Causes Of False Blood Pressure Readings

causes of false blood pressure readings

Besides taking your pulse, blood pressure is probably the 2nd most common measurement taken. Unfortunately, many people don’t know the proper way to measure it. This is causing many false blood pressure readings which can negatively affect your blood pressure goals.

What are causes of false blood pressure readings? The following are causes of false blood pressure readings:

  • Incorrect cuff size
  • A cuff that is too tight or loose
  • Incorrect cuff location on the arm
  • Incorrect cuff height
  • Wrapping the cuff around clothing
  • Wrong body position.
  • Failure to take multiple readings
  • Using an inaccurate home monitor

Many of you may be thinking I left some things off the list. One such example may be drinking caffeine right before measuring your blood pressure. While doing that is a mistake you should avoid, in realty it isn’t giving you a false reading. It’s giving you an accurate reading at that moment in time, but doesn’t accurately reflect your normal blood pressure throughout the day. I will also list those mistakes later in this article. But first, here are the errors that can give you false blood pressure readings (resource).

If you don’t have your own home blood pressure monitor yet or you’re thinking about replacing your current one, check out the blood pressure monitor I recommend on Amazon right here. I also wrote a blog post that recommends two other options for you in different price ranges. Check it out by clicking here.

Causes Of False Blood Pressure Readings

Incorrect Cuff Size

Typically, there is a size range on the cuff. My cuff size has a range from 8.75″ to 16.5″. It is essential you measure your upper arm and determine its size. The best way is to take a cloth measuring tape and wrap it around your upper arm. Keep your arm relaxed, as it would be when you will be taking your blood pressure. Once you determine how many inches the circumference of your upper arm is, make sure it’s within the range of your cuff.

If your cuff is too small, there’s a good chance it will be wrapped too tight around your arm making the BP reading falsely higher. If it’s too large, odds are it may be too loose which can give a false reading lower than what your pressure actually is.

Cuff Is Too Tight Or Loose

Even if you have the right size cuff for your arm, it’s still possible to have it too tight or loose. After the cuff is positioned properly on your upper arm, the cuff should be tightened enough so you can insert just 2 fingers between the cuff and your arm. It shouldn’t be too tight where you can’t insert any fingers or too loose where you can move the cuff around your arm.

A cuff that is too tight or loose will give a false reading. Typically, too tight will give you a higher reading and too loose will give you a lower reading.

Incorrect Cuff Location On The Arm

Having the correct cuff size and tightness as indicted above is not a guarantee you still won’t get a false reading. The positioning of the cuff on the arm is just as important. There are 2 things to consider with cuff location. The 1st one is how far away the edge of the cuff should be from the bend of the arm. There is no one right answer for this distance. Each blood pressure monitor will have a different recommended distance. My Welch Allyn 1700 Series recommends a distance of 0.8″ to 1.2″, while the Omron 10 Series recommends a distance of 1/2″.

The 2nd thing to consider with cuff location is the alignment of your cuff. The cuff usually has a marking on it informing you what part of the cuff should be lined up with the inside of your arm. The marking will sometimes have an alignment marker you line up with your arm artery. In addition, the tube is usually lined up with the middle of your inner arm as shown in the photo below.

home blood pressure monitor cuff
My arm cuff.

Incorrect Cuff Height

Cuff height is the level of the cuff compared to mid-heart level. To avoid a false blood pressure reading, the cuff must be at the same height as your heart. If the cuff is above heart level, the reading will be false and lower than your actual pressure. If the cuff is below heart level, the reading will be false and higher than your actual pressure.

This is the most common mistake people make with a wrist monitor. They keep their arm in the same position as they would if they were using an upper arm cuff. By doing this, the cuff and wrist are below heart level. For every inch above or below the heart, your blood pressure reading can be off approximately 2 mm HG.

Wrapping The Cuff Around Clothing

When taking your blood pressure, the cuff should always be wrapped around bare skin and not over any clothing. It doesn’t matter how thin your sleeve may be, it needs to be rolled up, or the shirt must be removed. Research has shown that systolic Bp, when making this error, may be impacted by as much as 10 to 50 mm hg! (resource)

Wrong Body Position

The ideal body position is sitting down with your back supported in an upright position. If this is not possible, the cuff should be at heart level with the arm next to the body. If you must take your blood pressure in another position, like lying down, always give yourself a few minutes of relaxation time after moving into that position (resource).

Failure To Take Multiple Readings

The American College of Cardiology recommends taking 2 to 3 blood pressure measurements and then averaging them together. This method minimizes random error, eliminates one false reading and gives you a more accurate basis for your pressure. Some home monitors, like the one I recommend, will automatically average the last 3 readings for you.

Using An Inaccurate Home Monitor

There’s nothing worse than doing the right thing by checking your BP at home and you’re getting false readings because your monitor is not accurate. This can create a whole bunch of problems like a wrong diagnosis or not knowing for sure if your treatments are working properly.

Whenever you buy a new home monitor, you should take it with you to your next doctor visit. The nurse can check the reading and compare it to their measurement. If for some reason, it’s not accurate, you can return it immediately and get a replacement. Every year, bring your monitor in and have it checked to make sure it remains accurate.

Other Causes Of False Blood Pressure Readings (Mistakes)

The following are things you may be doing that will raise or lower your blood pressure temporarily. At the exact moment of measurement, your blood pressure will probably be different than what it is the rest of the day. This will give you a false indication of your blood pressure, even though it was accurate at the time of measurement (resource).

  • Don’t exercise, drink caffeine or smoke within 30 minutes of taking your blood pressure.
  • If you feel like you have to urinate or do a number two, go to the bathroom prior to measuring your BP. Anything that may stress your body or mind may raise your pressure.
  • Don’t talk while taking your blood pressure. I knew someone who would use their home monitor while talking on the phone. This can definitely change your BP, especially if the conversation is stressful.
  • Make sure the 5 minutes prior to taking your measurement are restful and quiet.
  • This is more of a tip than a mistake. At the initial Bp measurement, take readings in both arms. It’s normal to have a slight difference between the two arms. The arm with the higher measurement should be used for all subsequent readings (resource).

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If you found this Blood Pressure topic interesting check out these related blood pressure articles also found in this same website:

Kevin Garce

Kevin Garce is a Certified Health Coach who encourages people by informing them on blood pressure topics important to them. His years of research and knowledge inspire people to achieve their goals. Read more here About Me

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