High blood pressure—hypertension—refers to blood pushing against the walls of the arteries with chronically elevated force. Blood pressure that rises above normal levels and remains high can lead to serious health problems including heart attack, heart failure, stroke, and kidney failure.
Blood pressure is measured in millimeters of mercury (mmHg). The top number, known as the systolic pressure, represents the pressure within the arteries when the heart contracts while pumping blood. The bottom number, diastolic pressure, represents the pressure in the arteries when the heart relaxes between beats and fills with blood.
