What is high blood pressure ?

High blood pressure (hypertension)

High blood pressure (also known as hypertension) is a condition in which the pressure in your arteries is higher than is normally needed to keep blood moving round the system.

This gives the heart extra work and over time the pressure can damage sensitive organs like the eyes, kidney and brain.

Blood pressure in the movies!

No, not movies that explain what is high blood pressure! But, have you ever seen one of those films in which someone is injured, resulting in a pulsating jet of blood? Usually someone is struggling to staunch the flow unsuccessfully. Not a pleasant image perhaps but it does happen in real life and it is a graphic demonstration of the pressure of blood in arteries.

Heart work

To pump blood around the body, the heart squeezes, then relaxes, squeezes again and so forth. It is moving blood around the body to where it is needed.

If you were given a hand pump to push blood around a body you would probably be out of breath before too long, it’s a lot of work.

When pumping a fluid through tubes, how hard you have to push will depend on how wide the tubes you are pushing it through are. Narrow tubes will create resistance as you pump and you would have to push harder to keep the blood flowing. Wider tubes will allow easy flow. The main determinant of the pressure in the system is therefore the resistance.

HBP - its all about the resistance

To understand high blood pressure, you need to know that your heart pumps blood to the body through arteries. The resistance it has to push against is determined by the state of these blood vessels - arteries have muscular walls that can tighten and make the vessels smaller.

The main abnormality in hypertension is that the blood vessels (arteries) are providing more resistance than they should. (It helps to understand why, but we'll talk about that later). As a result the heart has to pump harder and the blood in the arteries is under higher pressure.

What is normal blood pressure?

Research has determined a level of blood pressure that can be taken as average or 'normal'.

If your pressure is just over normal, with time it could rise further until you are in the high blood pressure category. This is called pre-hypertension. It is also associated with an increased risk of complications.

If you have pre-hypertension, prudent lifestyle changes or alternative remedies can help keep your pressure down.

Blood pressure is a continuum and it can be misleading to talk of a fixed line demarcating what is normal from what is high blood pressure and pre-hypertension. Many people have levels much lower than 'normal' and don't have any problems.

  • Normal blood pressure is a reading under 120/80
  • Pre-hypertension is a reading between this and 140/90
  • High blood pressure is anything over this.

(I'll talk more about the figures in the section on blood pressure readings)


How does an individual know what is high blood pressure, if their measurements go up and down during the course of 24hrs? It is low during sleeping hours and rises very high during exercise or in situations of anxiety or emotional stress. It can be high from discomfort or climbing a few stairs, after a hot coffee or a big meal.

Generally speaking, everyone has a fairly constant pressure when relaxed and at rest, and that is what we are concerned with when discussing and measuring blood pressure.

Essential Hypertension - do you have to have it?

The commonest form of high blood pressure by far, is known (to doctors) as primary hypertension, or essential hypertension. (I am not sure why the latter phrase stuck - its not compulsory as far as I know!). Now you know, you won't be confused when you come across the term.

No one is sure why blood pressure begins to rise with age. The mechanisms are well known, but not what actually gets the process going.


What is known for sure is that allowing your blood pressure to remain high can take years off your life and put you at risk of serious complications.

Delicate (and very important) organs such as kidneys, eyes, and the brain are at risk of damage. Of course your heart suffers too.

It is up to you therefore to be as determined as you can in finding ways to reduce your blood pressure and keep it down.

I discuss complications of high blood pressure in more detail here.

Secondary hypertension

This is high blood pressure that is related to a distinct underlying disease, such as kidney disease, some cancers etc.

Other forms of high blood pressure

• Orthostatic hypertension

A very unusual form of high blood pressure is called orthostatic hypertension. This is a rise in blood pressure that occurs only on standing up. Usually, on standing, blood pressure drops very slightly. The change in posture causes more blood to end up in the leg veins, and creates a greater height for the heart to pump blood to. There is therefore a brief drop in blood pressure and then the body control mechanisms react fast to boost blood pressure back to, or close to, its previous level.

In orthostatic hypertension it is thought that the control mechanisms overcompensate with the result that blood pressure is reset to a higher level.

Conditions associated with this, in addition to essential hypertension, include diabetes, and a group of disorders of the nervous system called autonomic dysfunction.

• Pregnancy induced hypertension

This is discussed in detail here.

• White coat hypertension

What is high blood pressure that appears only in the clinic? Read about white coat hypertension here.

What is high blood pressure ?

The KEY facts...

  • You have high blood pressure when the pressure of blood in your arteries is higher than average. (Over 140/90).
  • High Blood pressure means that your heart is doing extra work - over the years it can cause cumulative damage.
  • Your blood vessels are under more pressure than necessary, with the blood inside pushing against the walls - this too over the years can store up trouble for you.
  • It is in your interest to keep your blood pressure within the normal range.

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