Monitoring your blood pressure at home can give a more accurate reading

It is not unusual for a person’s blood pressure to differ substantially when measured at home, versus at the doctor’s office, and there are many reasons for that.

Some people suffer from anxiety at the doctor’s office, called “white coat syndrome.” Others may have circumstances that don’t make for ideal readings. Maybe the patient was stuck in traffic and running late which is making them anxious. Maybe they were talking to the nurse when the blood pressure was being taken or sitting on the exam table with their legs swinging.

The discrepancy is enough that in 2017, the American College of Cardiology and the American Heart Association added a recommendation to their guidelines that people should also be taking their blood pressure at home to both confirm the diagnosis of hypertension and to ensure that blood pressure is being properly controlled with prescribed medications.

A recent study in England done across 142 general practices showed that is good advice. Patients in the study who self-monitored their blood pressure at home had significantly lower systolic blood pressure than those receiving treatment in the clinic setting only.

“Management of hypertension is critical to every patient and confirmation that the hypertension is being adequately treated is equally important,” said cardiologist Lawrence McAuliffe, MD, at Cape Cod Healthcare Cardiovascular Center in Hyannis. “So, the two components of that equation are: Is the blood pressure acceptable when the patient is seen in the office and is the blood pressure acceptable in the ambulatory (home) setting?”

How to Tell if Your BP Machine is Accurate

White coat syndrome is a real thing, he said, but before you can blame that for any discrepancies, first you have to confirm that the home blood pressure readings are actually acceptable and the elevated blood pressure in the office is the outlier. The best way to do that is to bring your home blood pressure machine to the doctor’s office and compare the reading the nurse or doctor gets with the one the patient gets on the home machine at the same visit.

There are so many different blood pressure monitors on the market that it can be confusing to choose the right one. A review of home blood pressure monitors tested by Doc Reviews indicated that the Oxiline Pressure X Pro is the most accurate machine of the 10 monitors they tested. It costs about $100, which is a fairly average cost for blood pressure monitors. It was also the top choice at Biohealth.edu. But even if your home monitor doesn’t match the accuracy of the reading at the doctor’s office, it is still possible to calibrate it so you get an accurate reading at home, Dr. McAuliffe said.

“I will tell patients no matter what machine you get, then you need to calibrate it with the fire station, your physician’s office, or a senior citizen’s center with a nurse or a well-trained nurse assistant taking it,” he said. “Even for those machines that don’t get the top-rated grade, the ability to compare the machine with the actual medical personnel machine blood pressure should accommodate or confer any differences.”

In other words, if you bring your blood pressure monitor into your doctor’s office and your doctor says your machine is either 10 millimeters high or 10 millimeters low compared to the doctor’s machine, then when you take your blood pressure at home simply add or subtract 10 millimeters to get an accurate reading.

Calibration is important because Dr. McAuliffe has had some patients with inaccurately high readings which would result in those patients getting too much medicine when their blood pressure is actually okay. He doesn’t want to overmedicate patients because that would cause their blood pressure to drop too low and make them feel lousy. But he also doesn’t want to miss blood pressure that is too high because that patient might need more medication to prevent a heart attack or stroke.

Taking Your BP at Home

Even though it’s important for patients to track their blood pressure at home, Dr. McAuliffe doesn’t recommend doing it 10 times each day because that just causes stress that can actually raise a person’s blood pressure.

“I’ll tell them to take it three or four times a week at different times of the day and in different settings so you can get an accurate survey of what their blood pressures really are,” he said. “That can help in terms of both timing of medication as well as whether we need an increase or decrease in dosing.”

When taking your blood pressure at home, the American Heart Association recommends the following guidelines:

• Do not smoke, drink caffeinated beverages or exercise within 30 minutes of measuring your blood pressure.
• Make sure your bladder is empty. A full bladder can temporarily raise blood pressure.
• Make sure the cuff on the blood pressure monitor is the right size for your arm. Cuffs that are too small raise blood pressure.
• Sit in an upright position with your back supported, your feet on the floor and your arm supported at heart level.
• Remove clothing covering the location of the cuff placement.
• Make sure the bottom of the cuff is directly above your elbow.
• Relax for five minutes before taking your blood pressure.
• Know that certain medications, including NSAIDs and decongestants, can raise blood pressure.
• Know that alcohol, smoking, excess salt and stress can also elevate blood pressure.

A normal reading is less than 120/80. If the top number is over 130 and the bottom number is over 80, talk to your doctor about ways you can lower your blood pressure with lifestyle modifications and medications.

Some newer blood pressure monitors have blue tooth technology to store data on apps or reading storage on the monitor itself, but an old-fashioned pad and pen work just as well. Record the date, time, your blood pressure and heart rate to share that information with your doctor.

“It’s important to record your heart rate as well as your blood pressure because some of the medications affect heart rate as well,” Dr. McAuliffe said. “Say you are on a calcium channel blocker and your heart rate is always in the 60s even though you may be on a lower dose. If your blood pressure is not under control, you can’t increase that med because it’s going to lower your heart rate further than is acceptable.”