What is hypertension?
Hypertension means the force of blood against the artery walls is persistently too high. Blood pressure is recorded as two numbers: systolic (pressure when the heart beats) over diastolic (pressure between beats), measured in mmHg. It is called the 'silent killer' because it causes no symptoms for years while silently damaging the heart, kidneys, brain and eyes.
Blood pressure classification
| Category | Systolic (mmHg) | Diastolic (mmHg) | Action |
|---|---|---|---|
| Normal | <120 | <80 | Maintain healthy lifestyle |
| Elevated | 120–129 | <80 | Lifestyle changes |
| Stage 1 Hypertension | 130–139 | 80–89 | Lifestyle + consider medication |
| Stage 2 Hypertension | ≥140 | ≥90 | Medication + lifestyle |
| Hypertensive Crisis | >180 | >120 | Emergency care immediately |
Blood tests ordered for hypertension
| Test | Why ordered |
|---|---|
| Creatinine / eGFR | Kidney damage from hypertension |
| Urine ACR (albumin:creatinine ratio) | Earliest sign of hypertensive kidney damage |
| Electrolytes (Na, K) | Baseline before starting diuretics or ACE inhibitors |
| Fasting glucose / HbA1c | Diabetes doubles cardiovascular risk |
| Fasting lipid profile | High cholesterol compounds arterial damage |
| TSH | Thyroid disease can cause or worsen hypertension |
| Aldosterone:renin ratio | If hypokalaemia present — screen for primary hyperaldosteronism |
Causes of hypertension
Primary (essential) hypertension — 90% of cases
No single identifiable cause. Risk factors: family history, older age, obesity, high sodium diet, physical inactivity, excess alcohol, smoking, stress and sleep apnoea. It develops gradually over many years.
Secondary hypertension — 10% of cases
A specific underlying cause: chronic kidney disease (most common secondary cause), primary hyperaldosteronism (Conn syndrome — adrenal gland makes too much aldosterone), renal artery stenosis, obstructive sleep apnoea, thyroid disease, pheochromocytoma (adrenal tumour), and medications (NSAIDs, oral contraceptives, decongestants, stimulants).
Organ damage caused by uncontrolled hypertension
- Heart: left ventricular hypertrophy, heart failure, coronary artery disease, heart attack
- Brain: stroke, transient ischaemic attack (TIA), cognitive decline, vascular dementia
- Kidneys: hypertensive nephropathy, chronic kidney disease, kidney failure
- Eyes: hypertensive retinopathy — vessel changes visible on fundoscopy
- Blood vessels: aortic aneurysm, peripheral artery disease
Blood pressure targets
| Patient group | Target BP (mmHg) |
|---|---|
| General adult | <130/80 |
| Age >65 | <130/80 (individualised) |
| Diabetes | <130/80 |
| Chronic kidney disease | <130/80 |
| Hypertensive crisis treatment target | <160/100 initially (not too fast) |
Questions to ask your doctor
- What is causing my high blood pressure?
- Should I have a urine albumin test to check my kidneys?
- Do I need to check for secondary causes?
- What are my cholesterol and blood sugar levels?
- What lifestyle changes will have the biggest impact?