How useful is a casual BP measurement?

Blood pressure (BP) varies continuously dependent on numerous personal and external factors as well as on the way it is measured and the methodology used. A casual BP reading may give some clues about a person's cardiovascular health, but risk can only be determined with repeated careful measurements. If high (≥140/90), systematic measurement following approved guidelines using a validated monitor is necessary, especially if the person is symptomatic and/or BP ≥180/120. A low casual BP (<90/60) should be similarly rechecked, especially if related symptoms are present. Despite the availability of guidelines for measuring BP, there is often poor compliance with these standards leading to less-than-ideal risk assessment. The lack of regulation of what BP home monitors are available to purchase, ignorance about how to measure BP accurately, the use of unvalidated monitors and of incorrect cuff sizes may lead to significant under- or over-assessment of BP with potentially avoidable consequences. Casual BP measurements, especially if elevated, need a systematic non-casual approach to remeasurement and interpretation.