How to Read a CBC Report: Your Complete Blood Count Explained
Got a CBC report full of numbers? Learn what haemoglobin, WBC, platelets, haematocrit and MCV mean, why results vary, and when to see a doctor.
Status: Pending Qualified Medical Review. This article has not yet been reviewed by a qualified medical professional.
The CBC — complete blood count — is probably the most common blood test in Bangladesh. Doctors order it for fever, tiredness, dengue, pregnancy check-ups, before surgery, and as part of routine health checks. Then the report arrives with a long list of short forms: Hb, RBC, WBC, PLT, HCT, MCV, ESR. Some numbers are in bold or marked "H" or "L".
This guide explains each main part of a CBC in plain language, so you know what you are looking at before you speak to your doctor.
What Is a CBC?
According to the US National Library of Medicine (MedlinePlus), a complete blood count is a group of blood tests that measure the number and size of different cells in your blood. It is also called a full blood count or blood cell count.
A CBC is used:
- As part of a routine check-up
- To help diagnose infections, anaemia, blood disorders and immune problems
- To monitor a condition or treatment that affects blood cells
Do I need to fast?
Usually no special preparation is needed for a CBC. If other tests are done on the same sample (such as fasting sugar or lipids), you may need to fast. Follow your doctor's instructions.
The Most Important Rule: Use Your Lab's Reference Range
Every CBC report has a column called "reference range", "normal value" or "biological reference interval". Normal ranges are different for men, women, children and pregnant women, and also vary a little between labs and machines.
So always compare your result to the range printed on your own report, not to a number from the internet or a friend's report.
Parts of a CBC Report
1. Haemoglobin (Hb)
What it is: An iron-rich protein in red blood cells that carries oxygen from the lungs to the body (MedlinePlus).
Low haemoglobin can mean anaemia. Common causes include low iron, heavy periods, pregnancy, blood loss, poor diet, worm infections, and inherited conditions such as thalassaemia.
Example: Farzana, 26, feels tired and breathless on the stairs. Her Hb is below the lab's range and marked "L". Her doctor suspects iron deficiency and orders more tests.
2. Red blood cell count (RBC)
What it is: The number of red blood cells, which carry oxygen.
Abnormal RBC, haemoglobin or haematocrit may be a sign of dehydration, anaemia, heart disease or too little iron, according to MedlinePlus.
3. Haematocrit (HCT) or Packed Cell Volume (PCV)
What it is: The share of your blood made up of red blood cells.
- High HCT can be seen with dehydration — the blood becomes more concentrated.
- In dengue, doctors watch the haematocrit closely. A rise can suggest fluid leaking from blood vessels, especially when platelets are falling fast.
- Low HCT often goes with anaemia.
4. Red cell indices: MCV, MCH, MCHC, RDW
These describe the size and colour of red blood cells. MedlinePlus describes MCV as the average size of red blood cells.
- Low MCV (small cells) is often seen in iron deficiency and thalassaemia trait
- High MCV (large cells) can be linked with low vitamin B12 or folate, and some other causes
These numbers help your doctor decide which type of anaemia you may have and what further tests are needed.
5. White blood cells (WBC) — total count
What they are: Cells that fight infection and disease.
MedlinePlus explains:
- A high WBC count may be a sign of an infection or a reaction to a medicine
- A low WBC count can have several causes, including some viral infections, autoimmune conditions, bone marrow problems or, rarely, cancer
In dengue, a low WBC count is common.
6. Differential count (DC)
This breaks the WBC down into five types. A CBC "with differential" measures each:
- Neutrophils — often raised in bacterial infections
- Lymphocytes — often change in viral infections
- Eosinophils — can rise with allergies, asthma or worm infections
- Monocytes and basophils — smaller groups
Your doctor reads these patterns together with your symptoms.
7. Platelets (PLT)
What they are: Small cells that help blood clot and stop bleeding.
- Low platelets are common in dengue and some other infections, and can be caused by certain medicines or blood disorders
- High platelets can occur after infection, inflammation, iron deficiency or other conditions
In dengue, the trend over several tests matters more than one number.
8. ESR (often added)
Many labs in Bangladesh print ESR (erythrocyte sedimentation rate) with the CBC. It is a general marker of inflammation. A high ESR is not specific — it can rise with infection, inflammation, pregnancy, anaemia and age. It needs to be read with other findings.
"My Report Has Some Abnormal Numbers — Should I Worry?"
Not always. MedlinePlus notes that an abnormal level does not always mean you have a condition that needs treatment. Results can be affected by:
- Diet
- Activity level
- Medicines
- Menstrual period
- Not drinking enough water
A CBC is only one tool. Your doctor considers your history, symptoms and other tests.
When to contact a doctor soon
- Several values are flagged high or low
- You have symptoms: tiredness, breathlessness, fever, easy bruising, bleeding gums, frequent infections
- You are pregnant and Hb is low
- You have dengue and platelets are falling or haematocrit is rising
Go to hospital immediately or call 999 if you have:
- Heavy bleeding, vomiting blood or black stool
- Severe breathlessness or chest pain
- Fainting or confusion
- Dengue warning signs such as severe belly pain, repeated vomiting or bleeding
Tips for Sharing a CBC Report With a Doctor
- Photograph the whole page flat, in good light, so every number and the reference range is readable
- Include the date and patient age and sex
- If you have older reports, share them too — trends help
- Mention symptoms and medicines you take
- Say if you are pregnant, have thalassaemia in the family, or have dengue
Related reading: For more on dengue blood results, see dengue platelet count explained. If your CBC was ordered for a fever, read fever in adults: when to see a doctor.
Frequently Asked Questions
What does a CBC test show?
It measures red cells, white cells, platelets, haemoglobin, haematocrit and red cell size. It helps detect anaemia, infection and blood disorders.
What is a normal CBC range?
It depends on age, sex and lab. Always use the reference range printed on your own report.
Does a CBC detect cancer?
A CBC can show changes that suggest some blood problems, but it cannot diagnose most cancers on its own. Further tests are needed if a doctor is concerned.
Can dehydration affect CBC?
Yes. Dehydration can make haemoglobin and haematocrit look higher than usual.
How long does a CBC take?
The blood draw takes a few minutes. Most labs deliver results the same day.
Does a CBC show thalassaemia?
It can give clues, such as small red cells, but special tests like haemoglobin electrophoresis are needed to confirm.
Have Your CBC Report Reviewed on ShifaMate
If you have a CBC report and want to understand it, you can consult a verified doctor through ShifaMate. Upload a clear photo of the report in the app and describe your symptoms. The doctor can explain the results and suggest whether more tests or in-person care are needed. You can also browse ShifaMate doctors.
For heavy bleeding, fainting or dengue warning signs, go to hospital immediately.
References
- MedlinePlus (US National Library of Medicine, NIH). Complete Blood Count (CBC)
- NHS. Blood tests
- Directorate General of Health Services, Bangladesh
This article is for general information and does not replace advice from a qualified doctor.
Sources
This article is general health information, not medical advice for any individual. For your own situation, consult a registered doctor. In an emergency, go to the nearest hospital without delay.
