a blood pressure monitor

Visit a doctor’s office for almost anything that ails you and the chances are good you will have your blood pressure measured. That’s because it is an essential diagnostic procedure to detect hypertension, a common condition that puts people at risk of heart and kidney disease.

Considering that millions of people have their blood pressure checked every day, it is surprising that this measurement can be so tricky. Mistakes are far more common than most people realize, and the consequences of inaccuracies can be serious.

Falsely Positive Blood Pressure Readings:

A false positive, that is, a reading higher than the true blood pressure, could lead to unnecessary medication. Drugs can be expensive and may have unpleasant side effects such as dizziness, fatigue, impotence, cough or swollen feet.

Falsely Negative Blood Pressure Readings:

A false negative, a reading lower than the actual blood pressure, could lead to undertreatment. This puts people at risk of heart attacks, strokes or kidney disease.

Blood Pressure Cuff:

What causes such errors? According to experts writing in the Journal of Human Hypertension (July, 1997), a common source of error in measuring blood pressure is using the wrong size cuff. A cuff that is too small for a large arm can result in a blood pressure reading higher than it should be. When was the last time a nurse or doctor actually measured your arm circumference and then selected a blood pressure cuff that was designed for your sized arm? Most of the time you will be measured with the device that is handy.

Too Much Talking Going On:

Another potential problem is talking. Not infrequently a nurse or physician taking blood pressure will strike up a conversation, thinking that it may put the patient at ease. On the contrary, talking during blood pressure measurement can easily raise the reading 10 to 20 points.

When we first heard about this phenomenon we were skeptical. How could seemingly casual conversation affect blood pressure? Research by J.J. Lynch, however, has revealed that when someone talks while having her blood pressure measured can have a profound impact on the outcome. In some cases blood pressure can go far higher than 20 points and could result in a false diagnosis of hypertension.

Arm Position Is Important:

The official position of the American Heart Association is that the “Patient’s arm should be supported at heart level.” If your arm is allowed to hang down lower than heart level the reading is likely to be falsely elevated. If, for some odd reason, your arm is allowed to rest above heart level the reading could be falsely lowered.

You might think this fundamental recommendation from the AHA would always be followed. You would be wrong. It never fails to amaze us that most chairs in exam rooms do not have an arm rest at heart level. Unless the nurse or doctor actually supports your arm at the correct level while measuring your blood pressure, chances are good that your arm will be lower than appropriate and that will falsely elevate the reading.

Another problem that is rarely considered by health professionals is a cold examining room. If you are wearing one of those flimsy little paper gowns, feeling chilly and exposed may increase blood pressure more than 10 points.

White Coat Hypertension:

And speaking of uneasiness, “white coat hypertension” affects up to one patient in five. These are people whose blood pressure skyrockets when the doctor walks into the room. Some people with normal blood pressure may have office readings as high as 180/110.

Many doctors and nurses have a hard time accepting this concept. After all, how could their mere presence cause a patient’s blood pressure to spike? Health professionals like to think of themselves as kind, compassionate healers, not scary threats to a patient’s well being. Nevertheless, many people become very anxious the minute a doctor knocks on the exam room door.

Anyone who is susceptible to this phenomenon should be measuring blood pressure at home. There are affordable, easy-to-use digital machines that allow people to keep a diary of their readings over the course of several weeks or months. This permits the physician to get a broader understanding of their blood pressure in a variety of settings. The home machine should always be checked against the equipment in the doctor’s office to make sure it is accurate.

Anyone who would like additional details about proper blood pressure measurement, white coat hypertension and drugs used to treat high blood pressure may find our Guide to Blood Pressure helpful. It has a detailed list of dos and don’ts of measuring and managing blood pressure.

Here is a link to all our guides. And should you want to know some secrets about common mistakes in treating hypertension, check out our book, Best Choices From The People’s Pharmacy.

Measuring blood pressure is harder than it looks. Getting it right requires good technique and careful monitoring over time. This facilitates the best possible treatment for those who need it and protects others from unnecessary medication.

Share your own experience with blood pressure measurement below and please vote on this article at the top of the page.

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  1. Alice

    Most doctors and nurses don’t even know where the brachial artery on the inside of the arm is either. Most doctors and nurses don’t consider the shape of the arm. There has only been a very few times that either a doctor or nurse has taken a blood pressure measurement that were vary close to mind. I also question about how good their hearing is as well. I started taking my blood pressure about 20 years ago because I didn’t trust the doctor’s readings. I think most doctors and nurses need to take training how to take blood pressure properly.

