What is low blood pressure?

Low blood pressure is also known as hypotension.

Hypotension is any blood pressure that is lower than expected for you.

Many healthy, young adults can have a resting blood pressure that is relatively low. But low blood pressure can also be caused by serious illness and other health conditions.

What is blood pressure and how is it measured?

Blood pressure is the force that keeps blood moving through your arteries (blood vessels) after it leaves your heart. Blood pressure is measured in millimetres of mercury (written as mmHg).

An example of a blood pressure reading is '120 over 80'. This is written as 120/80mmHg. The 2 numbers refer to:

1. Systolic blood pressure is the pressure as your heart pumps blood through your arteries — the top number.
2. Diastolic blood pressure is the pressure in your arteries when the heart relaxes between beats — the bottom number.

Your blood pressure changes throughout the day depending on many factors, including your general health and activity levels.

What symptoms are related to low blood pressure?

Symptoms of low blood pressure can include:

• lightheadedness or dizziness
• weakness
• blurry vision or dimmed vision
• pale, clammy skin
• nausea
• fatigue
• fainting

Orthostatic hypotension, or 'postural hypotension', is when your blood pressure drops when you stand up after sitting or lying down. This can cause symptoms of lightheadedness. Your symptoms will usually improve if you sit or lie back down.

Sometimes, there are no symptoms with hypotension. Low blood pressure may be picked up during a medical examination.

What causes low blood pressure?

Some causes of low blood pressure are:

• dehydration
• anaemia
• heart failure and other heart conditions
• pregnancy
• certain medicines
• autonomic neuropathy — problems with how your body controls your blood pressure, which can be due to conditions such as diabetes and nervous system conditions
• some hormonal conditions

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

• a severe allergic reaction — anaphylaxis
• being seriously ill with an infection — such as sepsis
• blood loss (such as from trauma or gastrointestinal bleeding)

How is the cause of low blood pressure diagnosed?

Your doctor will ask about your symptoms and examine you. They will want to know about your:

• general health
• family history
• lifestyle
• what medicines you are taking
• if you have any allergies
• if you know your previous blood pressure readings

Your doctor will measure your blood pressure. They may take your blood pressure and heart rate while you are lying down and standing up.

Your doctor will consider your background, current symptoms and overall health when working out if your blood pressure is normal for you or too low. Your doctor may ask you to:

• check your blood pressure at home
• wear a blood pressure monitor over a 24-hour period

They may recommend some tests, such as:

• blood tests
• urine tests
• an electrocardiogram (ECG)
• imaging tests

When should I see my doctor?

Many people have mild symptoms of low blood pressure from time to time, often when standing up from sitting or crouching. You should see your doctor if your symptoms:

• are new
• have come on suddenly
• have changed
• happen while you are lying or sitting
• are more frequent or more severe

When to seek urgent care

Call an ambulance or go to a hospital emergency department if you have symptoms of low blood pressure and:

• chest pain
• breathlessness
• a racing heart
• a fever
• a recent injury

How is low blood pressure treated?

Treatment for low blood pressure depends on the cause.

Treatment of emergency conditions

Low blood pressure due to emergency health conditions needs immediate hospital treatment. Depending on the cause, this may involve:

• oxygen
• intravenous fluids (fluid through a drip into a vein)
• a blood transfusion
• medicines

Self-care and medicines for orthostatic hypotension

If you have orthostatic hypotension that is ongoing, your doctor may recommend you:

• adjust your salt intake
• drink plenty of water, especially early in the day
• limit how much alcohol you drink
• change your medicines
• wear compression stockings or a special belt or binder around your abdomen (tummy)
• take part in a special exercise program

Your doctor may advise you to take precautions to prevent episodes of low blood pressure, such as avoiding:

• dehydration
• hot showers
• hot environments
• standing up too quickly
• standing for long periods of time

If you feel lightheaded, sitting or lying down should help relieve your symptoms.

Take it slowly and sit first when moving from lying down to standing.

What are the complications of low blood pressure?

Orthostatic hypotension can cause fainting and increase your risk of falls.

Some people with orthostatic hypotension can have high blood pressure at night while lying down.

Can low blood pressure be prevented?

In people with a higher risk of orthostatic hypotension, it may help to:

• avoid certain medicines that can lower your blood pressure
• make sure you are always well hydrated and avoid dehydration
• avoid very low salt diets
• keep your blood glucose levels well controlled if you have diabetes

Resources and support

You can call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with you 24 hours a day, 7 days a week.