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A complete blood count (CBC) measures your red blood cells and hemoglobin, white blood cells and platelets. Values slightly outside the lab's reference range are often not serious, but persistent or marked abnormalities, or more than one abnormal cell line, should be reviewed by a doctor or hematologist.
The complete blood count (CBC), also called a hemogram, is the most common blood test. It gives a snapshot of the three main types of blood cells. Each laboratory prints its own reference range next to your result, and that range is the one to use. The figures below are typical adult values and are only a guide.
1. Hemoglobin and red blood cells
| Test | What it measures | Typical adult range |
|---|---|---|
| Hemoglobin (Hb) | Oxygen-carrying protein in red cells | Men about 13–17 g/dL; women about 12–15 g/dL |
| RBC count | Number of red cells | About 4.5–5.5 million/µL (men), 3.8–4.8 million/µL (women) |
| MCV | Average size of red cells | About 80–100 fL |
| MCH | Average hemoglobin per red cell | About 27–32 pg |
| RDW | Variation in red cell size | About 11.5–14.5% |
Low hemoglobin means anemia. The MCV helps find the cause: small cells (low MCV) suggest iron deficiency or thalassemia trait; large cells (high MCV) suggest vitamin B12 or folate deficiency, liver disease, some medicines or bone marrow problems. A low MCV with a high RBC count and near-normal hemoglobin is a typical clue to thalassemia trait, which needs a hemoglobin HPLC test to confirm.
2. White blood cells (WBC)
The total WBC count is typically about 4,000–11,000 per µL. The differential count splits it into neutrophils, lymphocytes, monocytes, eosinophils and basophils.
- High WBC is most often due to infection or inflammation. Very high counts, or immature cells ("blasts") on the smear, need urgent evaluation for leukemia.
- Low WBC or low neutrophils can follow viral infections or medicines, but persistent low counts need review. A fever with very low neutrophils, especially during chemotherapy, is an emergency.
- High eosinophils are commonly due to allergy or worm infection; persistent, very high levels need a hematologist's opinion.
3. Platelets
A typical platelet count is about 1.5–4.5 lakh (150,000–450,000) per µL. Low platelets (thrombocytopenia) are common in dengue and other viral fevers and usually recover. Persistently low platelets may be due to ITP, medicines, an enlarged spleen or a bone marrow disorder. Sometimes a machine shows a falsely low count because platelets clump in the tube; a smear or repeat test in a different tube can confirm this. Persistently high platelets also deserve evaluation.
When should a CBC report worry you?
- Two or three cell lines are abnormal at the same time (for example low hemoglobin and low platelets).
- Blasts or abnormal cells are reported on the peripheral smear.
- Hemoglobin is below about 7–8 g/dL, or falling quickly.
- Platelets are below about 20,000–30,000/µL, or there is any bleeding.
- An abnormality persists on repeat testing over weeks.
In these situations, see a hematologist rather than treating the numbers on your own. Never start iron, steroids or other medicines based only on a report without a diagnosis.
This guide is general health information and is not a substitute for a consultation. Reference ranges and recommendations can differ between laboratories and individuals.