  2. Debbie
    Houston, TX

    I had my blood pressure checked at an endocrinologist’s office. When the young woman finished I asked her what the reading was. She told me it was 124. I asked her 124 over what? Her reply was it is just 124 that is all!

    I have been in many doctor’s offices that claim my bp normal, which is so far from the truth. I have a great deal of problems with my blood pressure and it hasn’t been normal in at least 20 years. Unfortunately this effects the medical care you get.

    My suggestion is to keep a detailed record of your bp in a notebook and bring it in with you. It is important to show that this isn’t a new event, that this has been ongoing.

  3. Laurel

    I am able to donate blood regularly, and they write down the blood pressure readings for me. I take these readings with me to the doctor’s office as proof that normally my readings are acceptable. The folks at the Red Cross do take the readings with my feet on the floor, arm on a table at nearly heart level, quietly, and with a large enough cuff. I trust their readings. The waiting areas are quiet.

    I do not know if they take drop-ins, but if you have one close and are concerned, it wouldn’t hurt to ask. They certainly have no vested interested in the results.

  4. Grace

    I was diagnosed with high BP 30 years ago and have been on medication ever since. A double mastectomy and removal of all lymph nodes in both arms has resulted in lymphedema in both arms — thus, I cannot have blood pressure (or blood work/infusions, etc.) done on my arms. While one person at our cancer center used to take BP near my calf, my primary care office has pretty much stopped monitoring my BP at all. No matter where I go to my — gastroenterologist, gynecologist, urologist, heart specialists, surgeons, neurologist, endocrinologist etc. — no one has ever heard of not using arms to check for BP, they either skip it altogether or several struggle together to come up with another place to put a cuff……..

  5. LOUIS

    In addition to no talking, I have found that no body movement–head, arms, legs and shifting around will result in a most accurate reading, whether at home or in the doctor’s office.
    differences of 10 to 40 points higher occur.

  6. SH

    My husband has HBP and has this Omron Blood Pressure monitor. Omron HEM-711AC Automatic Blood Pressure Monitor with IntelliSense. Every time he goes to the doctor his blood pressure readings are much lower than what he gets with the machine. Changing the batteries helped some, but the readings were still 15 to 20 points higher with the machine. We bought a regular Sphygmomanometer and a stethoscope and started doing it manually instead and his BP is much lower than any of the measurements the machine was taking. I highly advise anyone with a machine to take your BP manually occasionally to check the accuracy of the unit they are using. Ours was reading so high it was scary at times.

    • Alice

      I stopped using digital sphygmomanometers for the reasons you mentioned. The Main Artery Pressure (MAP) and the Pulse on these digital machines work together to determine the systolic and diastolic. You will find that the pulse that the machine gives is much higher then if you take your pulse manually using your finger and a watch with a second hand, especially if you take your blood pressure in the morning. The differences between the 2 pulse readings can be as little as +/-4 to cause the systolic and diastolic to be way off. I have been using a manual sphygmomanometer ever since I found out how these digital things work and the reason they are off.

  7. carol

    I always take my BP at home for the week prior to my doctor visit and give her the readings. As a registered nurse, I am appalled by what I see when the assistants take BP’s. You are sitting on the end of the exam table with your legs dangling and your arm is hanging down. They also never seem to put the cuff on tight enough to pick up an accurate reading. My brachial pulse is difficult to palpate so the cuff needs to be snug to pick up the pulse. I have had readings of 180/110 with the cuff is not even touching my skin but when the cuff is on snug the reading comes down to 120/80. The assistants also don’t allow for a 10 minute rest period after escorting you to the exam room. I bet over half of people on drugs for hypertension have normal blood pressure,

  8. gw
    So Cal

    This blog should be required reading for every nurse and pa that takes blood pressures on a daily basis. I too, have never had my bp taking correctly at a doctor’s office. The numbers are always much higher than what I get on my home device.
    Also, where is the real science/research that shows taking medication to lower bp does more good than harm? Should treatment be based on your home average or your doctor’s office first reading? It seems that millions of people are being over-prescribed meds based on faulty testing.
    It is really disturbing that such a simple test is so incompetently performed almost universally by medical “professionals.” It makes me worry about whether other medical testing is performed safely and correctly.

  9. Mary

    My blood pressure was always high when I went to the doctor’s office. My doctor, who knew that, took it again before I left the office, and it had invariably gone down considerably. Mary M.

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