What is High Blood Pressure?

To understand high blood pressure, you must first understand what blood pressure is. Very simply, this refers to the force of blood against the walls of your arteries. Think of this as water rushing through a pipe. You may find it easier to understand more about blood pressure and blood flow if you understand more about how your heart works.

High blood pressure can cause damage to the walls of your arteries. This can create scarring, which in turn causes fatty plaque to build up, contributing to the narrowing and blocking of your arteries. Your heart will become strained and weakened. Blood vessels in your brain can burst—causing a stroke—if your blood pressure is very high. Your blood pressure varies during the day, moving up and down, often linked to activity or the lack of it (for example, your blood pressure is usually lowest at night but rises quite quickly once you get out of bed in the morning). Everyone's blood pressure goes up occasionally if, for example, something has frightened you, or you are angry or feeling stressed. But when your blood pressure remains high for long periods of time it means you have high blood pressure. This is also referred to as hypertension, a term you may hear your doctor use.

Blood pressure is measured with two numbers—systolic and diastolic. The systolic is an indication of how much pressure there is in the arteries (the maximum amount) when the left ventricle of the heart contracts. The diastolic indicates what the pressure is in your arteries between heartbeats.

There are several categories of blood pressure levels, which are all measured as mmHg (millimetres of mercury). Let's look at some numbers:

Normal blood pressure 120 mmHg or less (systolic) and 80 mmHg or less (diastolic)

Prehypertension 120-139 mmHg (systolic) or 80-89 mmHg (diastolic)

High blood pressure
Stage 1 = 140-159 mmHg (systolic) or 90-99 (diastolic)
Stage 2 = 160 mmHg or higher (systolic) or 100 mmHg (diastolic)

High blood pressure is referred to as a "silent" disease, because it often has no symptoms. This is why regular check-ups with your doctor are a good idea.