What do the numbers mean?

Blood pressure is really two measurements, separated by a slash when written down, such as 120/80. You may also hear someone say a blood pressure is "120 over 80."
The first number is the systolic blood pressure. This is the peak blood pressure when your heart is squeezing blood out. The second number is the diastolic blood pressure. It's the pressure when your heart is filling with blood--relaxing between beats.
A normal blood pressure is less than 130/85. High blood pressure is 140/90 or higher. If your blood pressure is between 120/80 and 140/90, you have something called "prehypertension."

How is high blood pressure diagnosed?
Blood pressure is measured by putting a blood pressure cuff around your arm, inflating the cuff and listening for the flow of blood. Your doctor will measure your blood pressure at more than one visit to see if you have high blood pressure.

How often should I have my blood pressure checked?
Even in children, blood pressure should be checked occasionally, beginning at about age 2. After age 21, have your blood pressure checked at least once every 2 years. Do it more often if you have had high blood pressure in the past.