Complete blood count (CBC): the routine blood test explained

A complete blood count measures red cells, white cells, platelets and haemoglobin. Why Indian hospitals ask for it, what it shows and how to send results.

Glossary term · Tests & reports

By Nikhil Sharma, Founder · Updated · How we write and check

Definition

Complete blood count (CBC) (also: CBC, Full blood count, FBC, Haemogram): A complete blood count is a blood test that measures red blood cells, white blood cells, platelets, haemoglobin and haematocrit.

A complete blood count, or CBC, measures the main parts of your blood. MedlinePlus lists red blood cells, white blood cells, platelets, haemoglobin and haematocrit. It is often part of a routine check-up. MedlinePlus also lists it among the common blood tests before surgery, so expect to be asked for a recent result.

What does each part show?

  • Red blood cells carry oxygen from the lungs to the body.
  • White blood cells fight infections and other diseases.
  • Platelets help the blood to clot.
  • Haemoglobin is the protein in red cells that carries oxygen.
  • Haematocrit is the share of the blood made up of red cells.

Why is it used?

MedlinePlus says a CBC is often part of a routine check-up and helps diagnose and monitor anaemia, infections, immune disorders and blood cancers. MedlinePlus also lists a CBC among common blood tests before surgery.

How do I prepare?

Usually no preparation is needed. If other tests are taken from the same sample, you may need to fast.

Reading the results

MedlinePlus notes that a result outside the normal range does not always mean a condition that needs treatment. Diet, activity, medicines, menstruation and dehydration can affect results. Your doctor interprets them alongside other information.

When sending results

Send the full report with the units and the laboratory’s reference ranges. Ranges vary between laboratories.

Questions people ask

How recent should my CBC be?

Before a procedure, the hospital may repeat the test on arrival. For a first remote review, ask the hospital how recent a result it needs before you pay for a new test.

What is a CBC with differential?

It also counts the five types of white blood cells. Your specialist may ask for it when looking for infection, inflammation or blood disorders. MedlinePlus notes that a standard CBC gives the total white cell count only.

Sources

General information, not medical or legal advice. Rules change: confirm with the official source. Your treating specialist decides on suitability, treatment and length of stay. How we write and check.

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