High Blood Pressure (Hypertension) Causes

Dr Kathryn Basford

Medically reviewed by

Dr Kathryn Basford

Last reviewed: 10 Jun 2019

Man at risk of the causes of high blood pressure having his blood pressure check manually by a doctor

Key takeaways

  • High blood pressure is when your blood vessels are under more strain from the blood flowing through them

  • Abnormally high blood pressure is a real problem that can lead to heart attack and stroke

  • 90 to 95% of cases of hypertension can be caused by a number of factors, such as lifestyle, diet, age, gender, ethnicity and genetic disposition

  • If you have been diagnosed with high blood pressure, you can order a repeat prescription for your medication through our online doctors

The causes of hypertension vary between patients and can be difficult to be sure of. Narrow, stiff, or clogged arteries cause higher blood pressure.

In more than 90% of patients, it’s very difficult to determine one clear cause of hypertension, and most doctors think there are a variety of issues involved.

It’s important that you get a medical check-up so your doctor can try to find out the reasons for your high blood pressure.

If you’ve been diagnosed with high blood pressure and have been taking treatment for a while, you can order a repeat prescription for your medication online. Our doctors can prescribe most UK brands, including Diovan, Aprovel, and Amias. We’ll send you a 3-month course through our pharmacy.

What causes high blood pressure?

Blood pressure is the result of the amount of blood pumped through your body by the heart and your arteries' resistance to the blood flow.

High blood pressure occurs when your blood vessels have more strain put on them from the blood flowing through them. This can be because the arteries are less flexible, and it means that your heart has to work harder to pump the blood around your body.

High blood pressure takes many years to develop, and usually causes no symptoms at all. Most people will discover they have it when they go for a medical check-up. In some cases it isn’t picked up until it causes problems like erectile dysfunction, or even a heart attack or stroke.

As we get older, our arteries become stiffer and less flexible, so an increase in blood pressure is normal over the years. But, abnormally high blood pressure is a real problem that can lead to heart attack and stroke. Over time, the excessive pressure on the walls of your arteries will cause damage to the arteries.

It’s very quick and easy to diagnose hypertension. After that, you need to work with your GP, who’ll develop a treatment plan for you.

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Essential (or primary) hypertension

The most common form of high blood pressure is called essential hypertension. It leads to about 90 to 95% of cases of hypertension and doctors usually cannot identify the exact reason for high blood pressure of this type. It’s assumed that a number of factors contribute to hypertension.

These factors include:

  • the lifestyle you have, including how much you exercise, your diet, and whether you smoke
  • stress
  • obesity
  • age
  • gender – men are more at risk than women
  • ethnicity
  • family background (genetic disposition) – whether other people in your family have had hypertension
  • high cholesterol
  • Diabetes
  • kidney disease

There’s more detail on these lower down this page, in the section called “High blood pressure risk factors”.

Essential hypertension develops slowly over years, which is why it’s symptomless most of the time – until it’s picked up on a routine check up or something triggers a heart attack, stroke, or another condition.

Secondary hypertension

The second most common cause of high blood pressure is called secondary hypertension. It represents 5-10% of cases of hypertension and is caused by an underlying condition.

Possible causes of secondary hypertension include: kidney disease, hormonal disease (e.g. gland tumour, hyperthyroidism), lead poisoning, head injuries and pregnancy.

Many of these causes of secondary hypertension are temporary and/or curable. Some medications and drugs can also cause secondary hypertension. These include antidepressants, cocaine, amphetamines, NSAID (non-steroidal anti-inflammatory drugs such as aspirin or ibuprofen in high quantities), decongestants, etc.

Less common causes

Isolated systolic hypertension is a much less common type of hypertension. It happens, when only the first number of your blood pressure is too high, for example 140mmHg in 140/80mmHg (read 140 over 80).

This number represents the systolic blood pressure (when blood is pumped into the vessels), as opposed to the diastolic blood pressure (the second number, when the heart is at rest).

This disease causes high blood pressure only when the heart is pumping blood, after which the blood pressure goes back to normal. This creates a huge chronic difference in blood pressure, which swings up and down putting great strain on your arteries.

Causes of isolated systolic hypertension (or ISH) include advanced age, anaemia (lack of red blood cells), thyroid hormone diseases and heart conditions.

Another reason for high blood pressure – called white-coat hypertension – is not as serious as the other types and happens because of the stress of being in a hospital or clinic and receiving treatment there. It is not really a case of high blood pressure as a condition but is simply a case of increased blood pressure due to stress.

This can lead to misdiagnosis, so try to relax as much as possible when in hospital or with your doctor. Sometimes your doctor will recommend that you take blood pressure readings at home with a monitor to try to judge what your readings would be in your normal situation.

High blood pressure risk factors

Lifestyle-related risk factors:

  • Smoking raises your blood pressure, and most importantly it damages your arteries in the long run
  • Lack of exercise: the arteries will lose the ability to adapt to changes in blood flow (by expanding or narrowing), thus leading to earlier aging and hardening of your arteries
  • Obesity: as your weight increases, you need more blood to “feed” your tissues in oxygen and nutrients. This means that your arteries are gradually transporting much more blood than they were originally “designed” for
  • Stress may trigger stroke and heart attack as it can temporarily lead to huge increases in blood pressure
  • Unhealthy diet: too much alcohol, salt, coffee as well as lack of potassium and vitamin D will contribute to an increase in blood pressure. Binge drinking also damages the heart

Other relevant factors include:

  • Age: the older you get the higher your blood pressure is because of the natural hardening of the arteries
  • Family background: there is a genetic aspect to hypertension which is often inherited
  • Ethnicity: some ethnic groups are more at risk of high blood pressure than others, for example people from South Asian (e.g. India) and Caribbean origins

And finally the disease-related risk factors:

  • High cholesterol, which narrows your blood vessels
  • Diabetes: 30% of people with type 1 diabetes and 50% of those with type 2 will develop high blood pressure over time
  • Kidney disease

There is a whole range of other diseases that can contribute to high blood pressure. You should also know, that risk factors usually add up, meaning that the more risk factors you accumulate (for example in the case of a 65 year old overweight, smoker with diabetes), the higher your risk of high blood pressure, heart attack or cardiovascular disease (i.e. heart and blood vessels disease).

How common is high blood pressure in the UK ?

Statistics in January 2017 showed that high blood pressure affects more than 1 in 4 adults in England. At least 50% of all heart attacks and strokes are related to high blood pressure.

But there are a lot of people who have high blood pressure without knowing it. More than 5.5 million people in England have undiagnosed high blood pressure, meaning that they are at risk of stroke, heart attack, or erectile dysfunction, but are not getting treatment.

Measuring blood pressure

The threshold that determines who has hypertension, and who hasn’t, is a blood pressure reading equal to or over 140 over 90 (140/90). The higher the blood pressure is, the greater the risk of developing other serious conditions.

If you worry you might be at risk, get into the habit of having your blood pressure checked regularly. If you know that you’re at risk (e.g. diabetes, age over 65, mild hypertension) you need to get your blood pressure measured at least once every year.

Medically reviewed by:
Dr Kathryn Basford

Dr Kathryn Basford is a qualified GP who works as a GP in London, as well as with ZAVA. She graduated from the University of Manchester and completed her GP training through Whipps Cross Hospital in London.

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Last reviewed: 10 Jun 2019

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