Medical Q&As

Full blood count - explain?

My doctor recently sent me for a blood test because he said that I looked a little pale. The test is called an FBC. What does that mean and what would it show up?

The letters FBC stand for full blood count. It is a very useful test and is one of the most frequently performed tests in the hospital laboratory. The test is performed in a special automated analyser that gives a report on various indices in the blood. A 5 ml (teaspoonful) sample of blood is all that is required. I suspect that your doctor is requesting this test because he suspects that you are anaemic, which usually means that your blood is low in iron. The FBC result will confirm if you are anaemic and may even give clues as to the cause of the anaemia. Iron deficiency is the commonest cause of anaemia but it may sometimes occur as a result of deficiency in certain vitamins such as B12. The test gives such varied information as the number of red cells in your blood as well as the number of platelets and white cells. It will also indicate the size of the red cells and also the amount of haemoglobin in your blood. Haemoglobin is the oxygen carrying protein in the blood and the level of this compound is reduced in the case of anaemia. If abnormalities are present in the FBC the laboratory technician will often proceed to perform a blood film, which involves smearing a small amount of blood on a glass slide and examining the cells with the aid of a high powered microscope. In summary the FBC gives information on the size, shape, colour and quantity of the various cell elements that form the blood. It can be considered to be a useful measure of the state of health of the blood itself.