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Complete blood count (CBC)

A complete blood count, shortened as CBC, is a common screening test that helps diagnose several health issues. A CBC checks if there is an increase or decrease in your blood cell counts. The normal CBC values depend on your gender and age.

A CBC test helps to diagnose a wide range of conditions, including infection, anaemia and cancer.

The basic blood cell types

Your blood cell count can help your healthcare provider detect disorders and evaluate your overall health. It measures three basic blood cells. They include:

Why get a CBC?

Your healthcare provider may order a CBC during your routine health check or if you experience unexplained symptoms such as bruising or bleeding. Complete blood count helps your doctor:

How to prepare for a CBC

Ensure you wear a shirt with a short sleeve or a sleeve you can easily roll up. You can eat before a CBC, but your healthcare professional may advise fasting for a specific period before the test. This may be the case if you need additional testing.

What happens during a CBC?

During your CBC, the healthcare professional will draw blood from your vein, usually from the back of your hand or inside your elbow. This takes only a few minutes with the following steps. The provider will:

The blood draw may be slightly uncomfortable. You may feel a pinching or prick when the needle enters your skin. Some people feel light-headed or faint at the sight of blood. After the blood draw, minor bruising may occur, but this clears within a few days.

You can get your CBC result within a few hours or a day after the testing.

Result Interpretation

The test results vary based on sex. The following are the normal result range for adults, but the figures may vary slightly for different labs.

Blood component

Normal levels

Red blood cell count

Men: 4.32 – 5.72 million cells/mcL

Women: 3.90 – 5.03 million cells/mcL

White blood cell count

3500 – 10500 cells/mcL

Platelet count

150000 – 450000 cells/mCL


Men: 38.8 – 50.0%

Women: 34.9 – 44.5%


Men: 135 – 175 grams/L

Women: 120 – 155 grams/L

A complete blood count doesn’t give a definite diagnosis. A low or high blood count could indicate a wide range of conditions, so you will need specialised tests for a specific diagnosis.

Conditions that may cause abnormal complete blood count include:

If your CBC is below or above the normal range, the doctor may order additional tests to confirm your results. Further tests may also be necessary to confirm a diagnosis and evaluate your condition.

You can get a complete blood count test at Private Blood Tests London. Our healthcare professionals can advise you on the test needed. Visit our clinic today or call 02071830244 to schedule an appointment for your CBC test.