Blood tests


If you have been diagnosed with breast cancer or if your doctor thinks you might have it, you may have a variety of blood tests. Throughout and after breast cancer treatment, you will also need blood tests.

The most common types of blood tests for people with breast cancer are a complete blood count test, which checks the amount of red and white blood cells and platelets in the blood, blood chemistry tests and blood tumor marker tests, which may help detect whether cancer is present in other areas of the body.

Complete blood count test (CBC)

This test may be given before, during and after treatment. A CBC looks at how many red and white blood cells you have. It may also suggest the presence of cancer in your bone marrow, where blood cells are formed. A low number of white blood cells, which help build up your body’s immunity, may indicate you have an infection or are at risk of developing one.

Red blood cells, which contain an iron-rich protein called hemoglobin, are responsible for carrying oxygen throughout your body. They also help provide energy. If you have a low red blood cell count, you may be anemic. Anemia is often a side effect of certain treatments, especially chemotherapy.

A CBC will also test for platelets, cells in the blood that help you form blood clots so that any bleeding can be stopped.

Your blood cell count will probably be tested before each chemotherapy treatment. If you do not have enough red or white blood cells, you can take medicines to increase the levels of these cells.

Blood chemistry test

Blood chemistry tests measure the levels of certain substances in your blood. They can provide information about the health of important organs, such as the liver, kidneys and bones. Testing these substances can help your doctor investigate whether the cancer may have traveled from the breast to other areas of your body.

Blood tumor marker test

Some tumors create proteins or circulating tumor cells that break away from the tumor and move throughout your body. During a blood marker test, also called a blood tumor marker test, doctors will look for these proteins or cells in your blood.

These tests may be done at different times before, during and after treatment. The results of these tests are sometimes used to guide treatment.

Blood tumor marker test results can sometimes be unreliable, and they are expensive. But they may help your doctor know whether you need more tests to monitor your overall health.


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Reviewed and updated: August 31, 2015

Reviewed by: Carla S. Fisher, MD , Lauren Ende Schwartz, MD


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