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Diseases > Complete Blood Count (CBC)

Complete Blood Count (CBC)

The complete blood count is a simple blood test. This test measures the number of cells in the blood.  It looks at the number of red blood cells, white blood cells, and platelets.

Red Blood Cells (RBC) or Hemoglobin

This test measures the amount of hemoglobin (HEE-mow-glow-bin).  Hemoglobin is important because it carries oxygen to the tissues. If there isn’t enough hemoglobin then the tissues don’t get enough oxygen.  There are many reasons hemoglobin might be low.

Here are a few of them:

  • Bleeding (this is obvious)
  • Iron deficiency (hemoglobin is made from iron)
  • Chronic diseases like rheumatoid arthritis can make it difficult for the bone marrow to make hemoglobin
  • In some autoimmune diseases (i.e. lupus) the immune system can actually attack and destroy red blood cells.
  • Finally, abnormal cells (cancer) in the bone marrow can make it difficult to make hemoglobin.

White Blood Cell Count (WBC)

This test measures the number of white blood cells in the blood.  White blood cells are important for fighting off infection.  There are five major types of white blood cells. Neutrophils (NEW-trow-fils) are very important in fighting off bacteria.  A very low number of neutrophils can increase the risk of infection.

Platelets (PLT)

This test measures the number of platelets. Platelets are very small sticky cells. Their job is to stop bleeding.

Low Platelets (Thrombocytopenia)

If there aren’t enough platelets it can be difficult to stop bleeding. There are many reasons that the platelets might be low.  A few examples include:

  • In some autoimmune diseases (i.e. lupus) the immune system can actually attack and destroy platelets.
  • Platelets can be trapped in the spleen
  • Too much alcohol can cause a reduction in platelets
  • Other medications can sometimes affect the platelet count
  • Finally, abnormal cells (cancer) in the bone marrow can make it difficult to make platelets.