High blood pressure (hypertension) - what the numbers mean

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Blood pressure is the force your heart uses to push blood around your body. It is measured in millimetres of mercury (mmHg) and written as two numbers - for example, 130/80. The top number (systolic) is the pressure when your heart beats. The bottom number (diastolic) is the pressure when your heart rests between beats.

What the numbers mean

For most adults, a healthy blood pressure is below 130/80 mmHg. High blood pressure (hypertension) is usually diagnosed when readings are consistently at or above 140/90 mmHg, though your doctor may use a lower target if you have diabetes or kidney disease.

High blood pressure rarely causes symptoms. Most people feel completely normal even when their readings are high - which is why it is sometimes called the "silent" condition. The damage it causes happens slowly, over years, to your heart, arteries, kidneys, and eyes.

Why it matters

Untreated high blood pressure is one of the leading causes of heart attack, stroke, kidney disease, and heart failure in New Zealand. The good news is that controlling it - even partially - significantly reduces that risk. Most people with well-controlled blood pressure live full and active lives.

Things you can do yourself

Lifestyle changes can lower blood pressure meaningfully, sometimes enough to delay or reduce the need for medicines:

• Reduce salt. Aim for less than 5 g of sodium per day. Most salt in the NZ diet comes from processed foods, bread, sauces, and takeaways - not the saltshaker. Reading food labels helps.
• Move more. Aim for at least 30 minutes of moderate activity (brisk walking, swimming, cycling) on most days of the week.
• Drink less alcohol. Stick to the NZ guidelines - no more than 10 standard drinks per week, with at least two alcohol-free days.
• Maintain a healthy weight. Even losing 5 kg can reduce blood pressure noticeably if you are overweight.
• Stop smoking. Smoking does not directly cause chronic high blood pressure but massively increases your cardiovascular risk. Free support is available via Quitline (0800 778 778).
• Manage stress. Chronic stress can raise blood pressure. Exercise, adequate sleep, and talking to someone can all help.

Medicines

If lifestyle changes are not enough, or if your blood pressure is very high, your doctor will recommend medicine. There are several types - ACE inhibitors, ARBs, calcium channel blockers, and thiazide diuretics are the most common. Many people end up on more than one. It often takes a few adjustments to find what works best for you.

Blood pressure medicines usually need to be taken every day for life. Do not stop them without talking to your doctor, even if you feel well. Feeling well is often a sign the medicine is working.

Monitoring at home

Home blood pressure monitors are widely available from pharmacies in NZ. Regular home readings can give your doctor a more accurate picture than a single clinic reading. Sit quietly for five minutes before measuring, take two readings two minutes apart, and note the results. Bring the log to your appointments.

When to get help quickly

Go to the emergency department or call 111 if you have a very high reading (above 180/120) along with any of these:

• Chest pain or tightness
• Sudden severe headache
• Blurred or double vision
• Difficulty speaking or weakness in one arm or leg
• Shortness of breath

A high number alone without symptoms is worth calling your GP about, but is usually not an emergency.

Questions to ask your doctor

• What is my blood pressure target?
• When should I come back for a recheck?
• Should I be checking my blood pressure at home?
• Are there any medicines I should avoid (including over-the-counter medicines like ibuprofen)?