, not following the above steps could cause your blood pressure elevated by 2~50 mmHg. Thus it is worthwhile going through the above checklist when you take your measurement.

Keep a log of your home blood pressure readings

A paper journal works well.  If you use smart phones, there are very handy apps that help you keep a neat record on your phone.  Write down the date and time of the day when you take the measurement, medications you take, and your diet on that day.  Your exercises and stress levels can be helpful information too. Next, always remember to bring your log and show it to your doctor during your visit.

Bring your own monitor to your next doctor visit

Sometimes when I asked my patients whether they monitor their blood pressure at home, I was told: “I used to, but the numbers are so random that I don’t think my monitor is still working”.  It is quite disappointing and a waste of money if we have a monitor at home but we don’t trust it enough to use it.  The easiest fix to this issue is to bring your monitor to your doctor’s office.  After the nurse or doctor take your blood pressure, you take a measurement using your own monitor and compare the readings.  This step will allow you to calibrate your monitor.  Moreover, when your doctor watches how you measure your blood pressure, you will get suggestions on whether you have been doing it correctly.  During my medical training, I have done this often for patients at the clinic. I always appreciate that I have a chance to help them get accurate measurement of blood pressure at home, so that we could better evaluate their condition and adjust medication if necessary.

References

1.           Mancia G, Bombelli M, Brambilla G, et al. Long-term prognostic value of white coat hypertension: an insight from diagnostic use of both ambulatory and home blood pressure measurements. Hypertension 2013;62(1):168–74.

2.           Pickering TG, James GD, Boddie C, Harshfield GA, Blank S, Laragh JH. How common is white coat hypertension? JAMA 1988;259(2):225–8.

About the Author Isabel Wang, MD/PhD

I received my MD from PUMC in Beijing China and my Ph.D. in Biochemistry from Stony Brook University on Long Island. Over the years, I have worked in the fields of genetic research and clinical medicine in different parts of the US, including PA, MO, CT, FL, NY and MI. My research has been published in multiple scientific journals. Currently I live in Ann Arbor, MI with my husband and our children and Mango the orange tabby. I love hiking, running, baking, cooking and biking.

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