What is hypertension?
Blood pressure is the force exerted by circulating blood against the walls of your arteries. Every heartbeat creates a wave of pressure — highest during the contraction phase (systole) and lowest during the relaxation phase (diastole). This is why blood pressure is expressed as two numbers: systolic over diastolic, measured in millimetres of mercury (mmHg).
Hypertension occurs when this force is persistently elevated above normal levels. The current threshold, established by the 2017 ACC/AHA guidelines, is 130/80 mmHg or above. At this level, arterial walls experience chronic mechanical stress that, over years and decades, causes structural damage — stiffening, microtears that become sites of plaque deposition, and eventually aneurysms.
What makes hypertension particularly dangerous is its silence. Most people feel completely normal with significantly elevated blood pressure. Organ damage accumulates invisibly for years until a catastrophic event — heart attack, stroke, kidney failure — finally reveals what has been happening internally.
Blood pressure categories
| Category | Systolic | Diastolic | Action | |
|---|---|---|---|---|
| Normal | <120 mmHg | and | <80 mmHg | Maintain healthy habits |
| Elevated | 120–129 | and | <80 | Lifestyle changes; recheck in 3–6 months |
| Stage 1 Hypertension | 130–139 | or | 80–89 | Lifestyle ± medication depending on CV risk |
| Stage 2 Hypertension | ≥140 | or | ≥90 | Lifestyle + medication recommended |
| Hypertensive Crisis | ≥180 | and/or | ≥120 | Seek emergency care immediately |
Primary vs. secondary hypertension
Primary (essential) hypertension — 90–95% of cases
The vast majority of hypertension has no single identifiable cause. It develops gradually from the interaction of genetic predisposition with environmental factors including excess dietary sodium, physical inactivity, obesity, alcohol, chronic stress, and ageing. There is no cure, but it is highly manageable.
Secondary hypertension — 5–10% of cases
When hypertension has an identifiable underlying cause, it is called secondary. Treating the underlying condition may normalise or significantly improve blood pressure. Secondary causes should be investigated in: younger patients (<30) with no obvious risk factors, patients with resistant hypertension, sudden onset of significant hypertension, or specific clinical clues.
| Secondary cause | Prevalence | Clinical clues | Diagnosis |
|---|---|---|---|
| Obstructive sleep apnoea (OSA) | ~30% of resistant HTN | Snoring, daytime sleepiness, obesity, morning headaches | Overnight sleep study or home sleep test |
| Primary aldosteronism | ~5–10% of hypertensives | Resistant HTN, low potassium, adrenal incidentaloma | Aldosterone-to-renin ratio; adrenal CT; adrenal vein sampling |
| Renovascular disease | ~1–5% | Resistant HTN in young woman; renal artery bruit; flash pulmonary oedema | CT or MR angiography; Duplex ultrasound |
| Chronic kidney disease | Very common in CKD | Elevated creatinine, proteinuria | eGFR; urine albumin-to-creatinine ratio |
| Thyroid disease | Hypo: diastolic HTN; Hyper: systolic HTN | Weight change, fatigue, palpitations | TSH, free T4 |
| Phaeochromocytoma | Rare (<0.5%) | Episodic HTN, headache, sweating, palpitations | Plasma/urine metanephrines; adrenal imaging |
| Medications/substances | Common | NSAIDs, oral contraceptives, decongestants, stimulants, liquorice, cocaine | Medication review and discontinuation trial |
Symptoms and warning signs
This is the most important thing to understand about hypertension: it almost never causes symptoms until it reaches crisis levels or has already caused organ damage. Blood pressure must be measured — it cannot be felt.
Severe headache · Chest pain · Shortness of breath · Blurred or double vision · Nausea/vomiting · Confusion or altered consciousness · Nosebleed that won't stop · Weakness or numbness on one side · Difficulty speaking
Causes and risk factors
Non-modifiable factors
- Age: Blood pressure rises with age as arteries stiffen. More than 70% of adults over 65 have hypertension.
- Genetics / family history: Hypertension is 30–60% heritable. A first-degree relative with hypertension roughly doubles your risk.
- Race/ethnicity: African Americans develop hypertension earlier, more severely, and with higher rates of end-organ damage.
- Sex: Before age 55, men have higher rates; after menopause, women's rates equalise and eventually exceed men's.
