The full blood count is the most commonly ordered blood test in Australian pathology. It measures the three main cell types in your blood: red blood cells, white blood cells, and platelets. Each has a distinct function, and changes in their numbers or characteristics can signal a range of conditions.
Red blood cells carry oxygen from your lungs to every tissue in the body. The FBC measures not just how many you have, but their size (MCV), haemoglobin content (MCH), and how much variation exists between them (RDW). These details help distinguish between different types of anaemia. Small, pale cells often point toward iron deficiency or thalassaemia trait. Large cells may suggest B12 or folate deficiency. Haemoglobin, the oxygen-carrying protein inside red cells, is one of the most clinically useful values on the report.
White blood cells are your immune system's front line. The FBC breaks them into subtypes: neutrophils (bacterial defence), lymphocytes (viral immunity), monocytes, eosinophils (allergy and parasites), and basophils. Shifts in these subsets give your practitioner clues about infection, inflammation, allergy, and in rarer cases, haematological conditions.
Platelets are the cells responsible for blood clotting. Too few can increase bleeding risk; too many may indicate inflammation or a bone marrow condition. The FBC reports platelet count alongside the mean platelet volume (MPV), which provides additional context.
Because the FBC captures so many parameters in a single test, it is used across nearly every branch of medicine. GPs use it for routine health checks, pre-operative assessments, fatigue investigations, infection workups, and monitoring the effects of medications on blood cell production. Results are always interpreted in context, and abnormalities on an FBC often prompt targeted follow-up testing.
To screen for anaemia, infection, immune disorders, and haematological conditions; to assess blood health as part of a routine health check; and to monitor the effects of medications or chronic illness on blood cell production.