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How To Measure Your Blood Pressure (And Why You Should)

Jun 18, 2019
By Malcolm Thaler
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What is high blood pressure? (it's more complex than you might think)

Why do we care about blood pressure? It’s just a number - well, two actually - the top number (the systolic blood pressure) representing the peak blood flow as the heart contracts, and the bottom number (the diastolic pressure) reflects the nadir as the heart relaxes. It turns out, of course, that both of these numbers mean a lot. High blood pressure is a major risk factor for heart disease, stroke, peripheral arterial disease, kidney disease and even dementia. The key is knowing what ‘high’ actually means.

The definition of what constitutes high blood pressure - also known as hypertension - has changed over time, and depends upon your age and other underlying health conditions you may have. In the most general terms, anything under 140/90 is considered healthy. Equally important as the actual numbers is how they fit in to your overall health. Your primary care clinician can put it all into context for you and help provide you with a more precise understanding of what is a healthy blood pressure for you.

So what is the best way to determine your blood pressure? Clinicians used to rely on readings taken in our offices as the most accurate measure of blood pressure. We would use those values to recommend treatments aimed at keeping your blood pressure in a healthy range, But recent research has taught us that readings taken at home are actually better at predicting your chances of developing heart disease, stroke and other complications of elevated blood pressure. In fact, many people who have high blood pressure in the doctor’s office have normal pressure at home (you may have heard this called “white coat” hypertension) and a small number of people have the opposite (called “masked” hypertension). In either case, it is the home readings that are the most reliable. If your blood pressure is deemed elevated at your doctor’s visit, you will likely be encouraged to take a series of home readings.

How to purchase a blood pressure cuff

Purchase an automatic monitor at your local pharmacy or online retailer; you will probably spend between $40 and $100, depending on how many bells and whistles you want, few of which add anything to the accuracy of the readings. Consumer reports and Wirecutter have some good recommendations. You want to buy an arm cuff, not a wrist or finger cuff. The cuff should fit your arm snuggly but not too tightly. If the cuff is too small, the readings will be falsely elevated. You should be able to fit two fingertips between your arm and the cuff before it is inflated. If the circumference of your arm at your biceps exceeds about 12 inches, you probably need a large cuff.

How to measure your blood pressure

Sit down and relax for at least five minutes. Have your arm supported at the level of your heart, e.g. resting on some pillows. Your back should be supported and straight, and your feet should be flat on the floor. Now take your first reading. Wait one minute and get a second reading. Discard the first reading – the second reading is the blood pressure to record.

When to measure your blood pressure

You should measure your blood pressure at different times of day, because it can and will vary hour to hour. You may find that it is a bit higher first thing in the morning and lower at night or shortly after exercise; this kind of variation is normal. At One Medical, we recommend checking once in the morning and once in the evening.

How often should you take your blood pressure?

If you are following up on a high reading at your clinician’s office, then twice a day - morning and night - for about a week should give you a good sense of where your blood pressure range really lies. This is also a good approach if you are monitoring a change in blood pressure medications. Otherwise, just the occasional reading is more than sufficient.

How to share your readings with your provider

Use the One Medical app to enter your readings under “health record”. When you’ve completed a week of readings, send a message to your healthcare provider with the readings you have taken. He or she will let you know what is the next best course of action and whether or not you should follow up with an office visit.

Don’t become too obsessed with obtaining multiple readings - there is no advantage to measuring your pressure more than the recommended two times a day. Overdoing and overthinking the whole process is almost guaranteed to raise your blood pressure! And don’t worry if you see numbers that appear high. Your clinician will be able to help you get your blood pressure under control with approaches ranging from diet changes and increased exercise, to meditation and even medications when needed. Blood pressure matters, but remember that it is only one piece of your overall health profile. Getting accurate home readings will allow you, in concert with your clinician, to ensure that your blood pressure is right where it should be.

For a quick guide to how you can adjust your lifestyle to help manage your blood pressure, and what medication options are available should they be needed, see our post here.

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Malcolm Thaler, One Medical Provider

Malcolm enjoys being on the front lines of patient care, managing diagnostic and therapeutic challenges with a compassionate, integrative approach that stresses close doctor-patient collaboration. He is the author and chief editor of several best-selling medical textbooks and online resources, and has extensive expertise in managing a wide range of issues including the prevention and treatment of cardiovascular disease, diabetes, and sports injuries. Malcolm graduated magna cum laude from Amherst College, received his MD from Duke University, and completed his residency in Internal Medicine at Harvard's New England Deaconess Hospital and Temple University Hospital. He joined One Medical from his national award-winning Internal Medicine practice in Pennsylvania and was an attending physician at The Bryn Mawr Hospital since 1986. He is certified through the American Board of Internal Medicine. Malcolm is a One Medical Group provider and sees patients in our New York offices.

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The One Medical blog is published by One Medical, an innovative primary care practice with offices in Boston, Chicago, Los Angeles, New York, Phoenix, the San Francisco Bay Area, Seattle, and Washington, DC.

Any general advice posted on our blog, website, or app is for informational purposes only and is not intended to replace or substitute for any medical or other advice. The One Medical Group entities and 1Life Healthcare, Inc. make no representations or warranties and expressly disclaim any and all liability concerning any treatment, action by, or effect on any person following the general information offered or provided within or through the blog, website, or app. If you have specific concerns or a situation arises in which you require medical advice, you should consult with an appropriately trained and qualified medical services provider.