Blood pressure is usually presented as systolic over diastolic pressures in mm of mercury (mmHg). The systolic pressure is measured when the heart contracts, and the diastolic pressure is measured when the heart is resting between beats.

Current UK guidance is that, ideally, blood pressure should be below 120/80mmHg.² However, most people’s blood pressure is within the range 120/80mmHg to 140/90mmHg, described as ‘pre- hypertension’. This term was proposed in the US in the 1960s,⁴ but is now starting to appear in the UK, although NHS Choices describes it as "high normal".^5 Blood pressure in this range indicates a likelihood of hypertension and associated morbidities developing if nothing is done to keep blood pressure under control.²