Understanding Your Blood Tests

Most people who come to our clinic do so either because they have a disease that directly affects their blood tests or have a disease such as lymphoma in which the blood tests may be affected by their treatment. This page provides a basic summary to give a basic understanding about the components of the blood.

When you bleed, or when you have blood taken, it initially appears to be an even red colour; however, if the blood is left standing on the bench the red blood cells fall to the bottom indicating that the blood is a mixture of several components. These components are:

Red blood cells carry oxygen. The blood test results include a range of numbers that describe different aspects of the red cells in your blood. The two most commonly used numbers are the haemoglobin (Hb) and the mean (or average) cell volume (MCV). The haemoglobin summarises how many red cells you have and gives an indicator of how much oxygen your blood can carry. If the Hb is low, you are anaemic.  If the Hb is high, you are polycythaemic. The mean cell volume (MCV) is influenced by many factors. For example, people with iron deficiency have small red blood cells and people with certain vitamin deficiencies can have large red blood cells.  The mean cell volume helps determine the cause of the anaemia or polycythaemia.

White blood cells help fight infection. The white cell count (WCC or WBC) gives the total number of white blood cells. This number is a combination of the 5 main white blood cell types - neutrophils, lymphocytes, monocytes, basophils and eosinophils. There are many causes of high or low white blood counts, but an important part of making a diagnosis is to determine which of the 5 white blood cell types are high or low.

The plasma contains clotting factors (that work with platelets to clot the blood), platelets and chemicals (for example salts, proteins, antibodies, enzymes from the liver and indicators of your kidney function).

Platelets are important in preventing and controlling bleeding and bruising. If platelets are low, there is an increased risk of bruising and bleeding. If platelets are high, there may be a higher risk of developing blood clots, including the blood clots that cause strokes and heart attacks.

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