High Blood Pressure (Hypertension)
What it is, how it develops, and why measuring at home can make a real difference.
UPDATED: 10 February 2026
High blood pressure — also known as hypertension — is a common condition where the pressure inside the arteries stays higher than it should, most of the time.
Many people look for high blood pressure symptoms, but in reality, it often causes no noticeable symptoms at all, which is why it can go undetected for years. Many people carry on as normal without headaches, dizziness, or warning signs. That’s why you’ll sometimes hear it described as a “silent” issue, not because it’s rare or mysterious, but because it can quietly raise the risk of serious problems over time if it goes unnoticed or unmanaged.
Before we talk about how high blood pressure develops (and what it can do), it helps to understand a simple question:
What do we actually mean by “blood pressure”?
What is blood pressure?
Every time your heart beats, it pushes blood into your arteries. That push creates a wave of pressure inside the blood vessels — a little like turning on a tap that’s already connected to a hose full of water.
That pressure isn’t constant. It rises and falls with every heartbeat, all day and night.
Two phases of each heartbeat
There are two main phases to each heartbeat:
Systole – this is when the heart contracts (squeezes) and pumps blood out. The pressure in the arteries rises and reaches its highest point, called systolic blood pressure.
Diastole – this is when the heart relaxes and refills with blood, ready for the next beat. During this phase, the pressure in the arteries drops back down to its resting level, called diastolic blood pressure.
Video showing blood flow through the heart. Blood fills the atria (upper chambers) before flowing into the ventricles (lower chambers). The ventricles then contract, pumping blood out of the heart.
Why arteries can handle this (most of the time)
Arteries aren’t rigid pipes. Their walls are designed to stretch and spring back with each pressure wave. They contain layers of elastic fibres, which allow them to expand during systole and recoil during diastole.
That flexibility helps keep blood flow smooth and steady as it travels into smaller blood vessels supplying your brain, organs, muscles, and other tissues.
Video showing blood flow through an artery - notice how the artery expands and contracts during systole and diastole.
Why blood pressure often rises with age
As we get older, those elastic fibres in the artery walls can gradually lose some of their flexibility. The arteries don’t expand quite as easily as they used to.
When arteries become stiffer, the heart has to generate more pressure to move blood forward with each beat. Over time, that can contribute to a gradual rise in both systolic and diastolic blood pressure.
This age-related stiffening doesn’t mean high blood pressure is inevitable — but it does mean the arteries are less forgiving when pressure rises for other reasons.
Rising blood pressure isn’t usually caused by a single event. More often, it develops when the arteries are exposed to repeated strain over time, particularly when pressure remains elevated day after day.
When blood pressure remains higher than it should be, day after day, the inner lining of the arteries is exposed to increased force. Over time, this constant pressure can cause tiny areas of damage along the artery walls.
The body responds to this damage in the same way it responds to injury elsewhere: by trying to repair it.
How can high blood pressure develop?
When repair turns into a problem
The trouble begins when this repair process becomes ongoing.
At these damaged sites, the artery wall becomes inflamed. Healing cells, including white blood cells, gather to repair the area. At the same time, fats and cholesterol circulating in the blood can begin to stick to these irritated patches.
Slowly, layer by layer, a fatty deposit builds up within the artery wall. This process is known as atherosclerosis.
As these plaques grow, the inner surface of the artery becomes thicker and less smooth. The space available for blood to flow through narrows, and the artery becomes stiffer.
Video showing the gradual build up of plaque within the artery wall. This narrows the blood vessel restricting blood flow and forces the heart to work harder, leading to higher blood pressure.
A vicious cycle inside the arteries
Once this process is underway, it can begin to feed on itself.
As arteries narrow and stiffen, the heart has to work harder to push blood through them. To overcome this resistance, it generates even more pressure.
That extra pressure can cause further damage to artery walls, accelerating plaque build-up, which then increases blood pressure even more.
This creates a feedback loop that none of us wants:
Higher blood pressure → artery wall strain → damage & inflammation → plaque builds up → arteries narrow & stiffen → blood pressure rises further
Worth knowing:
Atherosclerosis doesn’t happen overnight — it can develop quietly over many years, often without causing noticeable symptoms.
