When the heart is squeezing blood into the arteries, the pressure is high. When the heart is relaxed, the pressure is lower.

Your blood pressure is a measurement taken of the highest reading and the lowest reading. It is given as 2 figures — highest over lowest. Blood pressure is measured in ‘mmHg’, which refers to millimetres of mercury.

What is low blood pressure?

Low blood pressure is also known as hypotension.

Most doctors would say that you have low blood pressure if it is below 90/60 mmHg. Your doctor will refer to this as ‘90 over 60’.

Is low blood pressure a problem?

For some people, low blood pressure is a sign of good health. These are generally people who are very fit and who have a slow pulse. For other people, low blood pressure is a problem.

Often, people with low blood pressure can be expected to lead longer lives.

However, people who experience continuing symptoms of low blood pressure should see a doctor. Sudden, severe low blood pressure (shock) can be associated with serious medical conditions.

What are the signs and symptoms of low blood pressure?

The symptoms of low blood pressure may include:

• light-headedness
• dizziness
• weakness
• blurry vision
• pale, clammy skin
• fatigue
• fainting

These symptoms can occur when doing nothing. They are more likely to occur when changing position, such as standing up or when straining on the toilet.

However, often there are no symptoms and low blood pressure is often only identified as a result of a routine medical examination or during the course of an investigation for some other condition or underling illness.

Low blood pressure may be more serious in elderly people who may have an underlying illness or who may be at risk of a fall.

Check your symptoms with healthdirect’s Symptom Checker to get advice on when to seek medical attention.

What causes low blood pressure?

Apart from being very fit, people can have low blood pressure if they:

• are overheated, either from the weather, from hot baths or showers, or from wearing too many clothes
• have too little blood circulating, either from donating blood, from bleeding heavily, or from being dehydrated
• are pregnant
• are taking one of many different types of medicines
• have a lot of drugs or alcohol in the system

People can also have low blood pressure due to medical conditions, such as if they:

• are having an allergic reaction
• are seriously ill with an infection
• have certain heart conditions
• have a disorder of the nervous system or glandular (endocrine) system
• are in severe pain
• have nutritional deficiencies

There is also a particular type of low blood pressure called ‘postural hypotension’ or ‘orthostatic hypotension’. In this condition, a person’s blood pressure is normal when they are sitting or lying down, but it drops suddenly when they stand, making them feel dizzy or lightheaded. This can also occur when standing too long without moving.

Postural hypotension is fairly common, particularly in older people. It can be caused by one of the situations or conditions listed above. If it happens often, or if it causes problems, you should see your doctor about it.

When should I see a doctor?

If you think you might have symptoms of low blood pressure listed above, it’s best to see your doctor.

How is low blood pressure treated?

If there is an underlying cause for your low blood pressure, and it is giving you problems, you may need treatment for that underlying cause. But if it isn’t causing you problems, treatment won’t be needed.

Your doctor may advise you to take precautions to prevent episodes of low blood pressure, such as avoiding dehydration, hot showers or standing up too quickly.