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25 April 2023

The Damage High Blood Pressure Can Cause

Is high blood pressure dangerous?

Have you ever wondered why, or even if, it matters that much whether someone’s blood pressure is raised? After all, if someone feels fine, it probably isn’t doing them any harm, right?

Actually, many people with high blood pressure feel perfectly well in themselves, but the raised blood pressure can be causing slow but steady damage all over the body.

Kinetik Wellbeing Upper Arm Automatic Blood Pressure Monitor Bpx2

Dr Katie BlogWritten by Dr Katie Stephens, GP

Dr Katie graduated from the University of Manchester in 2007 (MBChB) and completed her GP training in the West Midlands in 2012 (MRCGP). 


High blood pressure risks

We know that high blood pressure causes the following problems:

Cardiovascular disease

According to the WHO, hypertension (the medical term for high blood pressure) is responsible for about half of all Strokes and Heart Attacks. Strokes and heart attacks are both examples of ‘cardiovascular disease’ – meaning a problem with the heart or blood vessels.

When the blood pressure gets too high, it causes a build-up of fatty tissue inside blood vessels. This narrows the space for blood to travel through, leading to less blood flowing through it and sometimes even blocking off the flow completely. A bit like when a garden hose gets twisted and it is harder for the water to get through. Or if a three lane motorway suddenly became a single country lane – traffic would pile up. When this happens in blood vessels carrying blood away from the heart, it is called atherosclerosis. If the blood vessel that is affected is in the brain, this causes a stroke.

If it happens to a blood vessel supplying the heart itself (coronary artery), it causes a heart attack.

Enlarged heart

Raised blood pressure can cause an increase in the size of the main pumping chamber of the heart, the left ventricle (left ventricular hypertrophy). One out of every two to three people with high blood pressure get this, and it typically happens more in those whose blood pressure is more severely raised.

While usually muscular size increases sound positive, this is actually very much a negative thing. If the left ventricle grows larger, the heart becomes less efficient and coordinated in its pumping.

When it isn’t pumping as well as it should, we call this Heart Failure. This means blood isn’t getting through the heart as easily as normal, leading to something of a traffic jam of blood upstream. The heart doesn’t need to have totally stopped for us to use this term, but it is still something that needs to be taken seriously.

Heart failure can cause pooling of fluid in the legs, causing mobility issues, and in the lungs, leading to breathing difficulties.

Abnormal heart rhythms

This describes when there is an interruption to the regular ‘lub dub… lub dub’ pattern of your heart beating. The medical term for this is an arrhythmia. There are a variety of abnormal rhythms that can happen as a result of high blood pressure.

One of the more well-known ones is Atrial Fibrillationor AF. This is when the smaller two chambers at the top of the heart (the left and right atria, who normally make the ‘lub’ part of ‘lub dub’) lose their regular pace and instead beat randomly and quickly.

AF can (but doesn’t always) cause a life-threatening disruption in the way the heart beats which may cause shortness of breath, chest pain or light-headedness.

Regardless of whether this happens, it always also causes turbulent blood flow. If you imagine a smooth, steadily-flowing river that suddenly hits white-water rapids with some water rushing through quickly, and other water getting bounced off rocks, this is something like the turbulence that can happen in AF.

This turbulence increases the risk of a clot developing. If this clot then gets pushed out of the heart and gets lodged in the brain, this causes a stroke. Other types of abnormal heart rhythms, while potentially being less common, can also be life-threatening. An example of this is Ventricular Tachycardia, or VT.

Kidney Disease

The heart and the kidneys work closely together. They are able to talk to each other and make changes to how they work, to help the other out. The downside is, when there is a problem with one of them, it can cause a problem in the other.

When someone has high blood pressure, this can cause Chronic Kidney Disease (chronic meaning something that has built up over time rather than happening suddenly). Think of the kidneys a bit like a sieve. The things caught in the sieve stay in the blood, and what is let through escapes in the urine.

High blood pressure puts too much pressure on the sieve and can cause bigger holes to appear, meaning things get filtered through that shouldn’t, such as proteins. (Hence why GPs often check for protein in the urine when high blood pressure is first diagnosed.) Also, damage to the blood vessels in the kidney (atherosclerosis again!) means that they just can’t filter as well as they should, and a lot of fluid that should go in the urine actually stays in the blood.

This extra fluid in the blood vessels can make the blood pressure rise higher, causing a vicious cycle of even higher blood pressure and even greater kidney damage. If this gets particularly bad, it can be labelled as Kidney Failure.


We know that high blood pressure increases the risk of developing Dementia. It is thought that this occurs when a rise in blood pressure damages the barrier between the blood and the brain. This then leads to protein leaking into the brain, which can hurt and kill brain cells.

Eyesight Problems

The medical term for this is hypertensive retinopathy – opathy meaning ‘disease of’, retina referring to the back of the eye. If this is present, and the blood pressure isn’t treated, it can sadly lead to loss of vision ‘within a short period of time. This is why it is so important to have your eyes checked regularly if you have high blood pressure.

Erectile Dysfunction

While Erectile Dysfunction can have a variety of causes, one of the main causes is a problem with the blood supply to the penis. Raised blood pressure can damage the blood vessels here (atherosclerosis), just like elsewhere in the body, meaning less blood can get through.

Assessing and treating ED properly should therefore include checking the blood pressure and cholesterol, not just taking Viagra. (High cholesterol can also damage blood vessels.)

What high blood pressure is dangerous?

The simple answer: all high blood pressure is dangerous.

Very high blood pressure (180/120 mmHg or higher) can cause immediate problems, such as a stroke, and we would recommend seeking urgent medical attention if your blood pressure is this high and is staying this high when you recheck it. You can do this by calling the NHS on 111. If you are also feeling unwell, (e.g., if you have chest pain, ankle swelling, blurred vision, breathing problems or feel confused), you should go to A&E.

However, blood pressure doesn’t need to reach this severely high level to cause the above problems. Usually, the cut off for diagnosing someone with high blood pressure using readings taken from home is 135/85. If your blood pressure is often at this level or higher, you are probably at risk of developing the above problems.

To reduce your chance of getting these problems, an ‘ideal’ blood pressure target of 120/80 mmHg may be best, but this will depend on other things like your age and medical history. If you have other medical conditions, such as kidney disease or diabetes, your target blood pressure may be different. If this is the case and you aren’t sure what you should be aiming for, it may be helpful to talk to your GP or Practice Nurse.

For more information, please read our definitive guide blood pressure.

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