Summary

• The Full Blood Count (FBC) is a routine test that can be used to assess your general health or to check for a variety of disorders that affect blood cells.
• It counts and measures the different cells in your blood, including red blood cells, white blood cells and platelets.
• Each of these have specific functions and assessing them can give important information. 

What is your blood made of?

Your blood is made up of Red Blood Cells (RBCs), White blood Cells (WBCs) and platelets. These float in fluid called plasma.

The solid part of blood

Red blood cells (RBC)

These contain haemoglobin which carries oxygen to all tissues of the body. The scientific term is erythrocytes.

White blood cells (WBC) 

There are five types of WBCs all with different functions:

• Neutrophils are the most common type of circulating WBCs. They move to damaged or infected tissue in the body to engulf and destroy any bacteria.
• Monocytes are similar to neutrophils.  They migrate to the site of an infection and engulf and destroy any bacteria.
• Eosinophils respond to infections caused by parasites, play a role in allergic reactions, and control the extent of immune responses.
• Basophils are the least common WBC and are involved in allergic reactions.

Lymphocytes

These can be found in the lymphatic system (which drains excess fluid from the body and blood) and are subdivided into three types:

• B lymphocytes (B cells) produce antibodies as part of the immune response,
• T lymphocytes (T cells) recognise foreign substances and processes them for removal, and
• Natural Killer cells (NK cells) directly attack and destroy cancerous cells or cells infected with a virus.

Platelets 

These are essential for normal blood clotting. They help stop bleeding by forming together to create a temporary plug in broken blood vessels.

The liquid part of blood

Plasma

This is a pale-yellow liquid that represents about half of the content of whole blood. It contains water, salt and proteins that help blood to clot, transport nutrients, minerals and hormones throughout your body.  

Blood cells are continually being renewed

Blood cells are constantly being renewed. New cells are continuously being produced in the bone marrow, the soft fibrous tissue inside many bones. Blood-forming stem cells are made in the bone marrow, which is the spongy material inside your bones. RBCs stay and mature here until needed and then are released into the blood. Red cells live for about 120 days, platelets live for about six days, and the lifespan of white blood cells depend on the type – from only a few hours to many years.

If you have an infection or inflammation somewhere in your body, the production of white cells goes up. The WBCs are released from the bone marrow, travel in the blood to the site of infection or inflammation and when they have completed their task, the bone marrow stops or reduces their production.

Why get tested?

The FBC helps to screen, diagnose, and monitor a wide range of disorders and conditions such as anaemia, blood clotting problems, infections, blood cancer and immune system disorders.  

What does the FBC examine?

Each test in the FBC gives different information. Looked at together, along with your symptoms and medical history, they help build a picture of the health of your blood.

Having the test

Sample
Blood.

Any preparation?
None.

Your results

Reading your test report

Your results will be presented along with any other tests your doctor ordered on the same form. You will see separate columns or lines for each of these tests.

Reference Intervals
The results of each component will be compared to reference intervals (sometimes called a normal range).

• Reference intervals are the range of results expected in healthy people.
• If your result is outside this range, it can be flagged as high (H) or low (L) if they sit outside this range.
• Many reference intervals vary between labs so only those that are standardised or harmonised across most laboratories are given on this website.

If your results are flagged as high or low this does not necessarily mean that anything is wrong. It depends on your personal situation and your results need to be interpreted by your doctor.

Further tests
The FBC is performed on laboratory analysers that automatically count the different components. If some of your results are unclear, the laboratory may go on to perform further testing in which a scientist or pathologist examines your blood under a microscope. They look more closely at the appearance of the blood cells, such as size, shape and colour, searching for any abnormalities. Your doctor may want you to have other tests to help confirm a diagnosis. Also, they may decide to check on your FBC from time to time because changes in the number of the different cells can be caused by many different illnesses.

Questions to ask your doctor

The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help. 

You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely. 

Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements, as these may affect your results. Ask:

• Why does this test need to be done?
• Do I need to prepare (such as fast or avoid medications) for the sample collection?
• Will an abnormal result mean I need further tests?
• How could it change the course of my care?
• What will happen next, after the test?

Any more to know?

There is no way you can directly raise the number of your WBCs or change the size or shape of your RBCs. Addressing any underlying diseases or conditions and following a healthy lifestyle will help optimise your body's cell production and your body will take care of the rest.

More Information

Pathology and diagnostic imaging reports can be added to your My Health Record.

You and your healthcare provider can now access your results whenever and wherever needed. Get further trustworthy health information and advice from healthdirect.