Ensuring an accurate blood pressure reading

Created date

August 22nd, 2019
Dr. Narrett leads the medical team at all Erickson Living communities. A graduate of Harvard Medical School, he has been providing care for seniors for over three decades.

High blood pressure affects millions of Americans and is the most common reason for a doctor visit nationwide. Every day, treatment decisions and recommendations are made based upon this simple measurement. Because of this, it is essential for the measurement to be accurate. 

While it is relatively easy to check blood pressure (BP) in the office or home setting, it can be remarkably difficult to get an accurate reading. This is because BP can change from one minute to the next based upon everything from caffeine and nicotine intake to when you last exercised. Believe it or not, whether you are speaking or sitting quietly will impact your measurement. 

This variability in measurement is especially important to consider because small changes (as little as 5 mm) can make the difference in diagnosis and treatment. It has been estimated that inaccurate in-office measurements can lead to treatment changes in up to 20% to 45% of cases.

So what can we do to get as accurate a reading as possible? In the medical office setting, you can help by avoiding a big meal, alcohol, caffeine, or tobacco before the visit. Also, give yourself plenty of time to avoid rushing, and you should refrain from exercising right before your visit. Finally, empty your bladder and rest quietly in a chair with legs uncrossed in a comfortable position ideally for at least five minutes before your BP measurement. The medical office staff should do their part as well by using the correct size BP cuff for your arm, keeping your arm at the level of your heart during measurement, and placing the cuff on your bare arm, not over clothing. Finally, two or three measurements should be made if there is a concern, often including readings taken while you are lying down and also standing—this is particularly important among seniors as blood pressure may fall upon standing.

‘White coat effect’

Seems like a lot to consider for such a seemingly simple measurement, but remarkably enough, there is more. The location of measurement and who is taking the reading matters too. At home, your BP may be lower than at the doctor’s office, and research shows us that measurements taken by physicians can be higher than if a nurse or medical assistant performs the exam. This is often referred to as the “white coat effect” or “white coat hypertension” and is an illustration of how anxiety directly affects BP. About 10% to 20% of individuals with high BP in a medical office setting will have normal BP at home. A white coat effect can also be seen among individuals on BP medication; one study of patients with persistent high BP in the medical office setting despite being on three medications showed that 37% of them had normal BP recordings outside of the office.

If you feel you may be experiencing the white coat effect, please discuss with your medical provider how to obtain measurements in different settings. For a relatively low cost, you can purchase a home monitoring device and track your recordings. Additionally, some medical offices offer 24-hour ambulatory BP monitoring, which in many cases will be covered by Medicare or your health insurance.

Once you and your provider have confidence that your measurement is accurate, you can then collaborate on how to best approach and manage your blood pressure and well-being.


In good health,

Dr. Narrett