What is a full blood count?

A full blood count (FBC) is a common blood test. It checks different types of blood cells to help find signs of infections, blood disorders or other health conditions. An FBC looks at the size, shape and colour of:

• red blood cells
• white blood cells
• platelets

It's also called a complete blood count (CBC) or full blood examination (FBE).

Red blood cells

Red blood cells carry oxygen around your body. An FBC also measures:

• haemoglobin — the protein in red blood cells that carries oxygen
• haematocrit — how much of your blood is made up of red blood cells
• mean cell volume (MCV) — the average size of your red blood cells
• mean cell haemoglobin (MCH) — how much haemoglobin is in each red blood cell
• mean cell haemoglobin concentration (MCHC) — how concentrated the haemoglobin is inside red blood cells

White blood cells

White blood cells protect your body from infections. Different types include:

• neutrophils — fight bacteria and viruses
• lymphocytes — help your immune system and make antibodies
• monocytes — break down germs and dead cells
• eosinophils — fight parasites and are involved in allergic conditions
• basophils — release chemicals that help control immune responses

Your doctor may want to check these levels to look for infections, inflammation or immune system problems.

Platelets

Platelets are tiny cell fragments that help blood clot. When you get a cut, platelets stick together to form a clot and stop the bleeding. An FBC measures how many platelets you have in your blood.

When is a full blood count used?

A full blood count helps check your overall health. It can be used to diagnose, monitor or screen for medical conditions. It is also often done as part of a routine health check.

Your doctor may refer you for an FBC to check for:

• infections
• anaemia or other blood disorders
• bleeding or blood clotting problems
• exposure to toxic substances or chemicals, such as lead poisoning
• how your body is responding to a medicine
• vitamin or mineral deficiencies
• cancers and cancer-related side effects

An FBC may also help look for other health issues. It may be used together with other tests to confirm a diagnosis of some health conditions.

Where can I get a full blood count?

You usually need to go to a pathology collection centre with a referral from your doctor. Your doctor will recommend one near you.

Sometimes, your doctor will collect blood for testing in their clinic. Blood tests are also routinely done in hospitals.

How do I prepare for a full blood count?

There is no special preparation needed for a full blood count.

However, if you are having other blood tests done at the same time, you may need to prepare. Check with your doctor or the pathology collection centre if there is anything you need to do before your blood test.

There are also some things you can do to make it easier for your blood collector to find a vein.

What happens during a full blood count?

A full blood count is usually done at a pathology collection centre. A health professional will take a sample of blood, usually from a vein in your arm. The blood will then be sent to a laboratory for testing.

What do my full blood count results mean?

Ask your doctor what your FBC results mean in your situation.

Some results are compared to reference intervals or ranges. These are a range of values that are considered generally normal for the population, but not necessarily for everyone.

If your results are higher or lower than what is considered normal for the general population, it doesn't always mean there is a problem. Your doctor will explain what they mean for you and if you need more tests.

Red blood cells

Red blood cells carry oxygen. If you have too few red blood cells, your body may not be getting enough oxygen, which could be a sign of anaemia.

If you have too many red blood cells, your blood may become thicker, increasing the risk of blood clots.

White blood cells

White blood cells help fight infections.

• A high count may mean your body is fighting an infection.
• A low count may suggest an autoimmune condition or be due to a medicine you are taking that lowers your immune system.
• Abnormal levels may also suggest inflammation or a blood disorder.

Platelets

Platelets help blood clot. A low count may cause easy bruising or excessive bleeding. A high count may increase your risk of blood clots.

You should always discuss your blood test results with your doctor to understand what they mean for you.

Resources and support

Pathology Tests Explained provides information about full blood count tests.

Read our 'Guide to blood testing' to learn more about blood tests, including:

• what to consider before having the test
• what happens during a blood test
• how accurate results are
• blood test costs

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