The number of white blood cells may go up it may be because of a bacterial infection, bleeding or a burn. More rarely the cause of a raised white count is due to leukaemia , cancer or malaria. A person may lose white blood cells because they have autoimmune problems - this is where the antibodies that should fight diseases attack the body instead. Other reasons for loss of white blood cells include viral infections. More rarely, this can be a side effect of certain kinds of medication.
Doctors keep an eye on white blood cells to work out how a disease is changing.
By monitoring the blood count in this way they can alter the patient's treatment as necessary. They form the basis of the blood clot which would form if you cut yourself . Low numbers of platelets can make a person vulnerable to bleeding, sometimes even without injury occurring. Causes of low platelet counts include autoimmune diseases where you produce an antibody to your own platelets, chemotherapy, leukaemia, viral infections and some drugs. High numbers of platelets make a person more vulnerable to blood clots.