What is blood pressure?

The top number, systolic pressure, is measured when the heart beats, and the bottom number, diastolic pressure, when it rests between beats. Both are measured in millimetres of mercury (mmHg). A reading around 120/80 or below is generally considered healthy, while persistent readings of 140/90 or higher are often classed as high blood pressure, or hypertension, though some guidelines use 130/80. The WHO estimates about 1.3 billion adults worldwide have hypertension, many without knowing, which is why it is called a “silent killer”. Less salt, regular exercise and healthy weight help lower it.