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Alternative Names
full blood count, complete blood count

A FBC, also called a full blood count, is a screening test used to diagnose and manage many diseases. A FBC measures the status of important features of the blood, including the:
  • number of red blood cells (RBCs)
  • number of white blood cells (WBCs)
  • number of platelets
  • total amount of haemoglobin in the blood
  • percentage of blood composed of cells, or haematocrit
  • mean corpuscular haemoglobin (MCH)
  • mean corpuscular haemoglobin concentration (MCHC)
  • mean corpuscular volume (MCV)
Who is a candidate for the test?
A FBC is a part of routine blood testing done with physical examinations. It is also used to help diagnose many disorders, including problems with a person's blood, heart, kidney and nutritional status.

How is the test performed?
A blood sample is taken from a vein on the forearm or hand. First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube, or "tourniquet," is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A fine needle is gently inserted into a vein, and the tourniquet is removed. Blood flows from the vein through the needle, and is collected in a syringe or vial. After the needle is withdrawn, the puncture site is covered with a bandage for a short time to prevent bleeding.

What is involved in preparation for the test?
A person should request specific instructions from his or her doctor.

What do the test results mean?
Normal values are:
  • RBC (value changes with altitude): Male, 4.7 - 6.1 million cells/uL (cells per micro litre); female, 4.2 - 5.4 million cells/uL (cells per micro litre)
  • WBC: 4.0 - 11.0 thousand cells/uL (cells per micro litre)
  • haematocrit (varies with altitude): Male, 40.7-50.3%; female, 36.1-44.3%
  • haemoglobin (varies with altitude): Male, 135 - 180 g/L; female, 115 - 160 g/L
  • MCV: 80-98 femtolitre
  • MCH: 27-35 pg/cell
  • MCHC: 32-36 gm/dl
Abnormally high numbers of red blood cells may indicate:
  • low oxygen tension in the blood.
  • congenital heart disease, or a heart condition that a person is born with.
  • cor pulmonale, a condition in which the right lower part of the heart becomes swollen.
  • pulmonary fibrosis, or hardening of the lung tissue, which can make breathing difficult.
  • dehydration, or lack of fluid in the body. This can occur with conditions such as severe diarrhoea.
  • kidney disease with high erythropoietin production. Erythropoietin is a hormone made in the kidney.
Abnormally low numbers of red blood cells, or anaemia, may indicate:
  • blood loss
  • haemorrhage, or loss of blood
  • bone marrow failure
  • erythropoietin deficiency, which occurs when the kidney does not produce enough of the hormone
  • haemolysis, or the destruction of RBCs from a transfusion reaction
  • leukaemia, or cancer of the blood and bone marrow
  • multiple myeloma, a cancer of the bone marrow
  • malnutrition
  • over hydration, or absorption of too much fluid
Abnormally low numbers of white blood cells may indicate:
  • bone marrow failure
  • the presence of substances toxic to cells
  • collagen-vascular diseases, which are any diseases that cause the small blood vessels and tissue to swell
  • liver or spleen disease
  • exposure to radiation
High numbers of white blood cells may mean:
  • infections
  • inflammatory diseases
  • leukaemia
  • emotional or physical stress
  • tissue damage
High haematocrit may indicate:
  • dehydration.
  • burns.
  • diarrhoea.
  • eclampsia. Eclampsia is a serious condition involving high blood pressure, protein in the urine and swelling of the face and hands during pregnancy. It can lead to seizures and coma.
  • erythrocytosis, or an abnormal rise in the number of red blood cells.
  • polycythemia vera, or an increase in the cell mass or red blood cell levels in the blood.
  • shock.
Low haematocrit may indicate:
  • anaemia
  • blood loss
  • bone marrow failure
  • haemolysis, or the separation of haemoglobin, the oxygen-carrying component of red blood cells, from the red blood cells
  • leukaemia
  • malnutrition
  • specific nutritional deficiency
  • multiple myeloma
  • over hydration
  • rheumatoid arthritis, a long-term disease in which the connective tissue is destroyed
Low haemoglobin values may indicate:
  • anaemia
  • blood loss
Author: David T. Moran, MD
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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