How to Check Your Blood Pressure Monitor Is Accurate

The most reliable at-home accuracy check doesn't happen at home at all. Bring your own monitor to your next appointment and compare it against the reading taken there.

• Tell the staff you'd like to compare your device against their measurement.
• Have your reading taken close in time to theirs, on the same arm where practical.
• Note both results so you can see how closely they track.

This checks the whole chain at once: the device, your cuff, and your technique.

For the comparison to mean anything, measure the way you normally should:

• Rest quietly beforehand and sit properly, back supported, feet flat, arm at heart level.
• Use your correctly sized cuff on a bare arm.
• Stay silent during both readings.

If your technique is off, the comparison will blame the device unfairly. Our how-to-use-a-blood-pressure-monitor guide covers the routine.

Two accurate instruments won't produce identical numbers, and blood pressure shifts minute to minute, so expect some difference. We won't put a specific acceptable figure on it, because judging whether the gap matters strays into interpretation, and that's your doctor's role. If your readings track your clinic's reasonably and consistently, that's reassuring. Ask the staff or your doctor to help you judge the comparison.

A consistent gap doesn't automatically mean the device is broken. Work through the usual causes first:

• Cuff size and fit: the most common culprit (see blood-pressure-cuff-size-guide).
• Technique: posture, rest, and arm height.
• Cuff condition: an old cuff may leak or lose grip.

If those check out and a clear gap remains, move on to recalibration or replacement.

Home monitors can drift over years of use.

• Check your manual and manufacturer for a recalibration or servicing option; some brands offer it, and some suggest periodic checks.
• Replace a monitor that's damaged, out of warranty, or persistently off after you've ruled out cuff and technique.
• A worn cuff can often be replaced on its own with the correct size for your model.

When in doubt about whether a difference matters for your care, ask your doctor rather than deciding from the numbers yourself.