It is important for you as a patient to understand the basics of what your lab results mean. This is especially important during treatment. I also recommend you keep a folder of your lab results handy whenever you call your doctor or see a new doctor.
The Complete Blood Count (CBC) is the most basic test to be familiar with, and is explained below. Additionally, a nice video showing the different types of cells in the CBC is at the following link: http://www.hematology.org/Publications/Videos/3917.aspx
Starting from the top (and only including relevant values):
WBC (White Blood Count): These little guys are your immune system defense system against bacteria and viruses. There are 5 different kinds of WBC’s, and you should mostly be concerned with the Neutrophil #. Neutrophils are the WBCs that defend against bacteria, and their numbers can take a dive during chemotherapy especially during Day 7-10 after chemotherapy. They can also become lower during radiation. What is dangerously low? Generally, a Neutrophil # less than 1.0 increases the risk of infection while less than 0.5 greatly increases the risk of infection.
Hemoglobin is the protein contained in red blood cells. This protein functions to carry oxygen to the body. When the hemoglobin is low this is “anemia”. Generally a hemoglobin <12-12.5 in a woman and <13-13.5 in a man is considered anemia. Anemia in cancer patients is often caused by the cancer itself and also by chemotherapy. Anemia related to chemotherapy is a controversial topic and is covered in the Transfusions vs Procrit/Aranesp page. Generally transfusions are given when the hemoglobin is <8 or Hematocrit is < 24, but this varies by patient, symptoms, and doctor. Note that both hemoglobin and hematocrit can go up when you are dehydrated and down when you are overhydrated.
HCT (Hematocrit) is how much space in the blood is occupied by red blood cells. It is a percentage. It is approximately equal to the hemoglobin x 3.
MCV (Mean corpuscular volume) measures the size of your red cells and it should be between 80-100. MCV provides easy clues to why a person may be anemic. In the example above, the MCV is <80 and the cause is iron deficiency.
Platelets help your blood clot and should be between ~130,000-450,000 (please multiply the number you see in your lab report by 1000). They can be low from chemotherapy, drugs, viral infections, bone marrow problems, a big spleen, or your own antibodies attacking your immune system. Platelets can be high from inflammatory states, low iron, and overgrowth of platelet stem cells in the bone marrow (“essential thrombocytosis”). Low platelets does not mean you will bleed spontaneously unless the platelet count is near 10,000 (unless you are on blood thinners). We will transfuse platelets into patients when they are somewhere between 1000 and 50,000 (the exact number depends on numerous factors). High platelets are usually not a problem until they are more than 1.5 million and then they can clump and cause clotting.