High Blood Pressure

Key points

What it is

Blood pressure is the force of blood against the artery walls, written as two numbers: the pressure as the heart beats (systolic) over the pressure between beats (diastolic). It is measured in millimetres of mercury (mmHg). Blood pressure varies all day, rising with activity, stress, pain and caffeine, so a single high reading does not make a diagnosis.

Hypertension means blood pressure that stays high. In the UK, NICE defines it as a clinic reading of 140/90 mmHg or higher together with an average of 135/85 mmHg or higher on home or 24-hour (ambulatory) monitoring.¹ It is graded by how high it is: stage 1 (clinic 140/90 to 159/99), stage 2 (160/100 or higher) and stage 3 or severe (180/120 or higher).¹ "Essential" or "primary" hypertension means no single underlying disease is responsible, which is the case for more than nine in ten people. A small number have a secondary cause, such as a kidney, hormone or blood vessel problem, which is looked for in younger people and when the pattern is unusual.¹

It is very common, especially with age, and many people who have it do not know.²

What causes it, and who is at risk

Blood pressure is set by how much fluid is in the circulation, how hard the heart pumps, and how tight the small arteries are. The kidneys control the first by deciding how much salt and water to keep. The nervous system and hormones such as adrenaline, angiotensin and aldosterone control the rest.

For most people the roots are metabolic. Insulin resistance, where the body’s cells respond less well to insulin and insulin levels run high, is closely tied to high blood pressure, and it has been found even in slim people with normal blood sugar.⁴ On the outside it usually shows as extra weight around the middle, and one leading review estimates that excess weight accounts for 65 to 75% of the risk of essential hypertension.³ The weight is best understood as the visible sign of the metabolic disturbance underneath, rather than the whole story. Signals from excess fat inside the abdomen, and possibly the high insulin levels themselves, switch on the system that retains salt (the renin-angiotensin-aldosterone system) and increase the activity of the sympathetic (fight-flight) nervous system. The kidneys then hold on to more salt and water, and blood pressure rises.^3,7 The metabolic health perspective below explains this further.

Other risk factors include age, a family history of high blood pressure, Black African, Black Caribbean or South Asian family background, drinking too much alcohol, smoking and long-term stress,² and lack of sleep. Some medicines can raise blood pressure, including anti-inflammatory painkillers, some decongestants, the combined contraceptive pill, steroids and some antidepressants. Sleep apnoea, which is common with obesity, raises blood pressure and is worth asking about if you snore heavily or wake unrefreshed.

Symptoms and signs

High blood pressure usually causes no symptoms at all, which is why it is called a silent condition. Rarely, when very high, it can cause headaches, blurred vision or chest pain.² Most people find out at a routine check, at the pharmacy, or when being seen for something else. The only way to know is to measure it.²

How it is diagnosed

If a clinic reading is 140/90 or higher, the reading is repeated, and 24-hour ambulatory monitoring is offered to confirm the diagnosis, or home monitoring if that is unsuitable.¹ For home monitoring, NICE asks for two readings a minute apart, morning and evening, for at least four and ideally seven days, discarding the first day and averaging the rest.¹ Hypertension is confirmed when the clinic reading is 140/90 or higher and the home or daytime ambulatory average is 135/85 or higher.¹ Home and ambulatory readings run about 5 mmHg lower than clinic readings, which is why the two thresholds differ.¹ Some people have a white-coat effect (high only in the clinic) and some have masked hypertension (normal in the clinic, high at home); monitoring away from the clinic picks up both.¹

At diagnosis, NICE recommends checks for damage already done and for other risk factors: a urine test for protein, blood tests for HbA1c, kidney function and cholesterol, an eye examination and an ECG.¹ HbA1c matters here because high blood pressure and type 2 diabetes so often arrive together. Your clinician will also estimate your overall 10-year risk of heart attack and stroke (in the UK, with the QRISK tool), because the decision to treat depends on the whole picture, not the blood pressure alone.¹

A reading of 180/120 or higher needs urgent assessment, with prompt checks for organ damage and a repeat reading within seven days if none is found. If there are symptoms such as chest pain, new confusion, breathlessness or sudden kidney problems, or signs of damage at the back of the eye, same-day specialist assessment is needed.¹