Modifiable factors
🧂 Excess Sodium
- Average intake: 3,400 mg/day
- Target: <2,300 mg/day
- Ideal for HTN: <1,500 mg/day
- Reducing 1,000 mg lowers BP ~5 mmHg
⚖️ Obesity
- Every 10 kg weight gain raises BP ~3 mmHg
- Abdominal fat especially harmful
- 5–10% weight loss produces meaningful BP reduction
- Linked to sleep apnoea (secondary HTN)
🛋️ Physical Inactivity
- Regular aerobic exercise lowers BP 5–8 mmHg
- 150 min/week is target
- Even 30-min sessions have acute effect
- Isometric exercises show emerging benefit
🍺 Alcohol
- Heavy drinking raises BP significantly
- More than 2 drinks/day increases risk in men
- Alcohol interferes with medications
- Reducing alcohol lowers BP 3–4 mmHg
Diagnosis and measurement
How to measure blood pressure correctly
- Sit quietly for 5 minutes before measuring — do not measure immediately after arriving
- Sit with back supported, feet flat on floor, arm at heart level — no crossing legs
- Use a validated upper-arm cuff — wrist monitors are less accurate
- No caffeine, exercise, or smoking for 30 minutes before measurement
- Take 2–3 readings 1 minute apart; use the average
- Check both arms at first — use the arm with the higher reading going forward
- Record time, date, and reading — bring the log to appointments
Home BP monitoring (HBPM): The AHA recommends home monitoring for all hypertensive patients. A week of twice-daily home readings provides far more diagnostic information than a single office visit. It also detects white-coat hypertension (normal at home, elevated in clinic) and masked hypertension (normal in clinic, elevated at home).
Ambulatory BP monitoring (ABPM): A cuff worn for 24 hours taking readings every 15–30 minutes. The gold standard for diagnosing hypertension. Reveals daytime vs nighttime patterns — non-dipping (BP fails to fall at night) is an independent cardiovascular risk factor.
Medications for hypertension
| Drug class | Examples | BP reduction | Best for | Key side effects |
|---|---|---|---|---|
| ACE inhibitors | Lisinopril, Ramipril, Perindopril | 10–15/6–8 mmHg | Diabetes, CKD with proteinuria, post-MI, heart failure | Dry cough (10–15%); avoid in pregnancy; rarely angioedema |
| ARBs (Sartans) | Losartan, Valsartan, Olmesartan | 10–15/6–8 mmHg | ACE inhibitor intolerance; similar indications to ACEi | No cough; angioedema rare; avoid in pregnancy |
| Calcium channel blockers | Amlodipine, Lercanidipine (DHP); Diltiazem, Verapamil (non-DHP) | 10–15/6–8 mmHg | Isolated systolic HTN; elderly; angina; Black patients | Ankle oedema (DHPs); bradycardia/constipation (non-DHPs) |
| Thiazide/thiazide-like diuretics | Chlorthalidone (preferred), Indapamide, Hydrochlorothiazide | 8–12/4–6 mmHg | Volume-dependent HTN; elderly; Black patients; combination therapy | Low potassium; low sodium; elevated uric acid; ED |
Combination therapy: Most Stage 2 patients require two or more medications. Starting with a single-pill combination (SPC) improves adherence significantly. A common first-line combination: ACE inhibitor/ARB + CCB or thiazide diuretic.
| Drug class | Examples | Use case | Notes |
|---|---|---|---|
| Beta-blockers | Bisoprolol, Metoprolol, Carvedilol | Heart failure, post-MI, arrhythmia, angina — not first-line for uncomplicated HTN | Avoid in asthma/COPD; can mask hypoglycaemia; erectile dysfunction |
| Potassium-sparing diuretics | Spironolactone, Eplerenone | Resistant HTN; heart failure; primary aldosteronism | Spironolactone causes gynaecomastia; monitor potassium with ACEi/ARB |
| Alpha-blockers | Doxazosin, Prazosin | Resistant HTN; benign prostatic hyperplasia | Orthostatic hypotension — titrate carefully; not first-line |
| Centrally acting agents | Clonidine, Methyldopa | Resistant HTN; methyldopa preferred in pregnancy | Rebound hypertension on abrupt discontinuation of clonidine |
Resistant hypertension is defined as blood pressure above target despite optimal doses of three antihypertensive medications from different classes — including a diuretic. True resistant HTN occurs in about 10–15% of treated hypertensives.
Before labelling "resistant," exclude: poor medication adherence (the most common cause), white-coat effect (confirm with ABPM), secondary causes (especially OSA and primary aldosteronism), interfering medications (NSAIDs, decongestants, stimulants, oral contraceptives), and inadequate diuretic therapy.
When true resistance is confirmed, the most evidence-based next step is adding spironolactone 25–50 mg/day — the PATHWAY-2 trial showed it was the most effective add-on agent. Novel approaches include:
- Renal denervation: Catheter-based procedure ablating sympathetic nerves around the renal artery. Phase 3 trials show modest BP reductions of 8–10 mmHg systolic. FDA approval pending in the U.S.
- Baroreflex activation therapy (BAT): Implantable device stimulating carotid baroreceptors to lower sympathetic tone. Approved in the U.S. for resistant hypertension.
