Short answer: A complete blood count (CBC, or full blood count in the UK) counts and measures the cells in your blood: red cells, which carry oxygen; white cells, which fight infection; and platelets, which help blood clot. It is the most common blood test, often part of a routine check, and the report has 10 to 20 lines, each with its own reference range.
At a glance
| Red cells | Haemoglobin, haematocrit, RBC count, MCV, MCH, RDW |
|---|---|
| White cells | Total count and differential: neutrophils, lymphocytes, monocytes, eosinophils, basophils |
| Platelets | Count and MPV |
| Units | g/dL or g/L for haemoglobin; cells per µL or ×10⁹/L for counts |
| LOINC | 58410-2 (CBC panel) |
| Keep | Every line with its unit and range; the same line is compared over time |
What the test measures
The CBC is done on a small tube of blood with an anticoagulant (the purple-top tube in most labs), analysed by an automated counter in minutes. The report groups the results in three families:
- Red cells: the number of erythrocytes, haemoglobin (the protein that carries oxygen), haematocrit (the share of the blood volume made of red cells) and the red cell indices: MCV (average size), MCH and MCHC (haemoglobin per cell) and RDW (how much the cells vary in size).
- White cells: the total white cell count (WBC) and, in a "differential", the share or number of each type: neutrophils, lymphocytes, monocytes, eosinophils, basophils.
- Platelets: their number, sometimes with the mean platelet volume (MPV).
When it is ordered
Common reasons, which your doctor adapts to you:
- as part of a routine check-up or before surgery;
- when a doctor looks for a cause of tiredness, bruising, fever or infection;
- to follow a known condition or a treatment that affects the blood.
How the result is written on the report
| Result on the report | LOINC code | Usual unit | Also seen as |
|---|---|---|---|
| Haemoglobin | 718-7 | g/dL | g/L (×10), mmol/L |
| Haematocrit | 4544-3 | % | L/L (÷100) |
| Red blood cells | 789-8 | 10*6/µL | 10^12/L (same number) |
| MCV | 787-2 | fL | — |
| MCH | 785-6 | pg | — |
| MCHC | 786-4 | g/dL | g/L |
| RDW | 788-0 | % | — |
| White blood cells | 6690-2 | 10*3/µL | 10^9/L (same number) |
| Neutrophils (%) | 770-8 | % | — |
| Lymphocytes (count) | 731-0 | 10*3/µL | 10^9/L |
| Platelets | 777-3 | 10*3/µL | 10^9/L (same number) |
Counts are written as cells per microlitre (10*3/µL in UCUM, often shown as ×10³/µL) in the US and much of Europe, or per litre (10^9/L) in the UK and other countries: 6.5 ×10³/µL and 6.5 ×10⁹/L are the same number. Haemoglobin appears as g/dL (14.0) or g/L (140), and some countries use mmol/L.
Reading your report
Reference ranges for haemoglobin and haematocrit differ between men and women, and for children by age; the laboratory prints the range that applies to you. One value slightly outside the range is common and often has no meaning on its own; doctors look at the pattern (for example, low haemoglobin together with a low MCV) and at the change since your last count. Keep the differential: a total white count can be normal while one type of white cell is not.
Keeping the results in your record
Scan or photograph the report in Anpheros Daily: each value is read with its unit and the laboratory's reference range, you check it, and it is stored with its LOINC code as an HL7 FHIR Observation, a format used by many hospitals and national health systems. Results from different laboratories line up on one chart over time, and the lab unit converter helps when two reports use different units. Our guide on how to read lab results explains reference ranges and flags in general; the lab results guide for a new doctor shows how to share them.
What this page does not do
It explains what the test is and how the result is written. It does not interpret your result, diagnose or recommend treatment: the meaning of a value depends on your history, your other results and how the sample was taken, and that is your doctor's job.
Related pages
Sources
Frequently asked questions
Is a CBC the same as a full blood count?
Yes. CBC is the US name, FBC the UK name; the panel is the same, although labs may include slightly different lines.
Do I need to fast for a CBC?
Usually not. A CBC is not affected by a meal, but it is often taken with other tests that do need fasting, so follow the instructions you were given.
Why do my white cells show 10^9/L on one report and ×10³/µL on another?
They are two ways of writing the same quantity: one per litre, one per microlitre. The number does not change.
Can I compare CBC results from two different labs?
Yes, if you keep the units and the reference range of each report. Analysers differ slightly, so look at the trend over several results rather than one small difference.
Try it in Anpheros Daily
Photograph your lab report and Anpheros Daily lines up each value with its reference range, so you can compare reports from different laboratories.
How it works in the app →
Anpheros builds a medical record that the patient controls and can share with any clinic, on an HL7 FHIR R4 platform, based in the EU. These guides help you understand and organise your health; they do not replace your doctor.
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