Blood pressure (BP) is the pressure exerted by circulating blood upon the walls of blood vessels. It is one of the vital signs of the body. Blood pressure is usually expressed in terms of the systolic (maximum) pressure over diastolic (minimum) pressure and is measured in millimeters of mercury (mmHg). According to WHO standards, normal blood pressure is categorized in the range of 120-129/80-84 mmHg.
Blood pressure varies depending on situation, activity, and disease states. Blood pressure that is low due to a disease state is called hypotension and blood pressure that is consistently high is hypertension. Long term hypertension is a risk factor for many diseases, including heart disease and stroke. Long term hypertension often goes undetected because of infrequent monitoring and the absence of symptoms.