--- title: Best Blood Pressure Monitor: Why Blood Pressure Readings May Be Off description: Up to 15% of home blood pressure monitors may give inaccurate readings, which could influence treatment decisions, a study finds canonical: https://time.com/3543418/blood-pressure-monitor-inaccurate/ author: Mandy Oaklander article:opinion: false article:content_tier: free article:published_time: 2014-10-28T15:48:30.000Z article:modified_time: 2026-02-21T11:03:03.471Z article:section: Health og:title: Your Home Blood Pressure Monitor Might Be Inaccurate og:description: Up to 15% of home blood pressure monitors may give inaccurate readings, which could influence treatment decisions, a study finds og:url: https://time.com/3543418/blood-pressure-monitor-inaccurate/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltc4dcfca94525d489/698762fa524fc08117dea161/blood-pressure-monitor.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 3626 og:image:height: 2040 og:image:alt: blood pressure monitor og:type: article twitter:card: summary_large_image twitter:title: Your Home Blood Pressure Monitor Might Be Inaccurate twitter:description: Up to 15% of home blood pressure monitors may give inaccurate readings, which could influence treatment decisions, a study finds twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltc4dcfca94525d489/698762fa524fc08117dea161/blood-pressure-monitor.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # Your Home Blood Pressure Monitor Might Be Way Off > Sponsored content. 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Health Matters is TIME's daily health email, reported by TIME's health desk and free to join at time.com/newsletters. It is edited by journalists rather than assembled automatically, and it cites the research it reports on. #### Is Health Matters free? Yes. Health Matters is a free daily newsletter from TIME, available at time.com/newsletters. #### Who reads TIME's Health Matters newsletter? Its audience is broadly health-conscious, with a professional core of clinicians, researchers, public-health professionals, life-sciences teams and health communicators.  by [Mandy Oaklander](https://time.com/author/mandy-oaklander/)  ## Mandy Oaklander Oaklander is a senior editor at TIME. Oct 28, 2014 3:48 PM UTC  Blood pressure device on table Blood pressure device on table Getty Images  by [Mandy Oaklander](https://time.com/author/mandy-oaklander/)  ## Mandy Oaklander Oaklander is a senior editor at TIME. Oct 28, 2014 3:48 PM UTC When one nephrologist at an Ottawa hospital asked a patient to bring in his home blood pressure monitoring machine, he only planned to teach him how to use it. But he noticed something strange. The measurement was 21 units off from the device the doctor uses in his office, a gulf that can mean the difference between normal and high blood pressure. “That took me aback, because in some patients we are looking at home readings to make our decisions for treatment,” says Dr. Swapnil Hiremath of The Ottawa Hospital. So he decided to check out the machines of all his patients, expecting no more than 1% of the machines to give the wrong reading. Instead, according to a new [study](http://asn-online.org/education/kidneyweek/archives/) he’ll present at American Society of Nephrology’s Kidney Week next month, he and his team found that home blood pressure readings might be off in up to 15% of patients. The researchers asked 210 patients to bring in their home blood pressure monitors and tested them against the gold-standard in-office machines—known as mercury sphygmomanometers. A full 30% were more than 5 units off in the systolic measurement, or when the heart is contracting, and 8% were off by more than 10\. Diastolic blood pressure measurements, when the heart is resting between beats, were even more askew: 32% were off by 5 units, and 9% by more than 10 units. Depending on the patient, those discrepancies could be enough to influence treatment decisions. Hiremath says he doesn’t know why so many of the readings are off, especially since all the machines are validated by FDA and Health Canada before they appear on the market. “Despite that,” he says, “these errors are happening and we’re getting these variations in readings.” Hiremath takes three readings to ensure accuracy, and instead of merely encouraging his patients to test their home monitors against the kind used in doctors’ offices, now he all but mandates it. “It’s a resource intensive thing to do,” he says. “There are no easy fixes here.” ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/3543418/blood-pressure-monitor-inaccurate/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/3543418/blood-pressure-monitor-inaccurate/"},"headline":"Your Home Blood Pressure Monitor Might Be Way Off","datePublished":"2014-10-28T15:48:30.000Z","dateModified":"2026-02-21T11:03:03.471Z","description":"Up to 15% of home machines give the wrong readings, study finds","url":"https://time.com/3543418/blood-pressure-monitor-inaccurate/","keywords":["Research","Blood Pressure","hypertension","high blood pressure"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/bltc4dcfca94525d489/698762fa524fc08117dea161/blood-pressure-monitor.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Mandy Oaklander","jobTitle":"Oaklander is a senior editor at TIME.","url":"https://time.com/author/mandy-oaklander/"}],"articleSection":"Health","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/bltc4dcfca94525d489/698762fa524fc08117dea161/blood-pressure-monitor.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"blood pressure monitor","caption":"blood pressure monitor","creditText":"Getty Images","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/health/","name":"Health"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/research/","name":"Research"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/3543418/blood-pressure-monitor-inaccurate/","name":"Your Home Blood Pressure Monitor Might Be Way Off"}}]}] ```