High Blood Pressure
What the numbers mean, how to measure your blood pressure properly at home, and what really works to bring it down.
High blood pressure, also called hypertension, is one of the most common long term conditions in the UK and one of the most important to get right. It rarely causes symptoms, which is why so many people do not know they have it. The good news is that it is easy to detect and very treatable.
What is high blood pressure?
Blood pressure is the force of blood pushing against the walls of your arteries as your heart pumps it around the body. It naturally rises and falls through the day with activity, stress, and sleep. High blood pressure means it stays consistently higher than it should be, which over years puts strain on the heart and damages blood vessels.
How common is it?
Around one in three adults in the UK has high blood pressure, and it is estimated that several million of them have not been diagnosed. In most cases there is no single cause. Age, family history, ethnicity, weight, salt intake, alcohol, and inactivity all contribute.
Source: British Heart Foundation.
Understanding the numbers
Blood pressure is written as two numbers, for example 128/82, measured in millimetres of mercury (mmHg).
Systolic (top number)
The pressure when your heart beats and pushes blood out. This is the higher of the two numbers.
Diastolic (bottom number)
The pressure when your heart rests between beats. This is the lower of the two numbers.
| Category | In clinic | Home average | What it means |
|---|---|---|---|
| Ideal | Below 120/80 | Below 120/80 | The range associated with the lowest risk |
| High normal | 120/80 to 139/89 | 120/80 to 134/84 | Not high, but worth keeping an eye on |
| Stage 1 hypertension | 140/90 or above | 135/85 or above | Lifestyle changes, with medication depending on overall risk |
| Stage 2 hypertension | 160/100 or above | 150/95 or above | Medication recommended alongside lifestyle changes |
| Severe | 180/120 or above | n/a | Needs prompt assessment, same day if you have symptoms |
Hypertension thresholds from NICE guideline NG136. Either number being raised is enough to count. Home thresholds are lower because readings taken at home are usually lower than those taken in a clinic.
Why it matters
High blood pressure usually causes no symptoms at all. The reason to treat it is to prevent the damage it does quietly over many years.
Heart
Heart attack, heart failure, and atrial fibrillation. The heart has to work harder against higher pressure and its muscle thickens over time.
Brain
High blood pressure is the single biggest risk factor for stroke, and it also raises the risk of vascular dementia.
Kidneys
Sustained high pressure damages the fine blood vessels that filter the blood, leading to chronic kidney disease.
Eyes
Damage to the small blood vessels at the back of the eye can affect vision.
The encouraging part: lowering blood pressure works. Large pooled analyses of trials show that each 10 mmHg reduction in systolic pressure cuts the risk of major cardiovascular events by around 20%, and the risk of stroke by around 27%.
Source: Ettehad et al, Lancet, 2016.
How it is diagnosed
A single high reading in clinic is not enough for a diagnosis. Blood pressure is often higher in a medical setting, sometimes called the white coat effect. If your clinic reading is 140/90 or above, the diagnosis should be confirmed with readings taken away from the clinic.
Ambulatory monitoring (ABPM)
A cuff worn for 24 hours that takes readings automatically through the day and night while you go about normal life. This is the most accurate method.
Home monitoring (HBPM)
You take your own readings twice a day for up to a week using a validated monitor. This is a well accepted alternative and is described in the next section.
Once high blood pressure is confirmed, we check for any effect on the body and estimate your overall cardiovascular risk. This usually involves blood tests for kidney function, cholesterol, and blood sugar, a urine test for protein, an ECG, and a look at the back of the eyes.
Measuring at home
Home readings are only useful if they are taken properly. Use an automatic upper arm monitor that has been clinically validated. The British and Irish Hypertension Society publishes a list of validated monitors. Wrist and finger devices are less reliable.
How to take a good reading:
- Avoid caffeine, smoking, and exercise for 30 minutes beforehand, and empty your bladder
- Sit quietly for five minutes with your back supported and feet flat on the floor
- Rest your arm on a table so the cuff is level with your heart
- Use the right size cuff on bare skin, not over clothing
- Do not talk or look at your phone while the reading is taken
- Take two readings, at least one minute apart, and write both down
- Do this morning and evening for at least four days, ideally seven
To work out your average, discard the readings from the first day and average all the rest. Send us the full list and we will do the calculation with you. Try not to check more often than advised. One high reading means very little, and frequent checking tends to cause anxiety, which pushes readings up.
Lifestyle changes
Lifestyle changes are recommended for everyone with high blood pressure, whether or not medication is needed. For some people they are enough by themselves, and for others they mean fewer tablets or lower doses.
