If your home blood pressure reading is different from the doctor’s office, from one monitor to the next, or from one minute to the next, then you may wonder about accuracy. There are plenty of factors that may affect our measurements: how we sit, the tightness of our cuff, our lifestyle patterns, stress, and distractions when taking a measurement can all affect the result.
If you’ve noticed a difference in your blood pressure readings and want to learn more, here are some tips to make sure that your measurements are accurate.
How to Take the Most Accurate Measurement
Here are several common problems that account for inaccurate blood pressure measurements.
4- O’Brien E, Asmar R, Beilin L, et al. European Society of Hypertension recommendations for conventional, ambulatory and home bloodpressure measurement. J Hypertens 2003; 21: 821-848.
Get the Right Size Cuff
Most errors are from having the wrong size of cuff. A cuff that is too small cuff can cause 2-10 mm/Hg higher blood pressure.
- Most cuffs will list the size range. Measure around your arm with a tape measure to ensure you have the right cuff size.
- Ask your care team to help you size your arm for the correct cuff
- The cuff should fit 1/2 inch above the elbow, and snugly so 2 fingers cannot be wiggled beneath it.
Wear the Cuff on Skin, not Clothing
Putting the cuff over clothing can cause blood pressure reading to appear 10 to 50 points higher.
- Roll up your sleeve before measuring.
Take Three Readings and Average Them
The American Heart Association recommends that the most accurate measurement is:
- After resting in a chair for around 5 minutes, with feet flat on the floor, and legs and arms uncrossed.
- Taken three times, with each reading spaced 1 minute apart.
- The reading that you use is the average of all three readings.
Other Factors that Exaggerate Blood Pressure Results
Things that cause higher-than-normal readings:
- Stress: Stress or nervousness before or during a measurement may raise cortisol levels, and cause a rise in blood pressure. Take some deep breaths before and during the measurement to lower stress.
- Salty foods: May cause higher readings for a few days afterward.
- A full bladder: This can add up to 10 to 15 points. Use the restroom before getting your blood pressure to get a more accurate reading.
- Talking: Speaking during the measurement may raise blood pressure by 10 to 15 points. Try to avoid talking while taking a measurement.
- Being cold: Shivering raises body activity and thus blood pressure. If you can’t control the temperature in the room, then make a note that this may have been a factor contributing to the high reading.
- Alcohol, caffeine and tobacco: Avoid consuming these 30 minutes before taking a reading, as they will cause a higher than normal blood pressure.
- Exercise: Blood pressure may be temporarily higher after exercise. After exercise, please rest for 30 minutes before checking blood pressure.
Things that cause lower-than-normal readings:
- Eating a large meal: digesting food actually lowers blood pressure: Take your blood pressure in the morning before eating anything, OR 30 minutes or more after your last bite of food.
- Dehydration: this may cause lower blood pressure until you correct it. If you’ve just come from the sauna, hot tub, or jacuzzi, or if you’ve been sweating a lot, this can cause a LOW blood pressure. Drink some water, eat some fresh fruits and vegetables, and recheck in an hour.
Questioning Device Accuracy
- It is never recommended to compare one digital blood pressure machine to another.
- Avoid using a wrist blood pressure monitor. There are too many variables that may affect readings and make them inconsistent and unreliable.
- The American Heart association recommends that to ensure accuracy of your blood pressure monitor, you should compare it against the doctor manually reading your blood pressure using a sphygmomanometer.
- To do this test, take your blood pressure monitor to the doctor’s office and do a side-by-side comparison, with the readings spaced 1 minute apart.
- Blood pressure monitors are typically calibrated from the factory. Industry standards note that a blood pressure monitor will gradually lose it’s accuracy over time. Replace your blood pressure monitor every 2 years.
- If you drop your blood pressure monitor, this may affect accuracy, even once. Try to keep your blood pressure monitor in a safe place where it will not be moved or transported too much.
Please contact you Care Team if you have any further questions!