Blood pressure – do you know your numbers?

This article was written by London-based GP – Dr Nirja Joshi

What is blood pressure?

Blood pressure is a measure of the force of blood pumping around the body. It is measured in two numbers:

  1. the systolic (commonly referred to as the ‘top number’)
  2. the diastolic (the ‘bottom number’)

Essentially, this looks at the pressure when your heart pushes blood out (systolic), and the pressure when your heart relaxes (diastolic). This is measured as millimetres of mercury, or you may see it as mmHg (1).

Like any pumping system, it relies on the force of the pump (the heart) and the width of the pipes (the blood vessels). So if you have a weaker heart, for example in heart failure, that will impact your blood pressure, and if your arteries are blocked with cholesterol deposits this may make your pipes narrower which can also impact on your blood pressure (2). 

Why is it important?

A normal blood pressure is needed so that your body can get the oxygen needed to your organs, your muscles, your brain and even your heart (it needs it’s own blood supply too!). If your blood pressure is too low, then you may experience symptoms such as dizziness or fainting. Your blood pressure can fall with conditions such as heart conditions and severe infection (sepsis). However, sometimes this can be ‘physiological’, so for example, in pregnancy, your blood pressure may fall as blood vessels expand and some of the blood volume will be redirected to the baby. Equally, when you exercise, your blood vessels will expand or dilate, to get more blood flow to your muscles, but if you’re also dehydrated and losing water, you may feel faint during a workout. Premenopausal women also tend to have lower blood pressure compared to men of the same age. 

If your blood pressure is high, in the majority of cases, you won’t be able to notice any symptoms, which is why it is really important to have it checked. Having a higher blood pressure, particularly in important areas such as the coronary arteries (supplying the heart), causes a narrowing which is known as atherosclerosis (3). This can mean it is harder to get oxygen to the heart muscle which could lead to a heart attack. High blood pressure also puts you at higher risk of stroke and bleeding. 

What is normal blood pressure?

Blood pressure will vary from person to person, and can depend on your family history, your gender, your lifestyle, medications and so much more. 

It is normal for your blood pressure to measure differently at different times of the day, and also in different situations. Some people have high blood pressure when they visit healthcare professionals, and this is known as ‘white coat hypertension’.

Normal blood pressure is 120/80 mmHg. Note there is a top and a bottom number which are both important. If your blood pressure is 140/90mmHg or higher, this is defined as hypertension and would need to be acted upon (4). 

How do we measure blood pressure?

Blood pressure is measured using a machine which can be manual, and done by a doctor or nurse, but often, we use electronic blood pressure machines. These are available to buy from some pharmacies and online. If you are measuring your blood pressure at home, please ensure that you follow the instructions for the machine to ensure an accurate reading. 

You should be sat down when measuring your blood pressure, and try to be relaxed to avoid a higher reading as stress can increase your blood pressure. There is a guide on how to measure your blood pressure at home here 

A healthy individual should not have to measure their blood pressure regularly. You may be offered to have your blood pressure checked at your GP, pharmacy, workplace or during your NHS Health Check. However, if your healthcare professional has asked you to measure your blood pressure readings, this will often be in the form of a diary. In which case, measure your blood pressure three times in the morning, and the evening, leaving 1 minute between readings and recording the lowest of the three values. 

What treatments are available for high blood pressure?

High blood pressure can be prevented or controlled in some people (5), with changes to your lifestyle. This can be through reducing salt intake (recommended intake is 6 grams per day), exercise, diet, improving your sleep, reducing your caffeine and alcohol intake and quitting smoking. There are some tips on a lower salt diet here.

If you need to take medicine for blood pressure, there are several different types available. These all work in different ways, and it is important to ensure that you take medication as prescribed and take medication each day (6). 

As mentioned above, generally speaking, high blood pressure doesn’t have symptoms, so you don’t ‘feel’ unwell. So it is important to remember to take your medication regularly, as it is helpful to prevent damage to your blood vessels, particularly in your kidneys, heart, eyes and brain.


  1. British Heart Foundation. High blood pressure [Internet]. [cited 2022 Sep 6]. Available from:
  2. NHS. High blood pressure (hypertension) [Internet]. 2019 [cited 2022 Sep 6]. Available from:
  3. NHS. Causes -High blood pressure (hypertension) [Internet]. 2019 [cited 2022 Sep 5]. Available from:
  4. NHS. Diagnosis -High blood pressure (hypertension) [Internet]. 2019 [cited 2022 Sep 5]. Available from:
  5. NHS. Prevention -High blood pressure (hypertension) [Internet]. 2019 [cited 2022 Sep 4]. Available from:
  6. NHS. Treatment High blood pressure [Internet]. 2019 [cited 2022 Sep 5]. Available from:

Blood pressure – do you know your numbers? was last modified: September 7th, 2022 by Nirja Joshi

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