Full Blood Count (FBC, Full Blood Test or Complete Blood Count, CBC)

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What is a full blood count and why is it done?
How is an FBC performed?
Preparing for an FBC
What happens during an FBC?

What is a full blood count and why is it done?

A full blood count (FBC) is a very common clinical procedure and often the "starting point" for most medical investigations. An FBC not only tests for disorders and abnormalities of the blood but, as blood travels throughout the whole body, it can give an indication of disease present in other organs.

An FBC, as the name suggests, is used to obtain a count of the blood cells in the sample of blood taken. The counts from this small sample are used to estimate the levels of different blood cells within your body’s blood system.

Blood is made up from three main types of blood cell: red blood cells, white blood cells and platelets. The number of cells present, the size and proportions of these cells, and the haemoglobin level are measured in an FBC. Haemoglobin is the oxygen carrying component of red blood cells.

How is an FBC performed?

A blood test can be carried out by your doctor, or you will be sent to a pathology centre where other health care professionals, such as a nurse, will perform the procedure. The full blood count is a very quick procedure, usually only 5 minutes!

Preparing for an FBC

There is no preparation necessary for a full blood count. It can be done at any time of the day.

However, if the blood test will be used not only for a blood count but for other reasons (e.g. glucose or cholesterol monitoring), you will be required to fast beforehand. Therefore, these tests are better done in the morning.

What happens during an FBC?

Procedure

You are required to sit upright in a chair and rest your arm face up on an elevated arm rest. The clinician will tie a strap (tourniquet) around the top of your arm to temporarily restrict the blood flow from your arm back to your heart. This will make the vein inside your elbow "pop out", and therefore easier to find. The area where the needle will be inserted is wiped with a sterile alcohol wipe to reduce any risk of infection. A needle is inserted into the vein and a small amount of blood is drawn into the vial attached to the needle.

If seeing blood makes you queasy, it is best to look away. You may like to bring some jelly beans with you to suck on after the procedure in case you feel faint. Usually the clinician will ask you questions as they take the blood to distract you from the procedure. It is done in no time! If there is any pain at all, it is minimal. More often than not, you will only feel a slight discomfort.

After the procedure, the clinician will press a small wad of cotton on the entry point to stop the flow of blood. The cotton wad is strapped on with a bandaid. This only needs to remain on for a couple of hours. Sometimes a little bruise is left in this spot, but this is nothing to worry about.

The FBC for children

There is very little difference between children's veins and adult veins. Therefore the procedure is very similar. Children can be quite scared of needles, though, so it is important that the parent and medical practitioner both encourage the child to remain calm and relaxed. You may wish to explain to the child that it only stings for a very short time, and offer them a treat afterwards.

Blood sample analysis

The analysis of the collected blood is carried out automatically by a machine in a pathology laboratory. The laboratory will send the results to your doctor. You will be able to call up for your results after approximately 5 days.

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