Cut down on salt
Aim for no more than 6g a day, about a level teaspoon. Most salt is already in food such as bread, processed meat, ready meals, and sauces, so checking labels matters more than the salt cellar.
Lose weight if you need to
As a rough guide, blood pressure falls by around 1 mmHg for every kilogram lost. Waist size matters as well as weight.
Be active
Aim for at least 150 minutes of moderate activity a week, such as brisk walking or cycling. Regular activity typically lowers blood pressure by 4 to 9 mmHg.
Drink less alcohol
Regularly drinking above 14 units a week raises blood pressure. Cutting back often produces a noticeable drop within weeks.
Stop smoking
Smoking does not directly cause sustained high blood pressure, but together they multiply the risk of heart attack and stroke.
Watch the caffeine
Large amounts of coffee, tea, cola, and energy drinks can raise blood pressure. Moderate intake is fine for most people.
Medication
Whether medication is recommended depends on how high your blood pressure is, your age, and your overall risk of heart disease and stroke. Which medicine is suggested first depends on your age, ethnic background, and other conditions such as diabetes. Many people need two or more medicines at lower doses to reach their target, which is normal and not a sign of failure.
ACE inhibitors
Examples: ramipril, lisinopril, perindopril
Relax blood vessels. A dry tickly cough affects around one in ten people. A blood test for kidney function is needed before and one to two weeks after starting. Not used in pregnancy.
Angiotensin receptor blockers (ARBs)
Examples: losartan, candesartan
Work in a similar way to ACE inhibitors and are often used when an ACE inhibitor causes a cough. The same blood tests are needed. Not used in pregnancy.
Calcium channel blockers
Examples: amlodipine, felodipine
Widen the arteries. Ankle swelling is the commonest side effect, along with flushing and headache in the first few days.
Thiazide like diuretics
Examples: indapamide
Help the kidneys remove salt and water. They can lower potassium and sodium and raise uric acid, so occasional blood tests are needed.
Treatment targets
For most adults under 80, the aim is a clinic reading below 140/90, or a home average below 135/85. For people aged 80 and over, the target is a clinic reading below 150/90, or a home average below 145/85. Some people with other conditions are given a lower individual target.
Worth knowing: Blood pressure tablets work only while you take them, and treatment is usually long term. Do not stop without discussing it first. If you feel dizzy or faint when standing, tell us, as your dose may need adjusting. If you are planning a pregnancy, speak to us before you conceive, because some of these medicines need to be changed.
When to get urgent help
Call 999 or go to A&E if you have a very high reading (180/120 or above) together with any of the following:
- Chest pain or tightness
- Severe shortness of breath
- A sudden, severe headache
- Blurred vision or sudden loss of vision
- Confusion or drowsiness
- Weakness or numbness of the face, arm, or leg, or difficulty speaking
If your reading is 180/120 or above and you feel well, sit quietly for five minutes and repeat it. If it is still that high, contact us or NHS 111 the same day for advice.
Common questions
Short answers to the questions we are asked most often.
What counts as high blood pressure?
In the UK, high blood pressure is a clinic reading of 140/90 mmHg or above, confirmed by an average of 135/85 or above on home or 24 hour monitoring. An ideal blood pressure is below 120/80. Either number being raised is enough to count.
How do I measure my blood pressure at home properly?
Use a validated upper arm monitor. Sit quietly for five minutes with your back supported, feet flat, and your arm resting at heart level. Take two readings at least one minute apart, morning and evening, for four to seven days. Discard the first day and average the rest.
Does high blood pressure cause symptoms?
Usually not. Most people with high blood pressure feel completely well, which is why so many cases go undiagnosed. The reason to treat it is to prevent the damage it does over years to the heart, brain, kidneys, and eyes.
Can I lower my blood pressure without medication?
Often, yes. Cutting salt to no more than 6g a day, losing excess weight, being active for at least 150 minutes a week, and drinking less alcohol all lower blood pressure. For some people these changes are enough, and for others they mean fewer tablets or lower doses.
When is high blood pressure an emergency?
Call 999 or go to A&E if you have a reading of 180/120 or above together with chest pain, severe breathlessness, a sudden severe headache, visual disturbance, confusion, or weakness of the face, arm, or leg. If you feel well, rest for five minutes, repeat it, and seek same day advice if it is still that high.
Next steps
All adults over 40 are advised to have their blood pressure checked at least every five years, and more often if it has been borderline. If you have had a high reading, or would like a proper assessment, please get in touch.