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Medical Terms Explained: Blood Pressure

Around 38% of the UK population live with high blood pressure (hypertension). Hypertension is publicized as the “silent killer” for its absence of symptoms. It is one of the biggest risk factors for premature death and disability in England. New figures from PHE show that over 5 million people are unaware they have high blood pressure as the condition can easily go unnoticed until a serious medical problem appears sometimes years later.  In order to keep high blood pressure under control, it is important to know what levels are considered normal, as well as how to tell when your blood pressure is too high. Understanding blood pressure however, isn’t easy especially when you are confronted with words like “systolic” and “diastolic”. We have produced a friendly guide, explaining the basic but fundamental concepts.

What is blood pressure?

Blood pressure is the force of circulating blood against the inner walls of your blood vessels. The pressure of circulating blood is determined by three forces;

  • How much blood your heart is pumping
  • How forcefully your heart is pumping
  • The amount of resistance to blood flow in your arteries

Blood pressure can vary according to an individual’s lifestyle, general health and genetics. Low blood pressure is called hypotension and blood pressure that is consistently high is called hypertension.

Measurement: What do the numbers mean?

Blood pressure explanation

Blood pressure is measured with a blood pressure cuff called a syphygmomanometer. It is an inflatable cuff that is usually wrapped around your upper arm. The cuff is inflated to above what the health professional knows to be your systolic pressure; they will then use a stethoscope to read your blood pressure as the cuff deflates.

Blood pressure is generally expressed as two numbers, similar to a fraction, with one number on top and one on the bottom; The top number represents the pressure when your heart contracts; this is called systolic pressure. The bottom number represents the pressure when your heart rests between beats; this is called diastolic pressure.

Your healthcare provider will read this blood pressure as “120 over 80”.   Blood pressure readings are expressed as “millimetres of mercury” which is abbreviated as “mm Hg.”

What’s normal?

Normal blood pressure is considered to be 120 systolic and 80 diastolic, written as 120/80 mm Hg. At this optimal level there is a reduced risk of heart disease and stroke. If you have a blood pressure reading between 120/80 to 140/90 it is classified as “prehypertension”. Although these numbers are not classified as high you have moved out of the normal range. The higher the reading the higher the risk of health problems and you should take steps to reduce a rise above the optimal level.  

Hypertension diagnosis

You are likely to be diagnosed with stage 1 hypertension is your blood pressure reading remains between 140/90 mm Hg to 159/99 mm Hg over a period of time.

If your blood pressure reading shows a systolic reading of 160 or more, or a diastolic reading of 100 or more, then this is considered stage 2 hypertension, a more serious condition that may require one or more medications to keep under control

Any reading above 180 systolic or 120 diastolic is a hypertensive emergency and medical help must be sought immediately.

The risk factors for developing hypertension include:

  • Obesity
  • Smoking
  • Excess Alcohol consumption
  • Sedentary lifestyle
  • High cholesterol
  • Eating too much salt
  • Stress

Primary or essential hypertension accounts for 90-95% of all cases and doesn’t have a specific medical cause, so we can influence blood pressure by our lifestyle choices. There is however risk factors that cannot be managed:

  • The risk of hypertension increases with age
  • High blood pressure can run in families

Proactive reactive decision

Why worry if you feel ok?

If left untreated high blood pressure can cause a hardening of the arteries, whereby they become thicker, stiffer and narrower. The complications of this are many and can be very serious:

  • Uncontrolled hypertension is one of the major risk factors for heart disease.
  • A greatly increased risk of stroke
  • An enlarged heart that can lead to congestive heart failure
  • Kidney disease
  • Vision damage from blurred vision to blindness


Managing blood pressure is a choice; you choose to get your blood pressure checked on a regular basis this can be at a drop in clinic, with your GP or at work if your employer provides voluntary health screening; you choose to adopt and maintain a healthy lifestyle. Moving in the right direction doesn’t have to be drastic if you start early enough.

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