CBC Blood Test Report Explained: Haemoglobin, WBC and Platelets
How to read a complete blood count report: haemoglobin, MCV, white cells and their types, platelets, normal ranges, and what common high or low flags mean.
Key takeaways
- A CBC measures three cell lines: red cells (oxygen), white cells (infection and allergy) and platelets (clotting).
- Most single flags slightly outside the range are not serious. Patterns across several values, and change over time, matter more.
- Low haemoglobin with low MCV usually means iron deficiency or thalassaemia trait, both very common in India.
- High eosinophils often point to allergy or intestinal worms; low platelets during a fever raise the question of dengue.
The complete blood count, or CBC, is the most ordered blood test in the world, and the report looks like a wall of abbreviations with a few values marked H or L. Most flags turn out to be minor; a few matter a great deal. This guide explains each line in plain language and the patterns doctors look for.
Quick answer
A CBC counts red cells, white cells and platelets. Red cells carry oxygen (haemoglobin, MCV and related values), white cells fight infection and allergy, and platelets help clotting. A single value slightly outside the range is usually not serious. Patterns matter: low haemoglobin with low MCV suggests iron deficiency or thalassaemia trait; low platelets with fever raises the question of dengue.
The red cell values
| Value | What it measures | Typical adult range |
|---|---|---|
| Haemoglobin (Hb) | Oxygen-carrying protein | Men about 13 to 17 g/dL; women about 12 to 15 g/dL |
| RBC count | Number of red cells | Men about 4.5 to 5.5; women about 3.8 to 4.8 million per microlitre |
| PCV or haematocrit (HCT) | Share of blood made of red cells | Men about 40 to 50 percent; women about 36 to 46 percent |
| MCV | Average red cell size | About 83 to 101 fL |
| MCH, MCHC | Haemoglobin per cell | Lab specific |
| RDW | Variation in red cell size | About 11.6 to 14 percent |
Low haemoglobin means anaemia. MCV tells you its likely type: small cells (low MCV) suggest iron deficiency or thalassaemia trait; large cells (high MCV) suggest vitamin B12 or folate deficiency, alcohol, thyroid disease or some medicines. See the iron deficiency guide and the B12 guide.
Thalassaemia trait: worth knowing in India
Low MCV with a normal or high red cell count and a normal ferritin often means thalassaemia trait, which is common in India. It is not a disease and needs no iron, but if both partners carry it, a child can have thalassaemia major. An HbA2 test confirms it, and it is worth knowing before pregnancy.
The white cell values
| Value | Typical range | Common reasons it rises |
|---|---|---|
| Total WBC (TLC) | About 4,000 to 11,000 per microlitre | Infection, inflammation, steroids, smoking, stress |
| Neutrophils | About 40 to 75 percent | Bacterial infection |
| Lymphocytes | About 20 to 40 percent | Viral infection, recovery from illness |
| Eosinophils | About 1 to 6 percent | Allergy, asthma, eczema, intestinal worms |
| Monocytes | About 2 to 10 percent | Recovery from infection, chronic inflammation |
| Basophils | Below about 1 percent | Rarely significant on its own |
A low white count is common after viral fevers and usually recovers. A very high count, a very low count, or a report that mentions “atypical cells”, “blasts” or recommends a peripheral smear review needs prompt medical attention.
Platelets
Platelets are tiny cells that start clotting. A typical range is about 150,000 to 410,000 per microlitre, often written as 1.5 to 4.1 lakh. Low platelets during a fever are common in dengue and other viral infections and usually recover; the dengue guide explains what to watch. Falsely low counts sometimes happen when platelets clump in the sample tube, so an unexpected low result without symptoms is often repeated. High platelets often follow infection, inflammation or iron deficiency.
How to read the whole report
Look at the three lines together rather than one flag at a time. Compare with an earlier CBC if you have one, since a stable mild abnormality matters less than a new or changing one. Remember that recent illness, exercise, pregnancy and medicines shift values. Take the report to the doctor who ordered it with your questions, and see the reports hub for other common tests.
When to see a doctor promptly
Haemoglobin below about 8 g/dL, platelets below about 50,000, white cells below about 2,000 or above about 20,000, any mention of abnormal or immature cells, or unexplained bruising, bleeding gums, frequent infections, weight loss or night sweats. Bleeding with low platelets, or fever with very low white cells, needs same-day care.
Frequently asked questions
What is a normal CBC?
Typical adult ranges are haemoglobin about 13 to 17 g/dL in men and 12 to 15 g/dL in women, white cells about 4,000 to 11,000 per microlitre, and platelets about 150,000 to 410,000 per microlitre. Each lab prints its own reference range, which is the one to use.
What does low MCV mean?
MCV is the average size of red cells. Low MCV means small red cells, most often caused by iron deficiency or thalassaemia trait. A ferritin test helps tell them apart: it is low in iron deficiency and usually normal in thalassaemia trait.
What does a high eosinophil count mean?
Eosinophils rise with allergies, asthma, eczema and parasitic infections such as intestinal worms, which are common in India. A mild rise with allergy symptoms is usually explained by the allergy. A persistently high or very high count needs a doctor to look for the cause.
Is a platelet count of 1 lakh dangerous?
A platelet count of 100,000 per microlitre is below normal but is not dangerous on its own and does not cause bleeding. During a fever, it raises the possibility of dengue or another viral infection and needs repeat testing. The <a href="/blog/dengue-vs-viral-fever/">dengue guide</a> explains the warning signs that matter more than the number.
Why is my WBC count high?
The commonest cause is a bacterial infection, which raises neutrophils. Steroid medicines, smoking, stress, recent exercise and pregnancy also raise it. A very high count, or abnormal cells mentioned on the report, needs a prompt review.
Sources
Dr. Garima Panse is a medical doctor who writes plain-language guides for Indian readers on skin health, heart health, brain and nerves, medical imaging and everyday medicine. Every guide lists its sources, shows the date it was last reviewed, and says when to see a doctor in person.
This guide is for general education and reflects the evidence available on the last reviewed date. It is not a diagnosis, a prescription or a substitute for seeing a doctor who can examine you. If you have symptoms that worry you, or the guide tells you to see someone, please do. Full disclaimer.