When plaques become dangerous
Over many years, atherosclerotic plaques may simply narrow arteries — but problems arise when they become unstable.
If the surface of a plaque ruptures, the body treats it like a wound. A blood clot forms over the rupture site. If that clot grows large enough, it can severely restrict — or completely block — blood flow through the artery.
Where that blockage occurs determines the consequences.
Long-standing high blood pressure often affects the body gradually and silently, meaning damage can develop long before symptoms appear.
When high blood pressure and atherosclerosis progress together, the risk of sudden, serious events increases.
How high blood pressure affects the body
Heart attack:
If a clot blocks one of the coronary arteries supplying an area of heart muscle, oxygen can’t then reach that area. The affected heart muscle begins to suffer damage — this is a heart attack.
Ischaemic stroke:
If a clot blocks blood flow to part of the brain, brain cells are starved of oxygen. This is known as an ischaemic stroke and can lead to long-term disability or, in severe cases, death.
Haemorrhagic stroke:
Long-standing high blood pressure can also weaken blood vessel walls in the brain. In some cases, a vessel may rupture, causing bleeding into or around the brain. This is known as a haemorrhagic stroke and can be life-threatening.
Act early:
The earlier raised blood pressure is noticed, the more opportunity there is to protect the heart, brain, kidneys, and eyes.
It’s not only heart attacks and strokes.
When blood pressure stays high for years, it can quietly strain and damage other parts of the body too. For example:
The heart muscle can thicken to cope with the extra workload (often called left ventricular hypertrophy).
The heart can eventually weaken, leading to symptoms of heart failure such as breathlessness and reduced exercise tolerance.
The kidneys can be damaged, because they rely on tiny, delicate blood vessels to filter the blood.
The brain’s small vessels can be affected, which is one reason long-term high blood pressure is linked with vascular cognitive decline.
The eyes can be affected, as high pressure can damage the small blood vessels that supply the retina, leading to vision problems.
How blood pressure is measured
By this point, it’s clear why blood pressure matters. The next question is more practical:
How do we actually measure it?
When blood pressure is checked, the result is given as two numbers, usually written one above the other — for example, 120/80 mmHg.
These numbers reflect the two phases of each heartbeat you’ve already learned about:
The top number is your systolic blood pressure — the pressure in your arteries when the heart squeezes and pushes blood out.
The bottom number is your diastolic blood pressure — the pressure when the heart relaxes between beats.
The unit used, mmHg (millimetres of mercury), comes from early pressure-measuring devices and is still used today worldwide.
Why one reading is rarely enough
Blood pressure isn’t a “score”. It’s a snapshot that can change with stress, movement, meals, and how relaxed you feel.
This is completely normal — just as your heart rate rises when you walk and falls when you rest.
For this reason, doctors usually place the most weight on blood pressure readings taken at rest, in calm conditions, rather than a single reading taken in a rushed or unfamiliar setting.
Interesting fact:
Simply talking during a blood pressure check can raise the reading — which is why quiet, relaxed conditions matter.
Why measurement over time matters more than a single number
A single blood pressure reading can be misleading. It may be higher than usual because you’re anxious, in pain, or distracted. Or it may be lower than usual if you’re unusually relaxed.
What really helps build an accurate picture is a pattern.
Repeated measurements taken under similar conditions — especially when you’re relaxed — allow trends to emerge. These trends are far more useful than any one-off result when it comes to understanding whether blood pressure is genuinely raised over time.
This is why medical guidelines increasingly support measuring blood pressure outside the clinic, in everyday settings where people feel more at ease. 1,2,3,4
Seeing blood pressure over time helps turn numbers into something meaningful. Instead of reacting to a single reading, you begin to understand how your blood pressure behaves day to day — which is why regular, consistent measurement is so valuable.
Why measuring blood pressure at home makes sense
Many people are surprised to learn that blood pressure measured at home is often more representative of true resting blood pressure than readings taken in a medical setting.
At home, you’re more likely to be seated comfortably, unrushed, and relaxed. Over time, repeated readings taken in this environment can provide a clearer, more consistent picture of what your blood pressure is really doing day to day.
