Blood counts
Blood is made up of cells in a liquid called plasma. Blood cells are made in the bone marrow (the soft
center of the bones). Then they are released into the body to do their jobs. The body has three main
types of blood cells: red blood cells, white blood cells and platelets. This handout tells about normal
blood cell counts.
In patients with cancer involving the bone marrow, counting and studying blood cells can tell the medical team about a patient’s disease and how to treat it. If all three of the blood cell types are studied, the
test is called a complete blood count (CBC).
Blood counts are also monitored regularly in all cancer patients, since many cancer treatments affect the
bone marrow’s ability to make blood cells. Your child may have low blood counts following chemotherapy and radiation therapy. Many different factors help decide whether a patient with low blood counts
should be treated before the counts return to normal. Your child’s medical team will assess your child
and recommend treatment options.
Red blood cells
Red blood cells contain hemoglobin, a protein that carries oxygen to all parts of the body. We measure the hemoglobin level to check if the body will have enough oxygen for tissues to live and grow. A
normal hemoglobin level in healthy people is 12 g/dL. A lower hemoglobin level may cause a patient to
have pale skin color and to feel tired and dizzy. Some children become fussy, sleep more and play less.
When the hemoglobin level is very low, your child may need to receive a transfusion of red blood cells
from a blood donor.
White blood cells
White blood cells help the body fight infection. The normal white blood cell count in healthy people is
5,000 to 10,000/mm3. When the white blood cell count is low, it is easier to get an infection and harder
to get over it. The medical team will measure the white blood cell count often during cancer treatment to
see how well a patient can fight off infection. They will let you know if you need to take steps to avoid
infection.
Neutropenia
A neutrophil is a type of white blood cell that kills bacteria. It is one of the body’s main defenders
against infection. Neutropenia occurs when neutrophil counts in the blood are too low.
Neutropenia is a common side effect of cancer treatment. Chemotherapy (cancer fighting drugs) usually
affects the neutrophil count 7 to 14 days after a dose is received. The length of time it takes your child’s
blood counts to drop depends on the dose and type of drug used.
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Neutrophils are counted as part of the complete blood count (CBC). When checking a patient’s neutrophil count, the medical team relies on a count called the absolute neutrophil count (ANC). The ANC
gives an estimate of the body’s ability to fight infection, especially bacterial infections. For more information, see “GREAT information…Calculating the ANC.”
When the ANC is below 500/mm3, the risk of infection is high. During these times, it is important to
keep your child away from crowds, especially groups of children. In some cases, your medical team may
decide that your child should wear a face mask (particulate mask) to lower his or her risk of infection.
If fever develops while your child is neutropenic (having a low neutrophil count), you need to call the
doctor right away. Tests will be done to find the cause of the fever. Your child may be admitted to the
hospital for antibiotic treatment and closer monitoring.
Platelets
Platelets are blood cells that help stop bleeding by making the blood clot. A normal platelet count in
healthy people is 150,000 to 400,000/mm3. Bruising and bleeding often happen when platelet counts are
low. A platelet transfusion may be needed when the platelet count is very low.
Some warning signs of a low platelet count include:
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Tiny red spots under the skin (petechiae),
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Blood oozing from the mouth and gums,
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Nosebleeds,
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Urine that is pink or red, and
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Stools that are red or black.
Monitoring your child’s blood counts will be an important part of the treatment plan. The medical staff
will review these results with you often. You may find it helpful to record the results on a blood counts
log. A blank copy of the log is located in the GREAT Book.
Adapted with permission from St. Jude Children’s Research Hospital. Revised 6/04
UC Davis Cancer Center 12/06
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