Reading the numbers

The top number, systolic, is the pressure while the heart contracts. The bottom, diastolic, is the pressure between beats. Both matter; systolic becomes the more important predictor with age as arteries stiffen.

The 2017 American College of Cardiology and American Heart Association guideline sets these categories:

  • Normal — under 120 and under 80 mmHg
  • Elevated — 120 to 129 systolic and under 80 diastolic
  • Stage 1 hypertension — 130 to 139 systolic or 80 to 89 diastolic
  • Stage 2 hypertension — 140 or higher systolic, or 90 or higher diastolic
  • Hypertensive crisis — above 180 or above 120; seek immediate care, especially with chest pain, breathlessness, weakness, or vision change

A diagnosis is based on multiple readings over time, often including home or ambulatory monitoring, not a single office measurement.

Measuring accurately at home

Most home measurement errors push readings upward, and the size of the error is not trivial — poor technique can add 10 to 20 mmHg. Getting it right matters as much as the device.

  • Use a validated upper-arm cuff, correctly sized. Wrist and finger devices are less reliable.
  • Avoid caffeine, exercise, and smoking for 30 minutes beforehand, and empty your bladder.
  • Sit quietly for five minutes with back supported and feet flat on the floor.
  • Rest the arm on a surface at heart level, with the cuff on bare skin.
  • Do not talk during the measurement.
  • Take two or three readings a minute apart and record the average.

Measure at consistent times, typically morning and evening, and bring a week of readings to appointments. Take the monitor with you once so it can be checked against the clinic device.

Sodium, potassium, and the DASH pattern

DASH — Dietary Approaches to Stop Hypertension — was designed and tested specifically to lower blood pressure, and it does so within a few weeks. It emphasises vegetables, fruit, whole grains, low-fat dairy, legumes, nuts, and lean protein, with limited saturated fat, added sugar, and sodium.

General guidance is to keep sodium below 2,300 mg a day, with roughly 1,500 mg ideal for many adults with high blood pressure. Combining DASH with sodium reduction produces a larger fall than either alone. Most dietary sodium comes from packaged and restaurant food, not the salt shaker.

Potassium works in the opposite direction, and diets rich in fruit, vegetables, legumes, and dairy tend to be higher in it. Potassium supplements and potassium-based salt substitutes are not appropriate for everyone — particularly with kidney disease or certain medications — so check first.

Activity, weight, alcohol, and stress

Several non-drug changes have well-quantified effects, and they add up.

  • Physical activity — regular aerobic activity typically lowers systolic pressure by roughly 5 to 8 mmHg. Dynamic resistance training adds a further effect.
  • Weight loss — approximately 1 mmHg per kilogram lost for many people with excess weight.
  • Alcohol reduction — meaningful falls in regular drinkers who cut back.
  • Sodium reduction — commonly 5 to 6 mmHg systolic, larger in salt-sensitive individuals.
  • Sleep — treating obstructive sleep apnea improves blood pressure in people who have it.

Stress raises blood pressure acutely; its role in sustained hypertension is less certain, but it drives habits that clearly matter. Nicotine raises pressure sharply with every use.

Medication and monitoring over time

When lifestyle measures are not sufficient, or when risk is high from the start, medication is added. Several classes are used — including ACE inhibitors, angiotensin receptor blockers, calcium channel blockers, and thiazide diuretics — and many people need more than one to reach target. Choice depends on age, other conditions, kidney function, pregnancy status, and side effects; dosing is individualised by the prescriber.

Because high blood pressure is symptomless, people often stop medication when they feel fine. That is one of the most common reasons control is lost. If side effects are the issue, alternatives usually exist.

  • Keep a home log and bring it to every appointment.
  • Ask what your target is — it differs by age and other conditions.
  • Report side effects rather than stopping quietly.
  • Seek emergency care for 180/120 or above with chest pain, breathlessness, weakness, difficulty speaking, or vision change.