How to read a CBC report, line by line

A Complete Blood Count — CBC — is the most common blood test ordered in India. It measures the cells that make up your blood: red cells, white cells, and platelets. If you've ever been handed a CBC report and felt lost in a wall of abbreviations, this guide is for you.

What a CBC actually measures

Your blood has three main cell types:

Cell type	What it does
Red blood cells (RBC)	Carry oxygen from lungs to tissues
White blood cells (WBC)	Fight infection and foreign invaders
Platelets	Form clots to stop bleeding

A CBC counts these cells, measures their size and health, and checks a few proteins inside them (notably haemoglobin). It's the test your doctor reaches for first when you're unwell, tired, or before surgery.

The report, row by row

Haemoglobin (Hb)

The oxygen-carrying protein inside red blood cells. This is usually the single most important number on the CBC.

Adult men: 13.5–17.5 g/dL
Adult women: 12.0–15.5 g/dL
Children (6–12): 11.0–14.0 g/dL

Low haemoglobin = anaemia. In India, the most common cause is iron deficiency — especially in women of reproductive age. See the hemoglobin reference page for low/high meanings and FAQs.

Haematocrit (HCT or PCV)

The percentage of your blood that is red blood cells. Moves in the same direction as haemoglobin — so if Hb is low, HCT usually is too. Dehydration can falsely raise it.

RBC count

The absolute number of red blood cells per microlitre. Less informative than haemoglobin on its own but useful alongside MCV and MCH (below) to classify the type of anaemia.

MCV, MCH, MCHC — the "red-cell indices"

These three numbers tell your doctor what kind of anaemia you have, if any.

MCV (Mean Corpuscular Volume) — the average size of a red blood cell.
- Low MCV → microcytic → usually iron deficiency or thalassaemia.
- High MCV → macrocytic → usually B12 or folate deficiency.
MCH (Mean Corpuscular Haemoglobin) — how much haemoglobin each cell carries.
MCHC — haemoglobin concentration within each cell.

You don't need to memorise the cutoffs. What matters is the pattern: if your haemoglobin is low and your MCV is also low, your doctor will likely check iron studies next.

RDW (Red cell Distribution Width)

A measure of how varied your red cells are in size. A high RDW often shows up before haemoglobin drops, making it an early clue for iron or B12 deficiency.

WBC count (Total Leukocyte Count, TLC)

Normal: roughly 4,000–11,000 cells/µL.

High → often a bacterial infection; also stress, steroids, leukaemia.
Low → viral infections, some autoimmune conditions, chemotherapy.

Differential count — the WBC breakdown

Your report will split the WBC total into five subtypes. The short version:

Cell	What "high" usually means
Neutrophils	Bacterial infection
Lymphocytes	Viral infection
Monocytes	Chronic infection (e.g. TB)
Eosinophils	Allergy, parasites, asthma
Basophils	Rarely abnormal on its own

This is one of the most clinically useful parts of the CBC. If you have a fever and your neutrophils are sky-high, your doctor has a strong hint it's bacterial — not viral.

Platelet count

Normal: 150,000–450,000/µL.

Low platelets (thrombocytopenia) → bleeding risk. In India, dengue is the most famous cause of a sudden drop. Many viral illnesses cause a mild dip.
High platelets (thrombocytosis) → often reactive (inflammation, iron deficiency, after surgery). Persistently high needs investigation.

MPV (Mean Platelet Volume)

Size of the average platelet. Usually reported, rarely acted on alone — mostly a supporting clue.

Putting it together: three common patterns

Pattern 1 — "Classic iron deficiency"

Hb 10.2 ↓ · MCV 72 ↓ · MCH 22 ↓ · RDW 16 ↑

Low Hb, small cells, varied cell sizes. In India, especially in women, this almost always means iron deficiency. Next step: iron studies (ferritin, transferrin saturation).

Pattern 2 — "Viral infection"

WBC 4,200 · Lymphocytes 58% ↑ · Neutrophils 30% ↓ · Platelets 140,000 ↓

Lymphocyte-dominant WBC with a mild platelet drop is a classic viral signature — common cold, dengue, COVID, etc. Your doctor will look at symptoms and possibly order specific viral tests (NS1, etc.).

Pattern 3 — "Bacterial infection"

WBC 14,500 ↑ · Neutrophils 82% ↑ · Platelets 380,000

Neutrophil-heavy high WBC suggests bacterial infection. A course of antibiotics — chosen by your doctor based on where the infection is — is the usual answer.

What to ask your doctor

"Which number on this report is actually abnormal for me, and by how much?" Lab reference ranges don't account for age, pregnancy, or existing conditions.
"If haemoglobin is low, what type of anaemia do you think it is?" This determines whether you need iron, B12, folate, or further tests.
"Do I need a repeat CBC, and when?" Many mild abnormalities resolve on their own.