Blood pressure is the pressure or force of blood against the walls of blood vessels as it circulates. Blood pressure is most commonly measured in the brachial artery of the arm and it is expressed as two numbers. Systolic blood pressure (the top or higher number) is the pressure in the artery when the heart contracts and diastolic blood pressure (the bottom or lower number) is the pressure in the artery when the heart relaxes between beats. Blood pressure normally changes throughout the day, but when either systolic or diastolic pressure stays constantly high it is called high blood pressure (hypertension).
Blood pressure that is consistently more than 140/90 mmHg is considered high, but if you have diabetes or chronic kidney disease, 130/80 mmHg is high.