The complete blood count is the test most people see first, and the one most often misread. It reports a dozen or more values with no explanation, and a single letter H or L next to a number carries very different weight depending on which line it is on.
This guide walks through every marker on a standard CBC with differential: what it measures, what a high value usually means, what a low value usually means, and when the number is worth a conversation with your provider. It is educational, not medical advice.
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A CBC is ordered at almost every annual physical, before surgery, during pregnancy, and any time symptoms suggest infection, anemia, or a bleeding problem. It is also used to monitor people on medications that can affect blood counts.
Because it is run so often, the CBC is usually the marker set with the most history attached to it. Comparing today's values to your own past results tells you far more than comparing them to a population range.
Ranges vary by lab, age, and sex. Always read the range printed on your own report.
| Marker | Typical range |
|---|---|
| Hemoglobin | Men 13.5-17.5 g/dL; women 12.0-15.5 g/dL |
| Hematocrit | Men 41-53%; women 36-46% |
| Red blood cell count (RBC) | Men 4.5-5.9 M/uL; women 4.1-5.1 M/uL |
| MCV (mean corpuscular volume) | 80-100 fL |
| MCH and MCHC | MCH 27-33 pg; MCHC 32-36 g/dL |
| RDW (red cell distribution width) | 11.5-14.5% |
| White blood cell count (WBC) | 4,500-11,000 /uL |
| Neutrophils | 40-70% of WBC |
| Lymphocytes | 20-40% of WBC |
| Monocytes, eosinophils, basophils | Monocytes 2-8%; eosinophils 1-4%; basophils 0-1% |
| Platelets | 150,000-450,000 /uL |
The oxygen-carrying protein inside red blood cells. It is the single best number for spotting anemia.
The share of your blood volume made up of red cells. It tracks closely with hemoglobin.
The total number of red blood cells per volume of blood.
The average size of your red blood cells. It is the fastest clue to which type of anemia you have.
How much hemoglobin the average red cell carries, in absolute terms and by concentration.
How much variation there is in red cell size. A high RDW means the cells are unevenly sized.
Your total immune cell count, the frontline response to infection and inflammation.
The white cells that respond first to bacterial infection and tissue injury.
The white cells that handle viral defense and long-term immune memory.
Smaller white cell subsets involved in cleanup, allergic response, and parasite defense.
Cell fragments that let blood clot after injury.
Read the CBC as three related stories rather than a list. The red cell line, hemoglobin, hematocrit, RBC, MCV, and RDW, answers whether you are anemic and what kind. The white cell line, WBC plus the differential, answers whether your immune system is responding to something. Platelets stand mostly on their own.
A single flagged value inside an otherwise clean CBC is usually rechecked rather than treated. A pattern, such as low hemoglobin with a low MCV and a high RDW, is much more informative than any one flag, and it is exactly the kind of grouping Nodava does automatically when you upload a report.
View a fully explained sample report first, or upload your own and get the same breakdown for every marker on it.