Get emergency help now if a reading is about 180/120 mmHg or higher and comes with chest pain, breathlessness, a severe headache, confusion, weakness or trouble speaking, vision changes or reduced urine. These can mean organ damage (a hypertensive emergency). Call your local emergency number.
Key points
- High blood pressure usually causes no symptoms. Measuring it is the only way to know you have it. WHO estimates that about 44% of adults with hypertension do not know they have it.
- Guidelines differ on where "high" starts: the 2025 AHA/ACC guideline uses 130/80 mmHg, while NICE, ESC and WHO diagnose hypertension at 140/90 mmHg in the clinic.
- Home readings confirm the diagnosis and guide treatment. A home average of 135/85 mmHg corresponds to a clinic reading of 140/90 mmHg.
- First-line medicines are an ACE inhibitor or an ARB, a thiazide or thiazide-like diuretic, and a long-acting dihydropyridine calcium channel blocker. Never combine an ACE inhibitor with an ARB.
- Lifestyle change lowers blood pressure in everyone and is recommended whether or not medicines are needed.
Why it matters
WHO estimates that about 1.4 billion adults aged 30 to 79 have hypertension, and only 23% have it under control. Raised blood pressure damages arteries over years. The 2025 AHA/ACC guideline describes it as the most common modifiable risk factor for coronary artery disease, heart failure, atrial fibrillation, stroke, dementia and chronic kidney disease.
What the numbers mean
Each guideline uses clinic (office) readings for its main categories:
- 2025 AHA/ACC (United States): normal below 120/80; elevated 120 to 129 systolic with diastolic below 80; stage 1 hypertension 130 to 139 systolic or 80 to 89 diastolic; stage 2 hypertension 140/90 or higher. Severe hypertension is above 180/120.
- ESC 2024 (Europe): hypertension is 140/90 or higher. A new "elevated blood pressure" category covers 120 to 139 systolic or 70 to 89 diastolic.
- NICE NG136 (UK): stage 1 is clinic 140/90 to 159/99 with a home or daytime ambulatory average of 135/85 to 149/94. Stage 2 is clinic 160/100 or higher (home average 150/95 or higher). Stage 3 (severe) is clinic 180 systolic or 120 diastolic or higher.
- WHO: hypertension is 140/90 or higher on two different days.
Out-of-office readings run lower than clinic readings. The AHA/ACC table gives these home equivalents: clinic 130/80 matches home 130/80, clinic 140/90 matches home 135/85, and clinic 160/100 matches home 145/90. Comparing the two finds white-coat hypertension (high only in the clinic) and masked hypertension (high only at home).
How to take an accurate home reading
- Use a validated upper-arm monitor with the right cuff size for your arm. Validated device lists exist (for example validatebp.org in the US and the British and Irish Hypertension Society list in the UK). AHA/ACC advises against relying on cuffless devices, including smartwatches, until they prove accurate.
- For 30 minutes before: do not eat, drink caffeine or alcohol, smoke or exercise. Empty your bladder.
- Sit quietly for 5 minutes in a chair with your back supported, feet flat on the floor and legs uncrossed.
- Put the cuff on your bare upper arm, with the arm resting on a table at chest or heart height. Do not talk during the reading.
- Take 2 readings at least 1 minute apart and record both.
- To confirm a diagnosis (NICE): measure twice a day, morning and evening, for at least 4 days and ideally 7. Discard the first day and average the rest.
- Irregular pulse: automated devices may be inaccurate in atrial fibrillation.
When medicines are started
2025 AHA/ACC: medicines plus lifestyle change for everyone with an average of 140/90 or higher. At 130/80 or higher, start medicines in people with cardiovascular disease, previous stroke, diabetes, chronic kidney disease or a 10-year PREVENT risk of 7.5% or more. For lower-risk people at 130/80 or higher, start medicines if blood pressure is still 130/80 or more after 3 to 6 months of lifestyle change. The treatment goal is below 130/80 for most adults.
NICE: discuss medicines for people under 80 with stage 1 hypertension and target organ damage, cardiovascular or kidney disease, diabetes, or a 10-year risk of 10% or more. Offer medicines in stage 2. The clinic target is below 140/90 under age 80 (home below 135/85) and below 150/90 at 80 and over (home below 145/85).
ESC 2024: the systolic target for treated adults is 120 to 129 mmHg if tolerated, or as low as reasonably achievable in people who are frail, very old or have symptoms on standing. WHO: the goal is below 140/90 for most people and below 130/80 for people with cardiovascular disease, diabetes, chronic kidney disease or high cardiovascular risk.
First-line medicines
- ACE inhibitors (such as lisinopril, enalapril, ramipril) or ARBs (such as losartan, telmisartan). If an ACE inhibitor causes cough, NICE advises switching to an ARB.
- Thiazide or thiazide-like diuretics (such as chlorthalidone, indapamide, hydrochlorothiazide). NICE prefers thiazide-like diuretics such as indapamide when starting or changing treatment.
- Long-acting dihydropyridine calcium channel blockers (such as amlodipine). Ankle swelling is a common reason to switch.
