What is a complete blood count (CBC)?
Updated October 18, 2026
A complete blood count, or CBC, is one of the most common blood tests. It counts the cells in your blood. It is often part of a regular checkup.
The main parts
| Test | What it shows | Common adult range* |
|---|---|---|
| White blood cells (WBC) | The cells that fight infection. | About 4,500 to 11,000 per microliter |
| Red blood cells (RBC) | The cells that carry oxygen. | About 4.2 to 5.9 million per microliter |
| Hemoglobin (HGB) | The protein in red cells that holds oxygen. | About 12 to 15.5 g/dL for women, 13.5 to 17.5 g/dL for men |
| Hematocrit (HCT) | The share of your blood made of red cells. | About 36 to 46% for women, 41 to 50% for men |
| Platelets (PLT) | Small cells that help blood clot. | About 150,000 to 450,000 per microliter |
*Common ranges only. Labs differ, so use the range printed on your report.
What a result can mean
Low hemoglobin can be a sign of anemia, which has many causes, such as low iron, blood loss, or other conditions. A high white cell count often points to the body fighting an infection or inflammation. Platelets that are very low or very high are worth a call to your doctor. These are only general patterns. Only your doctor can tell you what a result means for you.
Questions to ask
- Is this result new, or has it been like this before?
- Do we need to repeat the test, or run another one?
- Could a medicine or something in my diet explain it?
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