Platelet Count Blood Test

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KEY POINTS

• A platelet count blood test checks the number of platelets in the blood. It is usually part of another blood test called a complete blood count or CBC.
• 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 a vein in your child’s arm with a needle. The blood is collected in tubes and sent to a lab.
• Talk to your child’s healthcare provider about what the test results mean and ask any questions you have.

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What is a platelet count blood test?

A platelet count blood test checks the number of platelets in the blood. It is usually part of another blood test called a complete blood count or CBC. It is a common and useful blood test.

Platelets are also called thrombocytes. Platelets are not actually blood cells. They are small pieces of large blood-forming cells. They are made in the bone marrow and are needed for normal blood clotting to stop bleeding.

Why is this test done?

A platelet count may be done as part of your child’s overall health checkup. It may also be done to check for:

• Problems with blood clotting
• Problems with bleeding

This test may also be done to see how well treatment for a disease or condition is working.

How do I prepare my child for this test?

Usually no preparation is needed for this test.

Talk to your healthcare provider if you have any questions about the test.

How is the test done?

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 a vein in your child’s arm with a needle. The blood is collected in tubes and sent to a lab.

Ask your child’s healthcare provider how and when you will get your child’s test results.

What do the test results mean?

Some of the reasons your child’s platelet count may be higher than normal are:

• Your child is dehydrated.
• Your child has certain infections.
• Your child has had a blood loss such as from surgery.
• Your child has a certain type of cancer such as leukemia or lymphoma.
• Your child has a problem getting enough iron and vitamin B12 from food.
• Your child has a certain type of anemia, which is a problem with the red blood cells.
• Your child has had a serious allergic reaction.
• Your child has an autoimmune disease (a disease that causes your body to mistakenly attack your own tissue) such as rheumatoid arthritis or Crohn’s disease.
• Your child’s spleen has been removed in surgery.
• Your child has an inherited disease, which means that it is passed from parents to children through their genes. Genes are inside each cell of your body. They contain the information that tells your body how to develop and work.

A high platelet count is also called thrombocytosis.

Some of the reasons your child’s platelet count may be lower than normal are:

• Your child’s bone marrow does not make enough platelets.
• Your child’s body uses up the platelets faster than normal.
• Your child has a certain type of cancer such as leukemia or lymphoma.
• Your child has a problem getting enough iron and vitamin B12 from food.
• Your child is taking certain medicines such as sulfa drugs, quinine, heparin, or cancer drugs.
• Your child has a blood infection or another serious illness.
• Your child has an autoimmune disease.
• Your child has an inherited disease, which means that it is passed from parents to children through their genes. Genes are inside each cell of your body. They contain the information that tells your body how to develop and work.

A low platelet count is also called thrombocytopenia.

What if my child’s test result is not normal?

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:

• If your child needs more tests
• What kind of treatment your child might need
• What lifestyle, diet, or other changes your child might need to make