High blood pressure, or hypertension, is when the pressure of blood pumping against artery walls is higher than it should be. It's defined as having a systolic (upper number) blood pressure reading of 130 millimeters of mercury (mmHg) or higher, and/or a diastolic (lower number) blood pressure reading of 80 mmHg or higher. High blood pressure is considered a major risk factor for cardiovascular disease, and it can also damage the brain, kidneys, and eyes. Nearly half of all U.S. adults have high blood pressure, including nearly 75% of those over 60 years old. High blood pressure usually doesn't have symptoms, which is why it's known as the "silent killer." There are two types of high blood pressure: primary (also called essential) hypertension, which doesn't have a known cause, and secondary hypertension, which is the result of other conditions that raise blood pressure. Hypertension can be hereditary, which means if your parents o...