In brief
One of the most common blood tests. It counts and measures red blood cells, white blood cells and platelets.
What it measures
Haemoglobin, the iron-containing protein that carries oxygen in red cells; the number of red blood cells and their average size (MCV); the number of white blood cells and their five types; and platelets, which help blood clot.
Why it is done
To help screen for, diagnose and monitor many conditions, including anaemia, blood clotting problems, infections, blood cancers and immune system disorders.
Reading the results
- Low haemoglobin means anaemia.
- A low MCV means red cells are smaller than normal, and a high MCV means they are larger than normal.
- Both increases and decreases in white cells can be signs of health problems. Infection or inflammation raises white cell production.
- Too few platelets can lead to bruising or bleeding, and too many can lead to blood clots.
A result flagged as high or low does not necessarily mean that anything is wrong.
Before the test
None.
What can affect the result
- Infection or inflammation
- Pregnancy
- Altitude and smoking
- Some medicines
Related topics
Connections
Full blood count (FBC) measures
A full blood count counts and measures red blood cells, white blood cells and platelets.
A full blood count measures haemoglobin, and low haemoglobin means anaemia.
Sources: Pathology Tests Explained, Full blood count; healthdirect Australia, Anaemia
Sources
Test information summarised from the sources listed on this page, read on 19 October 2026. General education only, not medical advice. Spotted a mistake? Please tell us through the HuBu-Intel contact page.