Blood pressure at home

High blood pressure usually causes no symptoms, so the only way to know yours is to measure it. And one reading in a doctor's office can mislead in either direction. A week of readings taken at home tells me far more than a single number from a clinic.

Some people run high in the office from nerves and are fine at home. Others look fine in the office and run high the rest of the week. Readings taken in a clinic are often the highest ones a person ever records. One reading cannot sort these apart. A week can.

The method matters, because small things change the number. This is the routine the American Heart Association and American Medical Association describe:

Use an upper-arm cuff that has been checked for accuracy, in the right size for your arm.
No caffeine, exercise or tobacco for 30 minutes beforehand.
Sit with your back supported, feet flat on the floor, and your arm resting on a table at heart level, with the cuff on bare skin.
Sit quietly for five minutes first.
Take two readings, one minute apart, in the morning and again in the evening, for seven days.

Write down every reading, not only the good ones. What your doctor will look at is the average, not the highest or the lowest number of the week.

Blood pressure also has company. It often travels with insulin resistance, which is when the body responds less well to insulin, and with sleep apnea, which is repeated pauses in breathing during sleep. Alcohol and several common medicines, including some pain relievers and decongestants, can raise it too. So a week of numbers is the start of a conversation about why, not only about how high.

Two limits. Home readings do not diagnose anything on their own, and a home cuff is only as good as the routine around it. And if you take blood pressure medicine, do not change it based on your own readings. Bring the log to the doctor who prescribes it.

When to get care now. Call 911 for signs of a heart attack: chest pressure or pain, shortness of breath, pain in the arm, back, neck or jaw, nausea, a cold sweat or sudden unusual tiredness. In women these can come without chest pain. Call 911 for signs of a stroke: one side of the face drooping, weakness in one arm, or trouble speaking. Call 911 as well for a reading at or above 180/120 together with chest pain, breathlessness, severe headache, vision change, weakness or difficulty speaking. Do not drive yourself.

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