A complete blood count (CBC) is a blood test that measures many different parts and features of your blood. It is a common medical test that is often part of a routine checkup and can help detect a variety of disorders including infections, anemia, diseases of the immune system, and blood cancers. A CBC measures and counts your blood cells, including:

• Red blood cells, which carry oxygen from your lungs to the rest of your body
• White blood cells, which fight infections and other diseases
• Platelets, which stop bleeding by helping your blood to clot
• Hemoglobin, a protein in red blood cells that carries oxygen from your lungs to the rest of your body
• Hematocrit, a measurement of how much of your blood is made up of red blood cells
• Mean corpuscular volume (MCV), a measure of the average size of your red blood cells

A CBC can show unusual increases or decreases in cell counts, which might point to a medical condition that calls for more testing. However, a CBC usually doesnt give all the answers about a diagnosis, and results outside the expected range may or may not need follow-up. A health care provider might need to look at the results of other tests as well as the results of a CBC.