The metabolic health perspective

High blood pressure rarely arrives alone. It travels with a larger waist, raised triglycerides, low HDL cholesterol, fatty liver, prediabetes and type 2 diabetes, the cluster that signals insulin resistance. In 1987 a small study found that people with essential hypertension were insulin resistant even when they were slim and had normal blood sugar, and that the more insulin resistant they were, the higher their blood pressure.⁴

How insulin resistance raises blood pressure is still debated. High insulin levels can make the kidneys retain sodium and can stimulate the sympathetic (fight-flight) nervous system, both of which push pressure up, though some researchers argue that other consequences of excess fat, such as activation of the salt-retaining hormone system and signals from fat tissue, do most of the work.^3,7 Either way the conclusion for the person with high blood pressure is the same: the fat inside the abdomen, the high insulin and the raised blood pressure are one process, not three separate problems. The metabolic consequences of insulin resistance, such as high blood sugar and abnormal blood fats, combine with high blood pressure to damage the arteries and kidneys faster than either would alone.⁷

Improving metabolic health usually lowers blood pressure. When insulin resistance improves, blood pressure usually falls with it, alongside weight, waist, triglycerides and blood sugar.^5,6

Treatment and management

The aim is to bring blood pressure below the target for your age and keep it there, because that is what lowers the risk of stroke, heart attack, heart failure, kidney disease and dementia.^1,2 Even a small reduction helps.² Lifestyle change is offered to everyone with raised or high blood pressure, whether or not medicines are started.¹

When medicines are recommended

NICE recommends offering medicines, alongside lifestyle change, to anyone with persistent stage 2 hypertension (clinic 160/100 or higher), and discussing them with people under 80 with stage 1 hypertension who also have organ damage, cardiovascular disease, kidney disease, diabetes, or a 10-year cardiovascular risk of 10% or more.¹ For people under 60 with stage 1 hypertension and a risk score below 10%, NICE says to consider medicines, bearing in mind that a 10-year score may underestimate lifetime risk.¹ For people over 80 with stage 1 hypertension, medicines are considered if the clinic reading is over 150/90.¹ Within these rules there is room for choice: NICE asks clinicians to discuss the risks and benefits, including the option of no medicines, and to keep supporting lifestyle change either way.¹ Someone with stage 1 hypertension and no other risk factors can reasonably agree a period of concentrated lifestyle change with repeat readings before deciding.

Targets

For adults under 80, the clinic target is below 140/90 mmHg (home average below 135/85). For adults 80 and over it is below 150/90 (home below 145/85).¹ People with chronic kidney disease and a heavy protein leak have a lower target of 130/80.¹ A large American trial found that aiming for a systolic pressure under 120 rather than under 140 prevented more heart attacks, strokes and deaths in people at high cardiovascular risk without diabetes, at the cost of more fainting, kidney and salt-balance side effects, which is why some clinicians aim lower in selected people.⁸

Lifestyle and the Health Foundations

Nutrition

A diet change that reduces insulin, waist size and weight lowers blood pressure. Reducing sugar, refined carbohydrate and ultra-processed food, building meals on protein and non-starchy vegetables, and reducing or personalising starchy carbohydrate does this directly. In trials of lower-carbohydrate eating, systolic blood pressure fell by around 5 mmHg alongside falls in weight, triglycerides, blood sugar and insulin,⁵ and in a two-year UK general practice study of people with type 2 diabetes or prediabetes, by around 11 mmHg, alongside a one-fifth reduction in blood pressure medicines.⁶ The 28 Day Plan is built around this approach. NICE also advises keeping salt intake low,¹ which matters most for people who are sensitive to it. Cutting ultra-processed food typically reduces dietary salt in any case. Potassium-based salt substitutes are not suitable for older people, pregnant women, people with diabetes or kidney disease, or those on ACE inhibitors or ARBs.¹

Movement

Regular activity lowers blood pressure in its own right. Across 93 trials, endurance exercise lowered blood pressure by 3.5/2.5 mmHg overall and by 8.3/5.2 mmHg in people who already had hypertension; strength training lowered it too, and a small number of studies of isometric exercise (such as wall sits and handgrip holds) showed the largest falls.⁹ Aim for at least 150 minutes a week of moderate activity,² plus strength work twice a week. Blood pressure rises during exercise and falls afterwards, which is normal; people with very high readings should bring them down before hard exertion.

