What is blood pressure?
Sorry if this is overly simplistic.
The heart is a pump. When the heart squeezes it pumps blood out with a pressure.
When it relaxes there is still some pressure in the circulation pushing things forward.
When the blood pressure machine tries t measure the pressure it has to squeeze your arm hard enough to stop blood flow. i.e. the pressure has to match/exceed the pressure with which the blood is trying to explode out of the blood vessels. This is the top number.
This is why we try to keep pressure controlled with medicines to control the pressure if it is too high.
What are the dangers ?
If blood pressure is very high it can explode out of the blood vessels and cause a stroke. If it is high, it can combined with diabetes, smoking and cholesterol, FH etc. cause damage to the blood vessel wall thickening it with rubbish ( an atheroma). This apart from limiting the flow to your heart, legs,kidneys,brain and cause problems such as angina, cramps etc.
It can cause problems if this rubbish breaks off and blocks blood vessels further downstream.The brain and heart have a limited supply and if this gets blocked off the brain or heart tissue die without the oxygen in the blood.
Looking for a blood pressure machine to monitor your blood pressure ?
This links to the British Hypertensive Societies approved monitors.
This does not mean that other monitors are no good.
If the monitor has been approved by an appropriate European Body and it is sold by a reputable organisation then the monitor will have some value,and will hopefully at least be able to indicate a trend.
I would tend to advise going for ones that monitor blod pressure above your elbow rather than wrist or thumb type BP monitors which I do not have enough experience off to recommend.
What should my blood pressure be ?
If you are otherwise well we accept a blood pressure of 140 / 80 mmHg.
If it is higher than 160/100 we generally treat you.
If it is in between it depends on your overall risk factor of heart disease and stroke and other issues.
We do not generally start treatment on the basis of one reading alone. The target blood pressure depends on your health.