Medical guidelines generally consider a normal home blood pressure to be below 135/85 mmHg. 2,3,4 However, interpretation of readings depends on individual circumstances and professional medical advice.
Seeing blood pressure outside a clinical setting can also explain why readings sometimes appear higher at appointments. Many people experience what’s known as white coat hypertension, where blood pressure rises temporarily due to anxiety or unfamiliar surroundings.
Regular home readings provide useful context, helping distinguish between occasional spikes and consistently raised blood pressure — and making conversations with a doctor more informed, grounded in real information rather than isolated readings.
For many people, this naturally leads to questions about home monitoring. If you’d like to explore this in more detail, our guide to Blood Pressure Monitors explains how home monitoring works in practice and what to consider when choosing a device.
Checking your blood pressure at home
By now, it should be clear why blood pressure matters — and why it often goes unnoticed.
The reassuring part is that blood pressure is measurable. You don’t need to wait for symptoms, and you don’t need medical training to begin understanding what your numbers are doing over time.
For many people, checking blood pressure at home becomes a simple routine. When measurements are taken calmly, in familiar surroundings, they often provide a clearer picture of true resting blood pressure than occasional readings taken elsewhere.
What matters most is consistency — using the same approach each time, and looking for patterns rather than reacting to a single number.
Home blood pressure monitors
Modern home blood pressure monitors make this process straightforward. Many are designed for ease of use, clear displays, and simple record-keeping. But not all monitors are created equal, and choosing one can feel confusing when faced with hundreds of options.
Understanding what to look for in a monitor — for accurate, meaningful readings at home — and how to use it correctly, is the next step.
Key Takeaways: High blood pressure and long-term health
High blood pressure often develops gradually and causes no noticeable symptoms.
Over time, persistently raised pressure can damage blood vessels and strain vital organs.
Single readings can be misleading — patterns over time give a clearer picture.
Measuring blood pressure at home helps turn uncertainty into understanding and supports earlier action.
When to seek medical help
This content is for general education and does not interpret individual readings or provide medical advice.
If you’re concerned about your blood pressure or feel unwell, contact your doctor or a qualified healthcare professional.
National health organisations provide guidance on when medical attention may be needed:
NHS: High blood pressure
If you feel acutely unwell, seek urgent medical help.
Continue to our guide on Blood Pressure Monitors to learn how home monitoring works in practice, and what to consider when choosing a device.
This page is part of a series designed to help you better understand your heart and blood pressure.
Important Information:
This page is provided for general educational purposes only and does not constitute medical advice. Medical knowledge and guidance evolve over time, and information may change. Always seek advice from a qualified healthcare professional regarding personal health concerns or medical decisions.
For more details, please see our full Disclaimer.
References
1. M, Stergiou GS, Tomaszewski M, Wainford RD, Williams B, Schutte AE. 2020 International Society of Hypertension Global Hypertension Practice Guidelines. Hypertension. 2020 75(6):1334-1357.
2. Williams B, Mancia G, Spiering W, Agabiti Rosei E, Azizi M, Burnier M, Clement DL, Coca A, de Simone G, Dominiczak A, Kahan T, Mahfoud F, Redon J, Ruilope L, Zanchetti A, Kerins M, Kjeldsen SE, Kreutz R, Laurent S, Lip GYH, McManus R, Narkiewicz K, Ruschitzka F, Schmieder RE, Shlyakhto E, Tsioufis C, Aboyans V, Desormais I; ESC Scientific Document Group. 2018 ESC/ESH Guidelines for the management of arterial hypertension. Eur Heart J. 2018 1;39(33):3021-3104.
3. Stergiou GS, Palatini P, Parati G, O'Brien E, Januszewicz A, Lurbe E, Persu A, Mancia G, Kreutz R; European Society of Hypertension Council and the European Society of Hypertension Working Group on Blood Pressure Monitoring and Cardiovascular Variability. 2021 European Society of Hypertension practice guidelines for office and out-of-office blood pressure measurement. J Hypertens. 2021 Mar 11.
4. Jones NR, McCormack T, Constanti M, McManus RJ. Diagnosis and management of hypertension in adults: NICE guideline update 2019.