Southern Cross Medical Library

Southern Cross Medical Library

High blood pressure is when the pressure of your blood on your artery walls is abnormally high, potentially causing artery damage and health problems over the long term.

Known medically as hypertension, high blood pressure affects up to one in five New Zealanders and is a significant contributor to the incidence of heart disease and stroke. Nearly two-thirds of people admitted to hospital with a heart attack have high blood pressure.

It is advisable, therefore, to have your blood pressure measured regularly, such as during routine visits to your doctor. High blood pressure is preventable and treatable, through lifestyle changes and medications.

General information

Arteries are blood vessels that carry blood from your heart to all parts of your body (veins are the blood vessels that carry your blood back to your heart). As blood travels from your heart it exerts pressure against the artery walls. A blood pressure reading is a measurement of this force and has two components:

  • The higher number is the “systolic” reading and is the pressure in the arteries when the heart beats, forcing blood around the body.
  • The lower number is the “diastolic” reading and is the pressure in the arteries when the heart is relaxed after a beat.

The New Zealand Heart Foundation says an ideal blood pressure for most people is 120/75 mmHg or less, while high blood pressure is when blood pressure is consistently around or above 140/90 mmHg. It is recommended that people with a history of heart disease, diabetes, or a high risk of heart attack or stroke, lower their blood pressure to less than 130/80 mmHg.

Blood pressure varies throughout the day in response to factors such as excitement, stress, and exercise.

Signs and symptoms

There are usually no signs and symptoms of hypertension until the condition has been present for a long time, causing damage to blood vessels and internal organs (particularly the heart and kidneys).

In general, the longer high blood pressure is present and the higher it is, the more likely it is that damage will occur. People with prolonged hypertension are at greater risk of developing medical conditions such as:

  • Stroke
  • Enlarged heart
  • Heart attack
  • Kidney failure
  • Heart failure
  • Aneurysm (a bulge in an artery wall which, if ruptured, can lead to serious internal bleeding)
  • Damage to the retina of the eye.


In approximately 95% of cases there is no one specific cause of hypertension. This is referred to as “essential” or primary hypertension. In the other 5% of cases hypertension is caused by another medical condition such as kidney disease, diabetes, or various adrenal gland disorders. This is called secondary hypertension. With secondary hypertension, treating the underlying cause will often relieve high blood pressure.

Some people have a condition known as "white coat" hypertension. This is where the blood pressure goes up when they get it checked – usually due to anxiety. They may require 24-hour blood pressure monitoring to determine if they really do have hypertension or not.

Risk factors

It can be difficult to predict who will develop hypertension but there are various known risk factors for the condition, the most important of which is being overweight.

Known risk factors include:

  • Being overweight or obese
  • Increasing age
  • Inactive lifestyle
  • Excessive alcohol intake (more than two standard drinks per day)
  • Family history of hypertension
  • Male gender (although female risk increases after menopause)
  • A diet high in salt (sodium)
  • Smoking or vaping (tobacco and vape juice contain nicotine, which temporarily raises blood pressure)
  • Stress
  • Excessive caffeine intake (eg: coffee, tea, and some soft drinks)
  • Use of oral contraceptive medications
  • Adrenal and thyroid gland disorders (the adrenal and thyroid glands produce hormones that help control heart rate and blood pressure)
  • Use of illegal drugs, e.g. cocaine, amphetamines
  • Certain chronic medical conditions, e.g. kidney disease, diabetes, and sleep apnoea.


For a diagnosis of hypertension to be made a person’s blood pressure must be elevated for several readings over time. If blood pressure readings remain elevated your doctor may order blood tests, urine tests, an ECG (electrocardiogram, a test that produces a tracing of the heart's electrical activity), a chest x-ray, echocardiogram (a test that uses sound waves to create detailed images of the beating heart), and examine the blood vessels in the eye with a special light (ophthalmoscope). These tests assess for any damage already caused by the hypertension.


For cases of essential hypertension, treatment is aimed at controlling the hypertension and maintaining blood pressure at an acceptable level. In cases of secondary hypertension, treatment is aimed at identifying and treating the underlying cause as well as controlling the hypertension.

A decision as to whether or not to treat hypertension will depend on a number of factors including the patient’s age, the level of blood pressure, and other medical conditions and risk factors.

