It is the pressure of circulating blood on the walls of blood vessels. Usually, it is expressed in terms of the systolic which is the maximum pressure during one heartbeat over diastolic which is minimum pressure in between two heart beats. it is measured in millimeters of mercury (mmHg). Normal blood pressure in a healthy adult is 120 millimeters of mercury systolic and 80 millimeters of mercury diastolic. The situation in which blood pressure is below the normal range is called hypotension, and pressure that is consistently high is termed as hypertension.