Causes of high blood pressure

High blood pressure or hypertension is known as the ‘silent killer’ because it rarely presents with any symptoms. It is the largest single known risk factor for heart failure, coronary heart disease and stroke. In 2015 government report, high blood pressure was responsible for 10.7 million deaths worldwide. By 2025, it is projected to affect more than 1.5 billion people around the world.

How to tell if you have hypertension

You can identify blood pressure by using a blood pressure monitor to take readings. The readings are written as one number over another.  The number on the top represents systolic blood pressure -the highest pressure in blood vessels when the heart contracts. The bottom number represents diastolic blood pressure – the lowest pressure in blood vessels in between heartbeats when the heart muscles are relaxed. 

Normal blood pressure is between 90/60mmHg and 120/80mmHg. 

According to the National Institute of Clinical Excellence high blood pressure is defined as a clinic reading of 140/90mmHg or a non-clinic average reading of 135/85mmHg [R]. Anywhere between 120/80mmHg and 140/90mmHg is generally considered to be high.

Causes and Risk Factors

High blood pressure is caused by various risk factors individually or combined that causes the artery walls to thicken and work harder to transport blood around the body. Below are direct or indirect risk factors that cause hypertension:


Naturally, as you age, you are exposed to more risk factors throughout your life. Therefore, your blood pressure increases as you get older.


People of African Carribean descent have a higher risk of high blood pressure. Although there isn’t concrete evidence to suggest why there are possible connections to lifestyle and genetics. African Carribean people also respond differently to blood pressure medication e.g. Ace inhibitors [R].

People of South Asian descent (India, Pakistan, Bangladesh, and Sri Lanka) are genetically predisposed to diabetes. This indirectly links to high blood pressure. It is recorded that 80% of people with Type 2 diabetes have high blood pressure [R].

Family history

If several members of your family have hypertension, you are genetically more at risk of developing it yourself.


Excess salt affects the sodium balance in the body which prevents the kidneys to eliminate fluid. The resultant fluid retention creates heightened pressure in the blood so the blood vessels have to work harder.

Most of the salt we consume (about 80%) is hidden in processed foods like bread, biscuits and breakfast cereals, ready meals and takeaways [R]. Always check the labels and notice that salt and sodium are sometimes interchanged on the packaging. The maximum recommendations are:

1 to 3 years – 2g salt a day (0.8g sodium)

4 to 6 years – 3g salt a day (1.2g sodium)

7 to 10 years – 5g salt a day (2g sodium)

11 years+ and adults – 6g salt a day (2.4g sodium) [R]

Too little potassium in your diet

Potassium balances the sodium levels in the body. Too little potassium will build up sodium and cause water retention. Foods high in potassium include bananas, sweet potato, spinach and apricots.


When you are overweight or obese, more blood supply is needed to reach the extra body tissue. This exerts pressure on the blood vessel walls to work harder.

Dietary cholesterol

Cholesterol clogs your arteries and causes them to narrow. Cholesterol also leads to weight gain. Both of these increase blood pressure.


Heavy drinking over time can damage the heart and in turn, can increase your blood pressure. In addition, alcohol is full of calories and causes weight gain. The maximum alcohol intake limit is 14 units a week for both men and women [R].


Chemicals in tobacco damage the lining of the arteries and cause them to narrow. Not only does this increase the blood pressure but also increases the risk of heart disease.

Lack of Exercise

People who are not physically active have higher heart rates. This means your heart pumps quicker and harder which is extra pressure on the arteries to supply the blood around the body. Lack of exercise also increases the risk of being overweight or obese.

Mental health

Stress and anxiety trigger release of cortisol and adrenaline which speeds up heart rate and increases blood pressure.


Prescribed medications that increase blood pressure include antidepressants, the contraceptive pill, steroid tablets and specific anti-inflammatory medications. Non-prescribed medication includes over the counter decongestants.

Medical Conditions

Naturally, water retention affects blood pressure so any medical conditions related to the kidney generally increases your blood pressure. 

Diabetes increases blood pressure but there is little evidence to understand why. It is theorised that obesity, a diet high in fat and sodium, inactivity and chronic inflammation all play a role. 

Conditions with hormone imbalances can increase blood pressure. An example of this is hyperthyroidism. Too much thyroid is released in the body which increases the heart rate and as a result increases the blood pressure too.


Factors such as extra weight, inactivity, age and family history can all contribute to pregnancy-induced high blood pressure. If you already have high blood pressure from before, it could spike your blood pressure even more.


NHS. (2019).Causes- high blood pressure. Available:

Blood Pressure UK. (2019). What is high blood pressure? Available:

NICE. (2011). Diagnosing hypertension. Available:

Public Health England. (2017). Health matters: combating high blood pressure. Available: