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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. For more articles go to the Medical Library index page.

High blood pressure - hypertension

High blood pressure is a common medical condition in which the pressure exerted by the blood on 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 1 in 5 New Zealanders and is a significant contributor to the incidence of heart disease and stroke .  High blood pressure is preventable and treatable, through lifestyle changes and medications.  

General information

As blood travels around the body it exerts pressure against the artery walls.  A blood pressure reading is a measurement of this force.  There are two components to a blood pressure reading, both of which are measured in millimetres of mercury (mmHg).  The higher number is the “systolic” reading and is the pressure in the arteries as the heart beats (contracts) to force the 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.   
Blood pressure varies throughout the day in response to factors such as excitement, stress and exercise.  However, it quickly returns to a normal level. Blood pressure also increases with age, so what may be a normal blood pressure reading for someone in their 60's may be considered abnormally high for someone in their 20's.
An ideal blood pressure for most people is less than 130/80 mmHg.  In general, hypertension is defined as having blood pressure of 140/90 mmHg or higher.

Signs and symptoms

There are usually no signs and symptoms of hypertension until the condition has been present for a long time – sometimes for many years. Because of this, many people are not aware that they have hypertension.  It is advisable, therefore, to have blood pressure measured regularly, such as during a routine doctor's appointment.
Over time, the continuous high pressure of blood puts extra strain on the blood vessels and internal organs.  Often people do not consult a doctor until after the condition has progressively caused damage to the blood vessels and internal organs (particularly the heart and kidneys). For this reason hypertension has been referred to as the “silent killer”.  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 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” hypertension.  In the other 5% of cases hypertension is due to specific factors such as kidney disease or various gland disorders and is called “secondary” hypertension.  In these cases, treating the underlying cause will often relieve the hypertension.
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.
It is difficult to predict who will develop hypertension but there are a number of known risk factors for the condition, the most important of which is being overweight.
Known risk factors include:  
  • Being overweight
  • 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
  • Excessive caffeine intake (eg: coffee, tea and some soft drinks)
  • Use of oral contraceptive medications
  • Certain chronic medical conditions, e.g. kidney disease, diabetes and sleep apnoea.


For a diagnosis of hypertension to be made the blood pressure must remain elevated for several readings over a period of time.  If the blood pressure remains elevated the doctor may also order blood tests, urine tests, an ECG (tracing of the heart's electrical activity), a chest x-ray 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, other medical conditions and risk factors. 
In general, treatment of hypertension will focus on two main areas – lifestyle changes and medications. If the blood pressure is not significantly elevated the doctor may initially recommend lifestyle changes in an attempt to lower the blood pressure. The blood pressure will be regularly monitored for any improvement. However if lifestyle changes alone do not adequately lower the blood pressure within a 3-6 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 the blood pressure to an acceptable 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.
  • ACE inhibitors (e.g. cilazapril) work by blocking the formation of a particular chemical in the blood.  This helps to dilate blood vessel walls and reduce salt and water retention in the body and so decreases 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 inform the doctor of any other medical conditions and any other medications being taken.  It is also important to inform the doctor of any side effects experienced whilst taking the 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 extremities, 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 in order to assess the effectiveness of treatment.


While high blood pressure cannot necessarily be prevented, reducing risk factors can reduce the risk of developing it. Monitoring and early detection are also important.

It is generally recommended that men over 45 years of age and women over 55 years of age should have their blood pressure checked regularly.  It is also recommended that the following groups of people have their blood pressure checked regularly: 

Further support

The Heart Foundation of New Zealand 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:
The Heart Foundation of New Zealand
Mail: PO Box 17 160, Green Lane, Auckland
Phone: 0800 863 375
There are branches in most New Zealand regions. Consult your local phone book for contact details.


O’Toole, M.T. (Ed.) (2013). Hypertension. Mosby’s Dictionary of Medicine, Nursing & Health Professions (9th ed.). St Louis, MI: Elsevier Mosby.
Mayo Clinic (2016). High blood pressure (hypertension) [Web Page]. Rochester, NY: Mayo Foundation for Medical Education and Research. [Accessed: 27/02/17]
Heart Foundation of New Zealand (Date unknown). Managing high blood pressure (Web Page). Auckland: The National Heart Foundation of New Zealand. [Accessed: 27/02/17]

Last Reviewed – February 2017



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