Alcohol, caffeine, smoking and sleep

Alcohol raises blood pressure, and cutting down lowers it; NICE advises a reduced intake for anyone drinking excessively, and the NHS advises keeping to 14 units a week.^1,2 Excess caffeine is discouraged.¹ Smoking does not raise resting blood pressure much, but it multiplies the damage high blood pressure does to arteries, and NICE advises help to stop for every smoker.¹ Poor sleep and untreated sleep apnoea can increase blood pressure; treating apnoea often lowers it.

Home monitoring

A validated upper-arm monitor at home is the best way to see what your own changes are doing. NICE recommends home monitoring for people who want to track their own blood pressure, using the same routine as for diagnosis.¹ Take readings seated, rested, arm supported at heart level, and record the average rather than reacting to single numbers.

Other non-pharmaceutical options

Relaxation techniques are pleasant and may help stress, but NICE no longer recommends them as a treatment for high blood pressure.¹

Medical and pharmaceutical treatments

Blood pressure medicines are effective, well tested and usually taken once a day.^1,2 NICE sets out a stepped approach:¹

• Step 1. The first medicine depends on age, family origin and whether you have type 2 diabetes:
  • an ACE inhibitor (such as ramipril or lisinopril) or an ARB (such as losartan or candesartan), which relax blood vessels by blocking the angiotensin system, for anyone with type 2 diabetes, and for people under 55 who are not of Black African or Caribbean family origin;
  • a calcium-channel blocker (such as amlodipine), which relaxes the artery walls, for people without type 2 diabetes who are 55 or over, or who are of Black African or Caribbean family origin;
  • a thiazide-like diuretic (such as indapamide), which helps the kidneys shed salt and water, if a calcium-channel blocker is not tolerated.

  For people of Black African or Caribbean family origin, NICE prefers an ARB to an ACE inhibitor.

• Step 2. Add a second medicine from the other groups: a calcium-channel blocker or thiazide-like diuretic to an ACE inhibitor or ARB, or an ACE inhibitor, ARB or diuretic to a calcium-channel blocker.
• Step 3. All three together.
• Step 4. If blood pressure is still high on three medicines at the highest doses they can tolerate, this is called resistant hypertension. Readings are confirmed with home or ambulatory monitoring and adherence is checked before a fourth medicine is added or specialist advice sought. The fourth is usually low-dose spironolactone (a diuretic that also blocks aldosterone) if blood potassium allows, or otherwise an alpha-blocker (such as doxazosin) or a beta-blocker (such as bisoprolol).

Before each step up, NICE asks clinicians to check that the current medicines are being taken and at the right doses.¹ Blood tests for kidney function and potassium are needed when starting an ACE inhibitor, ARB or diuretic. ACE inhibitors and ARBs should not be used in pregnancy, when planning a pregnancy or when breastfeeding, except where absolutely necessary.¹

As blood pressure falls with lifestyle change, medicines can usually be stepped down one at a time, normally removing the most recently added medicine first, with home readings to confirm. In the UK general practice study above, blood pressure medicines were reduced by a fifth as people’s metabolic health improved.⁶ Do this with your clinician, not alone: stopping some medicines suddenly can cause a rebound.

Everyone with hypertension should have an annual review of blood pressure, lifestyle, symptoms and medicines.¹

Complications and outlook

Untreated high blood pressure strains the heart and arteries and over years raises the risk of heart attack, stroke, heart failure, kidney disease, eye damage and vascular dementia.² The risk rises steadily with the pressure and with how long it has been high, and it multiplies with the other features of poor metabolic health: high blood sugar, abnormal blood fats and smoking.

The outlook with treatment is good. Lowering blood pressure, by whatever route, reduces the risk of all of these complications.² For most people with essential hypertension, improving metabolic health improves blood pressure and the other risk factors at the same time, which no single tablet does. Many people can then manage on fewer medicines.

When to see a doctor

• Get your blood pressure checked if you are aged 40 or over and have not had it measured in five years, or at any age if a close relative has high blood pressure or you have a large waist, prediabetes, type 2 diabetes, fatty liver or kidney disease.^1,2
• Seek urgent advice (NHS 111) for frequent headaches or blurred vision, or chest pain that comes and goes.²
• A home reading of 180/120 or higher, repeated after five minutes of rest, needs urgent advice the same day from your GP or NHS 111.
• See your GP or practice nurse before changing or stopping any blood pressure medicine, including when your readings have improved.

Summary