Blood pressure categories – Australia
Blood pressure category	Systolic (mmHg)		Diastolic (mmHg)
Optimal	Less than 120	and	Less than 80
Normal	120-129	and/or	80-84
High-normal	130-139	and/or	85-89
Mild hypertension	140-159	and/or	90-99
Moderate hypertension	160-179	and/or	100-109
Severe hypertension	More than or equal to 180	and/or	More than or equal to 110
Isolated systolic hypertension	More than 140	and	Less than 90

Low blood pressure, or hypotension, is not as easy to define as it is usually relative to a person’s normal blood pressure reading, and varies between different people. It generally refers to a blood pressure below an average of about 90/60 mmHg.

Getting an accurate reading

According to the Heart Foundation, the diagnosis of high blood pressure should be based on multiple blood pressure measurements taken on separate occasions.

It is recommended that you do not smoke or drink caffeine-containing drinks for 2 hours before having your blood pressure monitored, as this can cause an increase in your readings.

Self-monitoring of blood pressure in your own environment (home blood pressure monitoring) or ambulatory monitoring of blood pressure is also used to help diagnose high blood pressure.

For ambulatory blood pressure monitoring, you wear a portable automatic blood pressure machine for 24 hours while going about your usual daily routine. The portable monitor will measure your blood pressure multiple times during the 24 hours. Your doctor will ask you to record your activities over the 24 hours, plus any symptoms you experience (and when they occur). Variations in blood pressure are normal and may occur depending on where and when the blood pressure is taken.

Some people who have raised blood pressure readings taken at the doctor’s surgery actually have acceptable levels outside the surgery, when under normal stress levels. This is known as ‘white-coat’ hypertension.

There are also people with ‘reverse white-coat’ hypertension (also known as masked hypertension), who have normal blood pressure when measured in the clinic but high ambulatory blood pressure readings (those recorded during normal daily activities).

Keeping on target

Your target blood pressure may vary according to whether you have other conditions that can increase your risk of cardiovascular (heart and blood vessel) disease or conditions that have been caused by high blood pressure.

Raised blood pressure is a major risk factor for cardiovascular disease, and the higher your blood pressure, the greater your chance of having heart disease or stroke. For this reason it is important that you have your blood pressure monitored regularly, and that you always take any high blood pressure treatments that have been recommended, including medicines that have been prescribed.

Hypertension can also be controlled to a large extent by lifestyle measures such as:

• losing excess weight;
• undertaking regular physical activity;
• quitting smoking; and
• changing your diet (reducing your alcohol and salt intake, and following a healthy eating plan).

These steps can help to lower your blood pressure and reduce your risk of cardiovascular disease.