In general, treatment of hypertension will focus on two main areas – lifestyle changes and medications. If your blood pressure is not significantly elevated the doctor may initially recommend lifestyle changes to lower the blood pressure. Your blood pressure will be regularly monitored for any improvement. However, if lifestyle changes alone do not adequately lower blood pressure within a 3- to 6-month period, then a combination of lifestyle changes and medications may be recommended.

Lifestyle changes:


There are a wide variety of medications available to treat hypertension, all of which work in different ways. It may take some time to determine the right medication – one that lowers your blood pressure to a better level, but with minimal side effects.

Some of the different classes of medications used to treat hypertension include:

  • Diuretics (e.g. bendrofluazide) work by removing excess water and sodium from the body in the form of urine. This decreases the volume of blood circulating around the body, helping to reduce blood pressure
  • Beta-blockers (e.g. metoprolol) act on the nervous system to slow the heart rate, which puts less pressure on the heart, as well as helping to relax the blood vessels
  • Calcium channel blockers (e.g. diltiazem) work by slowing the entry of calcium into the heart and blood vessel walls. This relaxes the blood vessels so they dilate (widen) and thus lower blood pressure
  • Angiotensin-converting enzyme (ACE) inhibitors (e.g. cilazapril) work by blocking the formation of a particular chemical in the blood called angiotensin. This helps to dilate blood vessel walls and reduce salt and water retention in the body and so decreases blood pressure
  • Angiotensin receptor blockers (ARBs) (e.g. losartan) work by blocking the action of angiotensin in the body, which is a hormone that relaxes blood vessels thus lowering blood pressure
  • Vasodilators (e.g. hydralazine) relax the muscles in the walls of the blood vessels causing them to dilate and so reduce blood pressure.

It is sometimes necessary to take more than one type of medication to effectively treat hypertension. Some of these medications may not be appropriate if other pre-existing medical conditions are present. For this reason, it is important to talk to your doctor about other medical conditions and any other medications being taken.

It is also important to talk to your doctor about any side effects experienced whilst taking blood pressure medications (especially in the first few weeks) as either the dose or the medication may need to be altered. Side effects may include fatigue, cold hands and feet, cough, skin rash, impotence, and light-headedness.

It is often necessary for blood pressure medication to be taken on a long-term basis and it is important not to stop taking the medication without medical advice. It is also necessary for the blood pressure to be regularly monitored to assess the effectiveness of treatment.


Lifestyle changes that reduce risk factors can reduce your risk of developing high blood pressure. Monitoring and early detection are also important.

It is generally recommended that adults over age 40 years should have their blood pressure checked regularly. It is also recommended that the following groups of people have their blood pressure checked regularly:

  • Those who have had a stroke, heart attack, high blood cholesterol, or diabetes
  • Those who have a history of high blood pressure
  • Those who are overweight
  • Pregnant women
  • Women taking oral contraceptive medications
  • Those who have a family history of high blood pressure or heart disease.

Further support

The Heart Foundation provides resources such as pamphlets and cookbooks and offers support and information to people with conditions such as hypertension and heart disease.

Contact details are as follows:

National Heart Foundation of New Zealand

Freephone: 0800 863 375


There are branches in most New Zealand regions. Consult the Heart Foundation website (‘Find a Branch’) or your local phone book for contact details.


Carretero, O.A, Oparil, S. Essential hypertension. Part I: definition and etiology. Circulation. 2000;101(3):329-35.

Heart Foundation (2019). Managing high blood pressure (Pamphlet). Auckland: National Heart Foundation of New Zealand.

Heart Foundation (Date not stated). Managing high blood pressure (Web Page). Auckland: National Heart Foundation of New Zealand. [Accessed: 28/11/22]

Mayo Clinic (2022). High blood pressure (hypertension) [Web Page]. Rochester, MN: Mayo Foundation for Medical Education and Research. [Accessed: 28/11/22]

Ministry of Health (2022). Annual Data Explorer – High blood pressure (diagnosed) 2021/2022 (Web Page). Wellington: New Zealand Government Ministry of Health.!/explore-indicators [Accessed: 28/11/22]

NHS (2019). High blood pressure (hypertension) (Web Page). Redditch: National Health Service (NHS) England. [Accessed: 28/11/22]

Last Reviewed: November 2022



The purpose of the Southern Cross Medical Library is to provide information of a general nature to help you better understand certain medical conditions. Always seek specific medical advice for treatment appropriate to you. This information is not intended to relate specifically to insurance or healthcare services provided by Southern Cross.