Lifestyle changes: the evidence
| Intervention | Expected BP reduction | Evidence quality | Practical target |
|---|---|---|---|
| Sodium reduction | 5–6/2–3 mmHg | High | <2,300 mg/day; avoid processed foods, canned goods, restaurant meals |
| Weight loss | 5/4 mmHg per 5 kg lost | High | Even 5 kg loss produces meaningful effect |
| DASH diet | 11/5 mmHg | High | Fruits, vegetables, low-fat dairy, whole grains; limit saturated fat and sodium |
| Aerobic exercise | 5–8/3–4 mmHg | High | 150+ min/week moderate intensity; swimming and cycling particularly effective |
| Isometric exercise | 8/4 mmHg | Moderate-High | Wall squat 4 × 2-min holds, 3×/week — strong 2023 meta-analysis evidence |
| Alcohol reduction | 3–4/2 mmHg | High | ≤1 drink/day for women, ≤2 for men; ideally minimise |
| Potassium increase | 4–5/2–3 mmHg | Moderate | 3,500–5,000 mg/day from food — check with doctor if on ACEi/ARB |
| Stress reduction (MBSR) | 3–4/2 mmHg | Moderate | Mindfulness-based stress reduction, yoga, device-guided slow breathing |
The DASH diet is the most rigorously studied dietary intervention for hypertension. A full DASH diet combined with sodium restriction (1,500 mg/day) lowers systolic BP by 11 mmHg — equivalent to a single antihypertensive drug. Key principles: 4–5 servings daily of fruits and vegetables each, 2–3 servings low-fat dairy, whole grains as the main carbohydrate source, nuts and legumes 4–5 times per week, limited red meat and sweets.
Complications of uncontrolled hypertension
| Target organ | Complication | Prevention |
|---|---|---|
| Brain | Stroke (ischaemic and haemorrhagic), TIA, vascular dementia, hypertensive encephalopathy | BP control reduces stroke risk 35–40% |
| Heart | Coronary artery disease, heart attack, left ventricular hypertrophy, heart failure (HFpEF) | Every 10 mmHg SBP reduction cuts CV events ~25% |
| Kidneys | Hypertensive nephropathy, chronic kidney disease, end-stage renal disease | ACEi/ARBs specifically protect renal function |
| Eyes | Hypertensive retinopathy, retinal artery/vein occlusion, visual loss | BP control; annual fundoscopy in severe HTN |
| Arteries | Aortic aneurysm, aortic dissection, peripheral artery disease | BP target <130/80; smoking cessation |
Frequently asked questions
A reading of 180/120 mmHg or above constitutes a hypertensive crisis. Without symptoms (no chest pain, headache, vision changes, or neurological symptoms), this is an urgency — contact your doctor immediately for urgent medication adjustment. With any of those symptoms, this is an emergency — call 911 immediately, as acute end-organ damage may be occurring.
Primary hypertension cannot be cured but can be very effectively controlled. Some patients who achieve significant sustained weight loss and lifestyle transformation do reach normal blood pressure without medication — but this requires lifelong commitment. Secondary hypertension may resolve if the underlying cause (e.g., primary aldosteronism treated surgically, sleep apnoea treated with CPAP) is successfully addressed.
This is one of the most persistent myths in medicine. Mild to moderate hypertension — even significantly elevated readings — typically causes no headaches whatsoever. Headaches are a symptom of hypertensive crisis (typically ≥180/120 mmHg). Multiple large studies have found no meaningful correlation between routine hypertension and ordinary headaches. The only reliable approach is to actually measure your blood pressure.
In 90–95% of cases (primary hypertension), there is no single identifiable cause — it results from a combination of genetic predisposition, age-related arterial stiffening, excess sodium intake, physical inactivity, obesity, alcohol, and chronic stress. The remaining 5–10% (secondary hypertension) is caused by identifiable conditions: obstructive sleep apnoea, primary aldosteronism, renovascular disease, chronic kidney disease, thyroid disorders, phaeochromocytoma, and certain medications.
- Whelton PK, et al. 2017 ACC/AHA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults. JACC. 2018;71(19):e127–e248.
- Williams B, et al. 2018 ESC/ESH Guidelines for the management of arterial hypertension. Eur Heart J. 2018;39(33):3021–3104.
- Sacks FM, et al. Effects on Blood Pressure of Reduced Dietary Sodium and the DASH Diet (DASH-Sodium). NEJM. 2001;344(1):3–10.
- Williams B, et al. Spironolactone versus placebo, bisoprolol, and doxazosin to determine the optimal treatment for drug-resistant hypertension (PATHWAY-2). Lancet. 2015;386(10008):2059–2068.
- Mahfoud F, et al. Cardiovascular risk reduction by renal denervation — a meta-analysis. Lancet. 2022;399(10341):2116–2124.
- Dolan E, et al. Superiority of ambulatory over clinic blood pressure measurement in predicting mortality. Hypertension. 2005;46(1):156–161.