What is being tested?

A full blood count test looks at the number, types and sizes of different cells in your blood:

• red blood cells, which carry oxygen around your body
• white blood cells, which fight infection
• platelets, which help blood to clot.

It also measures haemoglobin, the protein that carries oxygen around your body.

Why would I need this test?

A full blood count is a very common test used to screen for, help diagnose, and monitor a variety of conditions. It can be used as part of routine medical testing, or to examine specific issues such as:

• infection
• anaemia
• tiredness or weakness
• bleeding or clotting problems
• exposure to toxic substances
• monitoring response to treatment.

There are many medical conditions that can affect your full blood count. Some medications can also affect blood cells, and some vitamin or mineral deficiencies can impact red blood cells.

How to prepare for this test

No preparation is needed for this test.

Understanding your results

Many conditions change the numbers and proportions of various blood cell types in your blood. These changes can provide a great deal of information about your health. Here are some examples:

• Your red blood cells might be increased if too many are being made or you have lost fluid in your body. They might be decreased (anaemia), which can make you feel tired and weak.
• Infection and inflammation affect the number and types of white blood cells in the blood. Particular kinds and proportions of white blood cells can indicate specific conditions. Sometimes, diseases like leukaemia can make the white blood cell count very high.
• Bleeding and clotting disorders can affect the numbers of platelets in the blood.

There is a wide range of conditions and medications that can affect cell populations, so it is best to discuss your test results with your doctor.

More information

About full blood count testing

See Lab Tests Online for more information about a full blood count.

About blood testing

Visit our healthdirect‘s ‘Guide to blood testing’ to learn more about blood tests in general, including information about:

• what to consider before having a blood test
• what happens during a blood test
• results accuracy
• blood tests cost.