A blood pressure reading less than 120/80 millimeters of mercury is considered normal for adults over 20 years old, according to the American Heart Association. People over 50 years old are at high risk for cardiovascular disease if the top value is high.
Blood pressure is recorded with the systolic value on top and the diastolic value on the bottom. A person with a systolic blood pressure reading consistently greater than 140 millimeters of mercury or a diastolic value consistently greater than 90 millimeters of mercury is considered to have hypertension, as defined by the American Heart Association. Hypertension increases the risk of cardiac and vascular diseases. Blood pressure tends to rise as a person ages.