Blood pressure is a measurement of the pressure exerted by blood flow against the walls of an artery during the two phases of the heartbeat - when the heart contracts and when it relaxes - that is why there are two numbers in a BP measurement. There is no normal blood pressure. AVERAGE blood pressure is around 120/80. The 120 is the pressure (measured in millimeters of mercury, or mm/Hg) exerted against your arteries when your heart is contracting. This is called the systolic pressure. The 80 is the pressure against your arteries when your heart is at rest between beats. This is referred to as the diastolic pressure. So, you can see how a BP that is too high can cause problems, because too much pressure is being placed on the arteries of the body. This means a higher risk of stroke, heart attack, and long term damage to the arteries. High BP can also damage organs, especially the kidneys, leading to renal failure. If your blood pressure is consistently over 135/85, you are considered to have hypertension (high blood pressure). One high BP reading is not sufficient to diagnose hypertension. You must monitor your BP over a period of time. Healthcare providers are becoming much more aggressive in treating hypertension because it s been shown to have a very big impact on minimizing the damage that can be done. Hypertension can be completely assymptomatic, yet can cause huge health problems. That is why hypertension is known as the silent killer .