Your doctor orders an Red blood cell count (RBC) to determine if the number of red blood cells in your body is low (called anemia) or high (called polycythemia). Your doctor may also learn about the size and shape of your red blood cells from an RBC.

Common causes of an abnormal RBC could be: Anemia Iron deficiency anemia, most often due to chronic blood loss (e.g., menstruation, small amounts of bleeding due to colon cancer); occasionally due to a diet lacking iron . Acute blood loss (e.g., acute bleeding ulcer, trauma) Hereditary disorders (e.g., sickle cell anemia, thalassemia). Polycythemia is an excess of red blood cells and is uncommon.

Hematocrit - A hematocrit is another way to determine whether your red blood cell count is high, low, or normal. The hematocrit measures how much of your blood is made of red cells. A hematocrit can be done by pricking your finger with a needle and drawing a drop of blood up into a glass tube, which looks like a small straw. This is easier and faster and is often done on children because it doesn't hurt as much.

Hemoglobin test - Hemoglobin is a protein found in red blood cells. It gives blood its characteristic red color. It is the protein that combines with oxygen from your lungs and carries the oxygen to cells throughout the body. When a person has a low hemoglobin level, he or she usually also has a low red blood cell count and a low hematocrit.

Common causes of an abnormally low hemoglobin: anemia iron deficiency anemia, which may be caused by an diet poor in iron-containing foods loss of blood through internal bleeding, such as an ulcer, or external bleeding, such as trauma

White blood cell count (WBC) - Normally, there are far fewer white cells than red cells in the blood. You may remember this image, of the bone marrow of a person suffering from Leukemia, from our study of Cancer. The cellular portion of this person's bone marrow is almost exclusively white blood cells. When you have an infection, you may have increased numbers of white blood cells.

The white blood cells are sent from the bone marrow to attack the bacteria or virus that is causing the infection. A low white blood cell count makes it harder for your body to fight off an infection. People with a low white blood cell count are more likely to catch colds or other infectious diseases and are said to be immuno-compromised

Differential blood cell count - White blood cells come in several shapes and sizes. The different types of white blood cells can be identified by examining a blood sample under a microscope.

As we have noted there are five different kinds of white blood cells. Your doctor orders a differential blood count in order to help make a diagnosis. A high Eosinophil count often indicates allergies, skin diseases, or parasitic infections. A low Lymphocyte count may be seen in AIDS. A high Monocyte count usually indicates an infection, often one caused by bacteria. A high Neutrophil count is seen in infections, some cancers, arthritis, and sometimes when the body is under stress (for example, after surgery, trauma, or a heart attack. Immature (or young) white cells of all types may be seen in bacterial infections and leukemia.

White Blood cell (Leukocyte) Identification

Platelet count - Platelets are the cells/particles found in the blood. Platelets help stop bleeding after an injury by gathering around the injury site, plugging the hole in the bleeding vessel and helping the blood to clot more quickly. Platelet counts are often done if you are prone to bruising or if you are about to have surgery. A low platelet count is called thrombocytopenia. Common causes of a low platelet count include: undergoing cancer treatment, some leukemias, certain types of cancer, and in some immune system disorders the body will sometimes destroy its own platelets.

T- and B- cells are the major players in your Immune System