Blood pressure is the pressure of the blood against the walls of the arteries resulting from two forces. One is created by the heart as it pumps blood into the arteries and through the circulatory system. The other is the force of the arteries as they resist the blood flow.
According to the American Heart Association, Blood pressure below 120 over 80 mmHg (millimeters of mercury) is considered optimal for adults. A systolic pressure of 120 to 139 mmHg or a diastolic pressure of 80 to 89 mmHg is considered “pre-hypertension” and needs to be watched carefully. A blood pressure reading of 140 over 90 or higher is considered high.