A CBC is collected from a blood sample and is often ordered when a doctor wants to check several aspects of your blood health at once. The complete blood count includes measurements for red blood cells, white blood cells, haemoglobin and platelets. It can be part of a routine check or help your clinician investigate why you have been feeling tired, weak or unwell.

You may see several rows on the report because a CBC measures different parts of the blood separately. Haemoglobin is one of the values your doctor may review when looking for anaemia, while the white cell count and platelet count help answer different questions. A flagged value can have several explanations. Your doctor will look at how the values fit together and may compare the result with an earlier CBC before deciding whether another test is needed.