## How to Check If Your Blood Pressure Monitor Is Accurate URL: https://www.cardilogai.com/guides/how-to-check-blood-pressure-monitor-accuracy Author: The CardiLog Team · Published: 2026-10-22 · Updated: 2026-10-22 Studies of home monitors brought in by their owners have found that many read differently from a careful clinic measurement. Here's how to check if your blood pressure monitor is accurate, using the test the American Medical Association publishes, what difference is acceptable, and how often to check again. ### Short answer Take your monitor to your doctor's office and compare it with the office device using the AMA's accuracy test, which alternates readings between the two. If your monitor's average is within 5 mmHg of the office reading, keep using it; at 6 to 10 mmHg, run a second comparison; more than 10 mmHg apart, replace it. Also check that the model is on a validated device list such as STRIDE BP or validatebp.org, and that the cuff fits your arm. The AHA suggests bringing your monitor in once a year. ### Why it's worth checking Several studies have compared people's own home monitors with careful measurements by trained staff: - Ringrose and colleagues (American Journal of Hypertension, 2017) tested 85 home devices. 69% read at least 5 mmHg away from the reference, and 29% at least 10 mmHg away. - Juraschek and colleagues (American Journal of Hypertension, 2024) ran the AMA test on 152 patients' devices. 22.4% failed, with a systolic difference over 10 mmHg. - The ACCU-RATE study (British Journal of General Practice, 2020) bench-tested 331 home monitors. 96% of validated monitors passed against 64% of unvalidated ones, and 95% of monitors in use for 4 years or less against 74% of older ones. A monitor that reads 10 mmHg high can make your blood pressure look like it needs more treatment than it does, and one that reads low can hide a problem. ### The AMA accuracy test, step by step The American Medical Association's SMBP device accuracy test, published with the AHA's Target: BP program, is done at your clinic with a staff member and the office's own device. After resting, as for any reading, five readings are taken in order: - A: your monitor. - B: your monitor. - C: the office device. - D: your monitor. - E: the office device. Then the readings are compared in up to two steps: - Step 2: average B and D, and compare that with C. Less than 5 mmHg apart, your monitor can be used. 6 to 10 mmHg apart, go on to step 3. More than 10 mmHg apart, replace it. - Step 3: average C and E, and compare that with D. 10 mmHg or less, your monitor can be used. More than 10 mmHg, replace it. The AMA sheet doesn't say what to do at exactly 5 mmHg, so ask the person running the test. It recommends doing the test before you start using a monitor, then once a year or whenever readings seem off. ### Check the model is validated A validated monitor has passed an independent accuracy study against a recognized protocol, such as the ISO 81060-2:2018 universal standard. You can look up a model on STRIDE BP, which lists devices whose validation studies it has approved, or in the US on the AMA's Validated Device Listing at validatebp.org. Validation is a property of the model, not of your particular unit, so a validated monitor still benefits from a clinic comparison. Our guide to [validated home blood pressure monitors](https://www.cardilogai.com/guides/best-home-blood-pressure-monitors) explains how to read those lists. ### Rule out the cuff and your technique Some "inaccurate monitor" problems are really cuff or technique problems. The AHA notes that a cuff of the wrong size causes inaccurate readings, and in the Ringrose study larger arm circumference predicted higher readings. Before blaming the monitor: - Measure your arm and check the cuff size with our [cuff size chart](https://www.cardilogai.com/guides/blood-pressure-cuff-size-chart). - Follow the measuring routine in our [guide to accurate home readings](https://www.cardilogai.com/guides/how-to-take-accurate-blood-pressure-measurements). - Allow time after coffee, exercise or a cigarette, as in [how long to wait before taking your blood pressure](https://www.cardilogai.com/guides/how-long-to-wait-before-taking-blood-pressure). If you use a wrist monitor, holding it at heart level matters even more. Our guide to [wrist vs upper-arm monitors](https://www.cardilogai.com/guides/wrist-vs-arm-blood-pressure-monitor) explains why. ### How often to check again Sources differ, and none sets a firm schedule: - The AHA's patient guidance: bring your monitor to your appointment once a year, or as the manufacturer directs. - The