CBC Blood Test: What do your results mean?

However just because you get one abnormal result does not always mean you have a serious illness.

What is a CBC test?

A CBC provides information on the following three types of blood cells:

• Red blood cells (RBC) - they carry oxygen around the body.
• White blood cells (WBC) - help fight infection within our immune system.
• Platelets - help form blood clots.

It gives information on your haemoglobin levels, haematocrit and other RBC parameters which can give us useful information on your overall health and if further tests are required.

Why would a doctor recommend a CBC?

A CBC may be carried out as part of your regular health checks, or to help investigate certain symptoms or monitor a condition.

You may have a CBC if you:

• have unexplained fatigue, weakness or paleness
• have a fever or suspected infection
• are bruising easily or have abnormal bleeding
• to monitor certain medical conditions
• to see how well treatments are working that may affect your blood cells.

While a CBC can help identify possible causes it cannot diagnose all conditions.

Do you need to fast before a CBC test?

A fast is usually not required for a CBC. A blood sample will generally be taken from a vein in your arm and should take only a few minutes.

Before you have this test:

• Follow any advice given by the laboratory.
• Ask if you need to fast for any other tests carried out at the same time.
• Let them know about any medications that may affect your results.
• Take any medications as advised unless told otherwise by a member of clinical staff.

You may feel some mild soreness or bruising around where the needle was inserted.

What do the numbers on a CBC report mean?

When looking at the abbreviations they might seem confusing but here is what they mean:

Red blood cell results

These give an indication of how well the blood can carry oxygen, and also can be investigated if there is any anaemia.

• Hb = Haemoglobin (protein which carries oxygen in the red blood cells)
• RBC = Number of red blood cells in a set volume of blood.
• Hct = Percentage of blood that is red blood cells.
• MCV = Average size of red blood cells.
• MCH & MCHC = Indicates amount and concentration of Haemoglobin in red blood cells.
• RDW = Gives an indication of the variation in the size of red blood cells.

These values can help doctors investigate different types of anaemia.

White blood cell results

This is a measure of the white blood cell count. In some reports a breakdown of these white blood cells will be given. These are:

• Neutrophils – Help fight many bacterial and fungal infections.
• Lymphocytes – Include cells involved in immune system responses.
• Monocytes – Help get rid of germs and damaged cells.
• Eosinophils – Involved in allergies and some parasitic infections.
• Basophils – Involved in allergic and inflammatory responses.

There are many causes of an increased or decreased level and should be looked at along with any symptoms and other findings.

Platelet results

Platelets aid clotting.

• Low levels may lead to an increased risk of bleeding.
• High levels may be caused by inflammation, iron deficiency or other causes.
• MPV stands for mean platelet volume. This measures the average size of platelets.

A high or low platelet level alone does not give you any information as to what the cause is.

What do high or low CBC results mean?

If there is an abnormally high or low value then this will be shown by either an H or L. This does not necessarily mean you have a disease.

Possible causes could be:

• Low haemoglobin – Anaemia (can be caused by many things).
• High WBC – Infection, Inflammation, Certain medications, Other conditions.
• Low WBC – Certain infections, Medications, Bone Marrow disorders.
• High Haematocrit – Sometimes dehydration or other medical conditions.
• Abnormal Platelet Count – Inflammation, Nutritional Deficiencies or Other disorders.

Doctors will look at the overall picture, history of any medical conditions and further tests if required.

When should a CBC report be discussed with a doctor?

Consult a doctor if CBC results are repeatedly abnormal or accompanied by symptoms such as persistent tiredness, frequent infections, unusual bruising, or prolonged bleeding.

Seek immediate medical attention for severe symptoms, including chest pain, difficulty breathing, or heavy, uncontrolled bleeding.

Need help understanding a CBC report?

Medical acronyms can sometimes be confusing. However, YourDoc has an AI-powered healthcare assistant, Jivika will help to educate you on some commonly used medical terminology. This will help you understand your CBC results. If you need any further medical advice, YourDoc offers instant video consultations with online doctors so you can get expert advice from a qualified doctor on your symptoms, results and next steps.

Note: Always consider your medical history, symptoms and a doctor's opinion when interpreting your CBC report.

The bottom line

A CBC gives useful information about your red blood cells, white blood cells and platelets. An abnormal result just indicates that there may be a problem. Other factors such as the reference range from the laboratory, your symptoms, previous medical history and other tests will all need to be considered.