Blood Test: Complete Blood Count (for Parents) - Nemours KidsHealth

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Blood Test: Complete Blood Count en español: Análisis de sangre: Hemograma completo Medically reviewed by: Larissa Hirsch, MDThis link opens in a new tab Learn About Primary Care Pediatrics at Nemours Children's HealthThis link opens in a new tab

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What Is a Blood Test?

By taking and testing a small sample of a person’s blood, doctors can check for many kinds of diseases and conditions. Blood tests help doctors check how the body’s organs are working and see if medical treatments are helpful.

To help your child get ready for a blood test, find out if they need to fast (not eat or drink) or should stop taking medicines before the test. Explain what to expect during the test. If your child is anxious about it, work together on ways to stay calm.

What Is a Complete Blood Count?

A complete blood count (CBC) test is a blood test that helps doctors check the levels of different types of cells in the blood. A CBC measures:

• red blood cells, which deliver oxygen to the different parts of the body
• white blood cells, which help fight infections
• platelets, which help blood clot to stop bleeding

Why Are CBCs Done?

Doctors may order a CBC as part of a routine checkup to screen for problems or because a child isn't feeling well. The levels of red blood cells, white blood cells, and platelets can help doctors find possible problems like anemia, infections, inflammation, and other conditions.

Let the doctor know if your child smokes or has had a blood transfusion. These can affect the CBC.

What if I Have Questions?

If you have questions about the CBC or what the test results mean, talk to your doctor.

Medically reviewed by: Larissa Hirsch, MDThis link opens in a new tab Date reviewed: March 2023

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