AMA test sheet: annually, or any time readings seem questionable. - Microlife, one manufacturer, recommends a 2-yearly accuracy test, and one after the monitor has been dropped. - The 2024 ESC guideline: ask for accuracy to be checked from time to time; devices older than 4 years may be inaccurate and should be replaced if they are. The AHA's 2019 statement on measurement notes there's no standard protocol for recalibrating home devices once they leave the factory, which is why the clinic comparison is the practical check. ### Home vs clinic: monitor error or white coat effect? If your home readings are much lower than your clinic readings, it could be your monitor, or it could be the white coat effect, where the clinic setting itself raises your blood pressure. The side-by-side test separates the two: if both devices agree when used together, the gap comes from the setting, not the monitor. In the CardiLog app you can tag readings with a location (Home or Clinic). Once you have 5 or more home readings and 3 or more clinic readings, CardiLog flags a possible white coat effect when the clinic systolic average is 10 mmHg or more above home. Our page on [white coat syndrome](https://www.cardilogai.com/use-cases/white-coat-syndrome) covers what to do with that pattern. ### Checking your monitor in brief - Compare it at the clinic: The AMA's test takes five readings, alternating between your monitor and the office device, then compares them. - Within 5 mmHg is fine: Under 5 mmHg apart, keep using it. More than 10 mmHg apart, the AMA says replace it. - Check it's validated: In one study, 96% of validated monitors passed bench tests compared with 64% of unvalidated ones. - Recheck once a year: The AHA suggests an annual check, and the 2024 ESC guideline says devices over 4 years old may be inaccurate. ### FAQ #### How do I know if my blood pressure monitor is accurate? Take it to your doctor's office and compare it with the office device using the AMA's accuracy test, which alternates five readings between the two. Also check the model is on a validated device list such as STRIDE BP or validatebp.org. #### How much difference between my monitor and the doctor's is acceptable? In the AMA's test, less than 5 mmHg means your monitor can be used. A difference of 6 to 10 mmHg calls for a second comparison, and more than 10 mmHg means replace the monitor. #### How often should a home blood pressure monitor be checked? The AHA suggests once a year, or as the manufacturer directs. The AMA's test sheet says annually or whenever readings seem off. The 2024 ESC guideline notes that devices older than 4 years may be inaccurate. #### Does FDA clearance mean a monitor is validated? No. A model being FDA cleared or sold in a pharmacy doesn't by itself mean it passed an independent validation study. Look the model up on STRIDE BP or validatebp.org. #### Can I calibrate a blood pressure monitor at home? Not reliably. The AHA's 2019 statement notes there's no standard protocol for recalibrating home devices after they leave the factory. The practical check is a side-by-side comparison at your clinic. ### Sources - [AMA / AHA Target: BP: SMBP Device Accuracy Test (2018)](https://targetbp.org/wp-content/uploads/2018/09/SMBP-Device-Accuracy-Test.pdf) - [American Heart Association: Monitoring your blood pressure at home](https://www.heart.org/en/health-topics/high-blood-pressure/understanding-blood-pressure-readings/monitoring-your-blood-pressure-at-home) - [Muntner P et al. Measurement of Blood Pressure in Humans: AHA Scientific Statement. Hypertension 2019](https://pmc.ncbi.nlm.nih.gov/articles/PMC11409525/) - [McEvoy JW et al. 2024 ESC Guidelines for the management of elevated blood pressure and hypertension. Eur Heart J 2024 (section 5.2)](https://academic.oup.com/eurheartj/article/45/38/3912/7741010) - [Ringrose JS et al. An assessment of the accuracy of home blood pressure monitors when used in device owners. Am J Hypertens 2017](https://pubmed.ncbi.nlm.nih.gov/28430848/) - [Juraschek SP et al. Comparison of home and office blood pressure devices in the clinical setting. Am J Hypertens 2024](https://pubmed.ncbi.nlm.nih.gov/38150380/) - [Hodgkinson JA et al. Accuracy of blood-pressure monitors owned by patients with hypertension (ACCU-RATE study). Br J Gen Pract 2020](https://pubmed.ncbi.nlm.nih.gov/32482629/) - [Microlife: FAQ on blood pressure monitors](https://www.microlife.com/magazine/blood-pressure/faq-blood-pressure-monitors) - [STRIDE BP: Validated blood pressure monitors](https://www.stridebp.org/bp-monitors) - [AMA: US Validated Device Listing](https://www.validatebp.org/)