The CBC, or complete blood count, is one of the most common blood tests. Doctors order it in routine checkups and when you have fever, weakness or infection. This guide explains the main parts of a CBC report in simple words.
What is a CBC?
Your blood has three main types of cells:
- Red blood cells (RBC): carry oxygen from the lungs to the body
- White blood cells (WBC): fight infection
- Platelets: help blood clot and stop bleeding
A CBC counts these cells and checks their size and features. It is a simple blood test from a vein, and fasting is usually not needed.
Hemoglobin (Hb)
Hemoglobin is the protein in red blood cells that carries oxygen. It is the main value used to check for anemia (khoon ki kami).
Common adult ranges:
- Men: about 13 to 17 g/dL
- Women: about 12 to 15 g/dL
Low hemoglobin can cause tiredness, weakness, breathlessness, pale skin and dizziness. Common causes include iron deficiency, vitamin B12 or folate deficiency, blood loss and some long-term illnesses. Anemia is very common in Indian women and children.
High hemoglobin is less common. It can be seen with dehydration, smoking, living at high altitude or some medical conditions.
Red blood cell count and indices
The CBC also shows the RBC count and some "indices" that describe the red cells:
- Hematocrit (HCT or PCV): the share of blood made up of red cells
- MCV: the average size of red cells. Small cells are often seen in iron deficiency. Large cells are often seen in B12 or folate deficiency.
- MCH and MCHC: how much hemoglobin is in each red cell
- RDW: how much the red cells vary in size
These values help your doctor find the likely cause of anemia.
White blood cells (WBC)
A common adult range for total WBC count is about 4,000 to 11,000 cells per microlitre.
- High WBC is often seen with infections, inflammation, stress or after some medicines.
- Low WBC can happen with some viral infections, some medicines, or problems with the bone marrow.
The differential count shows the different types of WBC:
- Neutrophils: often rise in bacterial infections
- Lymphocytes: often rise in viral infections
- Eosinophils: may rise in allergies or worm infections
- Monocytes and basophils: smaller groups that your doctor will also look at
Platelets
A common adult range is about 1.5 to 4.5 lakh per microlitre (150,000 to 450,000).
Low platelets are often checked during fever, especially in dengue season. Low platelets can also be due to other infections, some medicines or other conditions. Very low counts can increase the risk of bleeding.
High platelets can be seen after infection, inflammation, iron deficiency or other conditions.
If you have fever with low platelets, follow your doctor's advice closely. Your doctor may ask you to repeat the CBC daily or every few days.
About reference ranges
The ranges above are common examples. Ranges differ a little between labs, and they are different for children, pregnant women and older adults. Always use the reference range printed on your report. A value slightly outside the range is often not a problem, but show your report to your doctor.
When is a CBC done?
- As part of a routine or full body checkup
- When you have fever, especially for more than 2 to 3 days
- When you feel tired, weak or breathless
- Before surgery
- During pregnancy
- To follow up on anemia or a known blood condition
How to prepare
- Fasting is usually not needed for CBC alone.
- If CBC is part of a package with fasting tests, follow the package instructions.
- Drink enough water so the sample is easy to collect.
- Tell your doctor about any medicines you take.
Frequently asked questions
Is hemoglobin of 11 low for a woman?
A hemoglobin of 11 g/dL is slightly below the usual adult female range, which suggests mild anemia. Your doctor may suggest more tests, such as iron studies or B12, to find the cause.
Can CBC detect dengue?
A CBC cannot confirm dengue on its own. It shows changes like low platelets and low WBC, which are common in dengue. Your doctor may order a separate dengue test.
How often should I do a CBC?
As part of a yearly checkup is common for healthy adults. If you have anemia, fever or another condition, your doctor will tell you how often to repeat it.
Book this test
You can book a CBC test, alone or in a health package, with home sample collection. Book a test or see all tests.
This article is for general information only and is not medical advice. Please talk to your doctor about your symptoms and report.
