What Is Hypertension? Blood Pressure, Causes, and Treatment

Understanding Blood Pressure Readings

Blood pressure is recorded as two numbers: systolic pressure over diastolic pressure, expressed in millimeters of mercury (mmHg). The systolic value measures the pressure in the arteries when the heart beats, while the diastolic value measures the pressure between beats when the heart rests. A normal reading is defined as below 120/80 mmHg by most international guidelines.

Hypertension is classified in stages. Stage 1 hypertension ranges from 130–139 systolic or 80–89 diastolic. Stage 2 hypertension is 140/90 mmHg or higher. A hypertensive crisis—requiring immediate medical attention—occurs above 180/120 mmHg. Elevated blood pressure (formerly called prehypertension) sits between 120–129 systolic with a diastolic below 80.

Primary vs. Secondary Hypertension

Approximately 90–95% of hypertension cases are classified as primary (or essential) hypertension, meaning no single identifiable cause is found. Instead, it develops gradually over years through the interaction of genetic predisposition and lifestyle factors. Secondary hypertension, accounting for the remaining 5–10%, results from an identifiable underlying condition.

Common causes of secondary hypertension include chronic kidney disease, renal artery stenosis, primary aldosteronism, obstructive sleep apnea, thyroid disorders, and the use of certain medications such as oral contraceptives, NSAIDs, and decongestants. Identifying and treating the underlying cause of secondary hypertension can often restore normal blood pressure without lifelong medication.

Risk Factors and the Silent Killer

Hypertension is frequently called the silent killer because it produces no symptoms in the vast majority of cases, even when blood pressure is dangerously elevated. Most people with hypertension feel entirely normal, which is why routine screening is essential. The condition is typically discovered incidentally during a routine medical check-up or when a complication such as a heart attack or stroke occurs.

Major modifiable risk factors include a sedentary lifestyle, a diet high in sodium and low in potassium, obesity, excessive alcohol consumption, and smoking. Non-modifiable risk factors include older age, male sex (though risk equalizes after menopause in women), family history, and ethnicity—Black adults are disproportionately affected, with earlier onset and higher severity. Chronic psychological stress also contributes to sustained blood pressure elevation.

Cardiovascular and Organ Complications

Sustained elevated blood pressure forces the heart to work harder, leading to left ventricular hypertrophy—a thickening of the heart muscle that impairs its ability to pump efficiently and predisposes to heart failure. The increased mechanical stress damages arterial walls, accelerating atherosclerosis (plaque buildup), which dramatically raises the risk of myocardial infarction and ischemic stroke.

Beyond the heart and brain, hypertension damages the kidneys by narrowing the small arteries that supply the glomeruli, eventually causing hypertensive nephropathy and chronic kidney disease. It also damages the retinal blood vessels, a condition called hypertensive retinopathy, which can impair vision. Aortic aneurysm and peripheral artery disease are additional serious complications of long-standing uncontrolled hypertension.

Lifestyle Interventions

Lifestyle modification is first-line therapy for Stage 1 hypertension and an essential adjunct to medication at all stages. The DASH (Dietary Approaches to Stop Hypertension) diet—rich in fruits, vegetables, whole grains, and low-fat dairy while limiting sodium—can reduce systolic blood pressure by 8–14 mmHg. Sodium restriction to below 2,300 mg per day (ideally 1,500 mg) is particularly effective.

Regular aerobic exercise of at least 150 minutes per week at moderate intensity can lower systolic pressure by 5–8 mmHg. Weight loss of 10 kg in overweight individuals reduces systolic pressure by approximately 6 mmHg. Limiting alcohol to no more than one drink per day for women and two for men, and eliminating tobacco use, provide additional reductions. Stress management through mindfulness or cognitive-behavioral techniques offers modest but meaningful benefits.

Pharmacological Treatment

When lifestyle changes are insufficient, antihypertensive medications are prescribed. First-line agents recommended by most guidelines include thiazide diuretics (e.g., hydrochlorothiazide), ACE inhibitors (e.g., lisinopril), angiotensin II receptor blockers (ARBs) (e.g., losartan), and calcium channel blockers (e.g., amlodipine). The choice depends on individual comorbidities, ethnicity, and tolerability.

Many patients require two or more medications to achieve their target blood pressure. Combination pills improve adherence by reducing pill burden. Beta-blockers, aldosterone antagonists, and centrally acting agents are used in specific situations. Importantly, antihypertensive treatment must be continued long-term; stopping medication abruptly can cause rebound hypertension. Regular home blood pressure monitoring empowers patients to track their response to treatment and detect white-coat or masked hypertension.