Complete blood count (CBC)

What this test is

A complete blood count, or CBC, checks three things. These are red cells, white cells, and platelets. It can help explain tiredness, odd bruising, or bleeding. It can also help explain signs of infection. It is used to watch some medical conditions. It also watches some medications. A CBC is a good test when you have a symptom like this. It also helps when there is a reason to monitor your blood. It is not usually needed every year if you feel well. This is true if you have no symptoms. It is also true if you take no medication that affects blood counts. Ordering it without a reason can find small, harmless changes. These changes can lead to more testing and worry, without helping you.