A complete blood count (CBC) checks the blood cells in the blood. It measures the numbers of different types of blood cells, their sizes, and their appearance. It is a very common and useful blood test.
In general, the test measures 3 main components of blood:
The CBC test may be done to check your child’s overall health. It may also be done to check for:
Usually no preparation is needed for this test.
Talk to your healthcare provider if you have any questions about the test.
Having this test will take just a few minutes. If your child is a newborn, your child's healthcare provider makes a tiny cut in the baby's heel to get a small amount of blood to test. For older children, a small amount of blood is taken from the fingertip or from a vein in your child’s arm with a needle. The blood is collected in tubes and sent to a lab.
Ask your healthcare provider when and how you will get the result of the test.
Red blood cell count
Some of the reasons your child’s red blood cell count may be higher than normal are:
A red blood cell count or hemoglobin level lower than normal is called anemia. The size of the red blood cells can help your child’s healthcare provider know what might be causing the anemia.
White blood cell count
Some of the reasons your child’s white blood cell count may be higher than normal are:
Your child’s white blood cell count may be lower than normal if your child has a viral infection, including the common cold, or is getting cancer treatment (chemotherapy).
Your child’s platelet count may be higher than normal if your child has an autoimmune disease (a disease that causes your child’s body to attack its own tissue), such as juvenile arthritis or lupus. The platelet count can also go up with viral infections, but it will go back to normal as your child recovers.
Some of the reasons your child’s platelet count may be lower than normal are:
Test results are only one part of a larger picture that takes into account your child’s medical history and current health. Sometimes a test needs to be repeated to check the first result. Talk to your child’s healthcare provider about your child’s result and ask questions, such as: