The role of the RBCs is to carry oxygen throughout the body to different tissues. The percentage of RBCs in the blood is called the hematocrit. The part of the RBC that carries oxygen is a protein called hemoglobin. Anemia occurs when there is a decrease in the number of RBCs in the body. Anemia is detected by looking for a low hemoglobin level or a low hematocrit. Normal hemoglobin ranges between 12 and 16 g/dl (or a hematocrit of 40-50%). Most people will have some symptoms when the hemoglobin is less than 8. This is why blood transfusions are frequently ordered when the hemoglobin is less than 8. The role of the WBCs is to defend the body against infections. The neutrophils (one subtype of WBC) kill most regular bacteria. Lymphocytes are responsible for killing viruses and constitute an important part of the immune system. Infections are therefore more likely to occur when the WBCs is low. Normal WBC count is 3,000 to 9,000/mm3. The Absolute Neutrophil Count (ANC) is used to measure the amount of neutrophils you have to fight infections. You can figure out your ANC by multiplying the total number of WBCs by the percentage of neutrophils. Serious infections are more likely to occur when your ANC falls below 500. Your WBC will generally fall within the first week after starting chemotherapy. Most people recover their WBC count 21 to 28 days after starting chemotherapy. Platelets are the cells that help control bleeding. The normal platelet count is 150,000- 300,000/mm3. The risk of bleeding increases when the platelet count is less than 10-20,000. Platelet transfusions are usually administered when the platelet count is lower than 10-20,000/mm3. The risk of bleeding increases if you have taken aspirin, Motrin, Advil or other anti-inflammatory drugs. Tylenol has no effect on platelets.