CBC measures the number of three types of cells in your blood:
- Help diagnose other blood cancers, such as leukemia and lymphoma
- Find out if the cancer has spread to the bone marrow
- See how the human body reacts to cancer treatment
- Find other conditions, other than cancer
If you receive chemotherapy, your doctor may check your blood cell count more often using CBC.
What does a complete blood count measure?
CBC measures the number of three types of cells in your blood:
Number of white blood cells. The number of white blood cells, also called leukocytes, measures the total number of white blood cells in a blood sample. These cells protect the body from infection by attacking invading bacteria, viruses, and other foreign substances in the body. Some white blood cells can also attack cancer cells.
Differences in white blood cells. The difference in white blood cells measures the amount of each type of white blood cell. There are five major types of white blood cells, and each type plays a unique role in the body's defenses. Your doctor can read important information about your health by measuring the levels of these cells:
- Neutrophils
- Lymphocytes
- Monocytes
- Eosinophils
- Basophils
Red cell count. Red blood cells carry oxygen throughout your body. The number of red cells, also called erythrocyte counts, measures the number of red blood cells in a blood sample. There are several ways to measure red blood cells. The two most common are:
- Hematocrit (Hct), the percentage of your blood that is made up of red blood cells
- Hemoglobin (Hgb), a protein in red blood cells that carries oxygen
- Platelet count. Platelet count measures the number of platelets in a blood sample. Platelets help stop bleeding by forming blood clots.
The values for each of these types of cells have a standard range. Your healthcare team will see this distance in your CBC lab results. Width is used instead of a specific number because the standard value varies from person to person.
What do the results mean?
Your healthcare team should carefully read the results of the CBC test. Keep in mind that many things, including cancer-free conditions, can lead to side effects. Ask your doctor to help you understand what your results mean.
Low white blood cell count. Other treatments for cancer, especially chemotherapy, can lower your white blood cells. Cancer of the blood and bone marrow can also reduce counts. These cancers include leukemia, lymphoma, and multiple myeloma.
The number of different white blood cells. Higher than normal lymphocytes or monocytes may indicate the possibility of certain types of cancer.
Some cancers and their treatment can cause neutropenia. Neutropenia is when a person has low levels of neutrophils. This increases the chance of getting a viral infection. In some cases, your doctor may reduce your dose of chemotherapy to reduce the risk of neutropenia. Your doctor may also recommend medications, such as growth factors for white blood cells, to increase your body's production of neutrophils, especially if you have a cold.
Low red blood cell count. Other cancers, especially chemotherapy and radiation, can lower your red blood cell count. This condition is known as anemia. Hemorrhage, either surgery or certain cancer, and cancer that directly involves the bone marrow can also cause or worsen anemia. People with very low blood cell counts may need a blood transfusion or medication to help increase it.
Low platelet count. Other cancer treatments, such as chemotherapy or radiation therapy, can cause platelet aggregation. Cancer involving the bone marrow can also lower the platelet count. An unusually low number of platelets is called thrombocytopenia. People with low platelets have a higher risk of severe bleeding or injury. If your platelet count falls too low, your doctor may recommend a platelet transfusion.
Questions to ask your health care team
Consider asking the following questions about your CBC test:
- Why am I having this test?
- How and where is this test done?
- Do I need to avoid eating and drinking before the test? If so, for how long?
- How will I get the results of my test?
- What are normal test results?
- What do my test results mean? Will someone explain them to me?
- If my results are within a normal range, what are the next steps?
- If my results are outside of a normal range, what are the next steps?
- How do these test results compare with my previous results?
- Will I need additional tests? If so, when?