quick read

Also known as

FBC; CBC (complete blood count); FBE (full blood examination); FBP (full blood picture); CBE; CBP

The Full Blood Count (FBC) is a group of tests performed on a single blood sample that tell us about the different kinds of cells in the blood.
 

When to get tested

The FBC is routinely ordered by doctors because it gives a useful overall picture of someone’s health. It is also used to help diagnose a range of specific health problems and to monitor treatments when they are known to affect blood cells.

Your doctor 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 important conditions.
 

Sample required

A blood sample drawn from a vein in your arm
 

Test preparation needed

None
 

What results can show

The FBC counts the number, types, shapes and sizes of the various cells in the blood, including:

  • Red blood cells (RBC), which carry oxygen around your body.
    The test measures red blood cell numbers, size and how much haemoglobin they contain. This can show if you don’t have enough iron or certain vitamins that are needed to make haemoglobin which takes oxygen to your tissues (anaemia).
  • White blood cells (WBC), which fight infection and play a role in immune responses such as inflammation and allergies.
    Looking at the various different types of white cells is called a WBC Differential. Each cell type has its own job to do in fighting infection. Some mainly fight against bacteria, others are involved in allergic responses, while others produce antibodies, especially against viruses. Increased numbers of certain WBCs can help to pinpoint if an infection is caused by a bacteria or virus. Some types of cancer (leukaemias) cause the body to make lots of one type of white cell, meaning the other cell types can’t be made properly.
  • Platelets, which are important in blood clotting.
    Low numbers of platelets can lead to excessive bruising or bleeding.


If some of your results are abnormal, the lab may go on to perform further testing in which a scientist or pathologist examines your blood under a microscope to look closely at the appearance of the blood cells, such as size, shape and colour to look for any abnormalities.

Your results will be presented as a series of numbers or measurements. Each blood component gives different information. Taken together, along with your symptoms and history, the results give your doctor important information. Some of your results may be higher or lower than normal when there is no problem. So, it’s important to talk with your doctor about what the results mean for your particular situation. For more details about results see our video.
 

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