Health: A-Z Health Glossary - B is for 'Blood Pressure'
Blood pressure is the force that the blood exerts against the walls of arteries. The heart beats 60-70 beats per minute and each time it beats, it pumps blood into the arteries, which is when the blood pressure is at its highest and it rests between heart beats, when blood pressure is at its lowest. 
Blood pressure is recorded as two numbers:
* systolic pressure - this is the pressure when the heart pushes blood out into the arteries (when the heart beats)
* diastolic pressure - this is the pressure when the heart relaxes between beats
Blood pressure measurement is written as one number above or before the other, with the systolic number on top and the diastolic number on the bottom. For example, a blood pressure measurement of 120/80 mmHg (millimeters of mercury) is expressed verbally as "120 over 80."
* Blood pressure varies constantly due to many factors such as body temperature, diet, emotional stress, posture, exercise, health and medication/drugs
* High blood pressure is called "the silent killer" because is has no apparent symptoms
* Many people with high blood pressure do not realise they have this conditions
* A high salt diet affects blood pressure by increase it
Measuring blood pressure is vitally important as high blood pressure does not often have any symptoms until it is too late and the person has a heart attack or stroke.
The table above shows the different blood pressure measurement for adults over 18 years of age (Blood pressure measurements for adults (mmHg))
Blood Pressure Measure Systolic Diastolic
Normal < 120 < 80
Pre-hypertensive 120-139 80-89
High Blood Pressure Measure Systolic Diastolic
Stage 1 140-159 90-99
Stage 2 > 160 > 100