What does a CBC check for during treatment?

A complete blood count, often called a CBC, is a blood test. It measures red blood cells, white blood cells, and platelets. It also measures hemoglobin and hematocrit. The CBC is one of the most common lab tests in cancer care. It can help diagnose some cancers, especially leukemias. It is also used to monitor your health during and after treatment.

During chemotherapy, white blood cell counts can drop at certain times. So your care team checks your CBC often. They watch for a drop in white cells called neutropenia. They also watch for changes in your red blood cells and platelets. This is one reason you may have blood drawn at almost every treatment visit.

Normal results vary from person to person, and even from day to day. That is why results are reported as a range, with lower and upper limits. There is no one fixed number everyone should match. If a result looks different from what you expected, ask your care team what it means for you. One number on its own does not tell the whole story.