A complete blood count (CBC), also called công thức máu, is one of the most common blood tests. Learning how to read a CBC means recognizing a handful of core values, knowing the usual reference ranges, and understanding what “high” or “low” is called for each line. This guide walks through the white blood cells, hemoglobin, hematocrit, platelets, MCV, and the differential in a calm, structured way.
This article is educational and does not replace clinical training or advice for a specific patient. All clinical decisions rest with the treating clinician.
What is a complete blood count?
A CBC is a panel that measures the main cellular components of blood: white blood cells (WBC), red blood cells and their indices, and platelets. Reading it well is a matter of pattern recognition. You compare each reported value against the reference interval printed on the report, then note the direction and size of any deviation.
One caution applies throughout: reference ranges vary by laboratory and by sex, so the numbers below are typical adult, lab-specific values. Always use the reference intervals printed by your own local laboratory, which are calibrated to its instruments and population. Definitions of the CBC components are summarized in the StatPearls complete blood count overview.
How to read a CBC step by step
A consistent order keeps interpretation systematic. Work through the panel line by line rather than jumping to a single value.
Step 1: Check the white blood cell count
Start with the total WBC, with a typical adult range of 4500 to 11000 cells/microL (StatPearls). A value above the range is called leukocytosis, and a value below the range is called leukopenia (StatPearls).
Step 2: Review hemoglobin and hematocrit
Hemoglobin is sex-specific, roughly 13 to 18 g/dL for men and 12 to 16 g/dL for women (StatPearls). Low hemoglobin is termed anemia (StatPearls). Hematocrit tracks alongside hemoglobin, with typical ranges of 40 to 54 percent for men and 36 to 48 percent for women (StatPearls).
Step 3: Read the platelet count
The adult platelet range is 150000 to 400000 per microL (StatPearls). A low count is thrombocytopenia, and a high count is thrombocytosis (StatPearls).
Step 4: Interpret the MCV
Mean corpuscular volume (MCV) reflects average red cell size, with an adult range of 80 to 100 fL (StatPearls). An MCV under 80 fL is microcytic, and an MCV over 100 fL is macrocytic (StatPearls). This size clue is often read together with the hemoglobin.
Step 5: Scan the differential
The differential breaks the WBC into cell types. Neutrophils are typically 40 to 60 percent, or about 1500 to 8000 cells/microL, and lymphocytes are typically 20 to 40 percent, or about 1000 to 4000 cells/microL (StatPearls). Reading both the percentage and the absolute count avoids being misled by proportion alone.
Normal values reference table
The table below collects the typical adult, lab-specific reference values discussed above. Values vary by laboratory and, where noted, by sex.
| Parameter | Typical adult range | Notes |
|---|---|---|
| WBC | 4500 to 11000 cells/microL | High = leukocytosis, low = leukopenia |
| Hemoglobin (men) | 13 to 18 g/dL | Low = anemia |
| Hemoglobin (women) | 12 to 16 g/dL | Low = anemia |
| Hematocrit (men) | 40 to 54 percent | Varies by sex |
| Hematocrit (women) | 36 to 48 percent | Varies by sex |
| Platelet count | 150000 to 400000 per microL | Low = thrombocytopenia, high = thrombocytosis |
| MCV | 80 to 100 fL | Under 80 = microcytic, over 100 = macrocytic |
| Neutrophils | 40 to 60 percent (1500 to 8000 cells/microL) | Part of the differential |
| Lymphocytes | 20 to 40 percent (1000 to 4000 cells/microL) | Part of the differential |
All values above are drawn from the StatPearls complete blood count reference and are lab-specific.
Common mistakes when reading a CBC
A few habits lead to misreads:
- Using a generic range instead of the local laboratory reference interval. Ranges vary by lab and instrument, so read the numbers printed on the actual report.
- Ignoring sex when reading hemoglobin and hematocrit. These parameters have different typical ranges for men and women (StatPearls).
- Reading only differential percentages and skipping the absolute counts. The neutrophil and lymphocyte lines carry both a percentage and an absolute count (StatPearls).
- Looking at one value in isolation rather than scanning the whole panel in order.
When to escalate
Interpretation of an out-of-range result belongs with a clinician who can place it in the context of the whole patient. Any value flagged outside the laboratory reference range, or any result that does not fit the clinical picture, should be reviewed by the treating clinician rather than acted on from a single number. This guide is educational and does not provide management or dosing advice.
Reading a CBC with Phở
Phở is a cited medical and research workspace. When you ask a clinical question, our grounded answer mode keeps sources next to the claims they support, so you can inspect where each statement comes from instead of trusting an unsourced summary. For a factual explainer like CBC interpretation, that means the reference values stay linked to their citation, and unsupported claims are labelled rather than invented. Phở supports understanding, not clinical decisions, which remain with the treating clinician.