Lab test · Blood count
Complete blood count (CBC)
A complete blood count measures red cells, white cells and platelets. What each part of a CBC shows and why it is one of the most commonly ordered blood tests.
Written by LON6EVITY Editorial Team · Last updated
What it measures
MedlinePlus describes a CBC as a test that measures several parts of the blood: red blood cells (including hemoglobin and hematocrit), white blood cells and platelets, and often red cell indices such as cell size.
Why it is ordered
A CBC is part of many routine check-ups and is used to look for anaemia, infection, inflammation, bleeding problems and some blood disorders, or to monitor treatment.
Reading results
Results are compared with the laboratory's reference ranges. Small deviations are common and often not significant; patterns across several values and repeat tests matter more than one number.
Factors that can affect the result
- Hydration
- Recent infection
- Altitude
- Pregnancy
- Medicines
Questions people commonly ask
- Do I need to fast for a CBC?
- Usually not, unless other tests are drawn at the same time.
- What does red cell size tell you?
- Small cells often point toward iron deficiency; large cells can suggest B12 or folate deficiency, among other causes.
Related biomarkers
Keep your health results in one place
What does this mean for your own health data? Log your results, follow trends over time and bring an organised summary to your next doctor's appointment.
Sources
- Complete Blood Count (CBC). MedlinePlus, U.S. National Library of Medicine.