The choice also depends on other conditions such as heart failure, diabetes or kidney disease. NICE suggests a calcium channel blocker first for people aged 55 and over, and for people of Black African or African-Caribbean family origin without diabetes. It suggests an ACE inhibitor or ARB for people under 55 who are not of Black African or African-Caribbean family origin, and for anyone with type 2 diabetes. For people of Black African or African-Caribbean family origin, NICE suggests an ARB in preference to an ACE inhibitor.
If one drug is not enough, a second first-line class is added, then all three (ACE inhibitor or ARB, calcium channel blocker and thiazide-like diuretic). For stage 2 hypertension, AHA/ACC prefers starting with 2 first-line drugs in a single combination pill. Resistant hypertension may need spironolactone as a fourth drug.
Beta-blockers are not routine first-line drugs. AHA/ACC found them less effective at preventing stroke, with more side effects. They are kept for people with a compelling reason, such as heart failure with reduced ejection fraction or coronary heart disease.
Safety: what to check on treatment
- Never combine an ACE inhibitor with an ARB, or either with aliskiren. The combination raises the risk of kidney injury and high potassium without benefit.
- Blood tests (kidney function and electrolytes) 2 to 4 weeks after starting or increasing an ACE inhibitor, ARB, diuretic or mineralocorticoid antagonist. A rise in creatinine (eGFR drop up to 30%) can be expected with ACE inhibitors and ARBs. A larger, persistent fall needs review.
- Pregnancy: ACE inhibitors, ARBs and aliskiren harm the fetus in the second and third trimesters. Anyone who could become pregnant should plan with the prescriber. Labetalol has the most reassuring safety data in pregnancy.
- Other medicines that raise blood pressure or blunt treatment: NSAIDs (such as ibuprofen), decongestants (such as pseudoephedrine), stimulants, and high caffeine intake.
- Older adults: check for dizziness or falls on standing. NICE defines postural hypotension as a systolic drop of 20 mmHg or a diastolic drop of 10 mmHg after at least 1 minute of standing.
- Salt substitutes containing potassium chloride: NICE advises against them for older people and people with diabetes, kidney disease or pregnancy, and in people taking ACE inhibitors or ARBs. AHA/ACC is more positive: it says they can help lower blood pressure, but advises extra monitoring in kidney disease or with medicines that raise potassium. Ask your doctor or pharmacist before using one.
Lifestyle changes, with numbers
- Sodium: no more than 2,300 mg a day, ideally 1,500 mg for most adults (AHA/ACC).
- Potassium from food: 3,500 to 5,000 mg a day, unless kidney disease or medicines make this unsafe. NICE does not recommend potassium, calcium or magnesium supplements to lower blood pressure.
- Diet: the DASH eating plan ranked as the most effective lifestyle measure.
- Weight: systolic blood pressure falls by about 1 mmHg for every 1 kg lost.
- Activity: at least 150 minutes of moderate activity a week plus resistance exercise on at least 2 days.
- Alcohol: less is better, and none is best. If you drink, the AHA/ACC limit is 1 drink a day for women and 2 for men.
- Caffeine below 300 mg a day. Stop smoking.
Red flags: when to get urgent help
- A reading of about 180/120 or higher with chest pain, breathlessness or signs of heart failure, new confusion, severe headache, weakness, trouble speaking, vision changes or much less urine. AHA/ACC lists heart failure with fluid on the lungs, stroke, bleeding in the brain, encephalopathy, acute kidney injury and aortic dissection as forms of hypertensive emergency.
- Bleeding at the back of the eye or swelling of the optic disc (accelerated hypertension). NICE advises same-day specialist assessment.
- Episodes of headache, palpitations, pallor and sweating with swinging blood pressure (possible phaeochromocytoma, also same-day referral in NICE).
- High blood pressure in pregnancy or in the weeks after birth. Pre-eclampsia can develop before, during or after delivery and needs prompt assessment. Fits (eclampsia) are an emergency.
A very high reading without symptoms or organ damage (severe hypertension, once called hypertensive urgency) is usually not an emergency. Repeat the reading after resting, then contact your doctor promptly. AHA/ACC advises restarting or increasing oral medicines as an outpatient rather than lowering blood pressure rapidly.
Frequently asked questions
Can I tell when my blood pressure is high?
Usually not. Most people have no symptoms. Headache, dizziness or nosebleeds tend to appear only at very high levels, if at all. Regular measurement is the only way to know.
Why are my home readings lower than in the clinic?
Readings often rise in a clinic, so guidelines use lower home thresholds (135/85 rather than 140/90). If home readings are much higher than in the clinic, tell your doctor: this is masked hypertension.
Can I stop my medicine once my blood pressure is normal?
Not on your own. Normal readings on treatment usually mean the medicine is working. Any change to the dose should be planned with the prescriber, with follow-up readings.
Sources
- Jones DW et al. 2025 AHA/ACC guideline for the prevention, detection, evaluation and management of high blood pressure in adults. Hypertension, 2025. ahajournals.org
- NICE. Hypertension in adults: diagnosis and management (NG136), 2019, last updated 2026. nice.org.uk/guidance/ng136
- American College of Cardiology. 2024 ESC guidelines for the management of elevated blood pressure and hypertension: key points. acc.org
- World Health Organization. Hypertension, fact sheet, 2025. who.int
- US Centers for Disease Control and Prevention. Measure your blood pressure. cdc.gov
This article is for education and does not replace advice from a doctor, nurse or pharmacist who knows the person's history and medicines.
