High blood pressure (Hypertension)

Understand high blood pressure, and its causes and symptoms.

High blood pressure (Hypertension)


What is high blood pressure?

High blood pressure, also known as hypertension, is when your heart has to work harder than normal to pump blood throughout the body causing an increased force exerted by the blood against the walls of the arteries. High blood pressure is typically measured in millimetres of mercury (mmHg) using two numbers: systolic pressure over diastolic pressure.

  • Systolic Pressure in the arteries is when the heart contracts and pumps blood out. It is the top number of a blood pressure reading—the 130 in 120/80 mmHg.
  • Diastolic Pressure in the arteries is when the heart is at rest between beats. It is the bottom number of a blood pressure reading—the 80 in 130/80 mmHg.

Everyone’s blood pressure is slightly different, and can vary depending on if your reading was taken at a GP surgery clinics or at home, but here is a general guide:

  • “>Normal (ideal): Between 90/60 mmHg and 120/80 mmHg
  • Elevated (at risk): Systolic between 120-129 mmHg and diastolic less than 80 mmHg
  • Hypertension Stage 1: Systolic between 130-139 mmHg or diastolic between 80-89 mmHg
  • Hypertension Stage 2: Systolic at least 140 mmHg or diastolic at least 90 mmHg (150/90mmHg or more if you are over 80 years old)
  • Hypertensive Crisis (seek immediate medical attention): Systolic over 180 mmHg and/or diastolic over 120 mmHg


There are two types of high blood pressure: primary hypertension and secondary hypertension. Primary hypertension (also known as essential hypertension) has no identifiable cause in most adults and develops over many years—usually along with plaque build-up in the arteries.

Secondary hypertension is caused by an underlying condition and tends to appear suddenly. Some causes of secondary hypertension are:

  • Adrenal gland tumours
  • Congenital heart defects (blood vessel problems present at birth)
  • Cough and cold medicines containing pseudoephedrine or phenylephrine, some pain relievers, birth control pills, and other over-the-counter or prescription drugs
  • Illegal drugs, particularly stimulants like cocaine and amphetamines
  • Kidney disease
  • Obstructive sleep apnoea
  • Hormone disorders or thyroid problems
  • Stress—did you know that sometimes just getting nervous at the doctor’s office can cause your blood pressure to rise? It’s so common it has a name: white coat hypertension.


Many people with high blood pressure but don’t realise they have it—what is often considered a “silent” condition—because it typically does not cause noticeable symptoms, even if their blood pressure readings reach dangerously high levels. The only way to find out if your blood pressure is high is to have your blood pressure checked.

A few people with high blood pressure may experience:

  • Headaches, particularly in the back of the head or base of the skull
  • Shortness of breath, during physical activity or even when laying down
  • Nosebleeds
  • Vision changes, blurriness or seeing spots
  • Chest pain (angina), especially during stress or physical exertion
  • Fatigue, weakness or dizziness

In advanced stages, high blood pressure can lead to life-threatening heart attacks and strokes.

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