Full Blood Count (FBC) Explained: What Each Marker Means

The full blood count (FBC), also known as a complete blood count (CBC), is one of the most frequently ordered blood tests in Australia. It provides a broad overview of your blood health, screening for conditions ranging from anaemia and infection to more serious blood disorders.

What Is a Full Blood Count?

An FBC measures the levels and characteristics of three main types of cells in your blood: red blood cells (which carry oxygen), white blood cells (which fight infection), and platelets (which help your blood clot). In Australia, FBC testing is covered by Medicare when ordered by a registered medical practitioner.

Red Blood Cell Markers

Haemoglobin (Hb)is the oxygen-carrying protein in red blood cells. Normal ranges are typically 130–170 g/L for men and 120–150 g/L for women. Low haemoglobin indicates anaemia, while elevated levels may suggest dehydration or polycythaemia.

Mean Cell Volume (MCV)measures the average size of your red blood cells (normal: 80–100 fL). Small cells (low MCV) often point to iron deficiency, while large cells (high MCV) suggest B12 or folate deficiency.

Red Cell Distribution Width (RDW) measures variation in red blood cell size. Recent research has linked elevated RDW to increased cardiovascular risk and all-cause mortality, making it a marker worth tracking.

White Blood Cell Markers

The total white blood cell count (normal: 4.0–11.0 × 10⁹/L) screens for infection, inflammation, and immune disorders. The differential breaks this into subtypes: neutrophils (bacterial infection), lymphocytes (viral immunity), monocytes (chronic inflammation), eosinophils (allergies and parasites), and basophils (inflammatory responses).

The neutrophil-to-lymphocyte ratio has been studied as a predictor of cardiovascular events and systemic inflammation.

Platelet Markers

Platelets (normal: 150–400 × 10⁹/L) are essential for blood clotting. Low counts increase bleeding risk; high counts may indicate inflammation or a bone marrow disorder. Mean Platelet Volume (MPV) measures average platelet size — larger platelets are generally younger and more active.

Tracking Your FBC Over Time

A haemoglobin level of 125 g/L in a woman might be within normal range, but if it was 140 g/L a year ago, the downward trend warrants investigation. Regular annual blood testing creates a personal baseline, making it far easier to spot clinically significant changes early.

References

1. Bain BJ. Blood Cells: A Practical Guide, 5th Edition. Oxford: Wiley-Blackwell, 2015.
2. Royal College of Pathologists of Australasia (RCPA). RCPA Manual: Full Blood Count.
3. Salvagno GL, et al. Red blood cell distribution width: A simple parameter with multiple clinical applications. Crit Rev Clin Lab Sci. 2015;52(2):86–105.
4. Forget P, et al. What is the normal value of the neutrophil-to-lymphocyte ratio? BMC Res Notes. 2017;10(1):12.