Complete Blood Count (CBC)
The Complete Blood Count (CBC), also known as a Full Blood Count (FBC) in some countries, is one of the most commonly requested laboratory investigations. It provides valuable information about oxygen-carrying capacity, immune activity, blood cell production, and overall physiological status.
Changes in CBC markers do not necessarily indicate disease. Nutrition, hydration, infection, inflammation, medications, physical activity, altitude, and underlying medical conditions may all influence results.
Important
Individual blood cell markers should always be interpreted together. A single abnormal value rarely provides a complete clinical picture.
Red Blood Cells (RBC)
What it reflects
Red blood cells transport oxygen from the lungs to tissues and return carbon dioxide to the lungs for elimination.
Why it matters
RBC count helps assess oxygen transport capacity and may provide clues to anaemia, dehydration, nutritional deficiencies, or disorders affecting red blood cell production.
Reference values
Typical laboratory reference range
Men: approximately 4.5–5.9 ×10¹²/L
Women: approximately 4.0–5.2 ×10¹²/L
Integra perspective
RBC count should always be interpreted alongside haemoglobin, haematocrit, and red blood cell indices rather than as an isolated measurement.
Interpret together with
• Haemoglobin
• Haematocrit
• MCV
Haemoglobin (Hb)
What it reflects
Haemoglobin is the oxygen-carrying protein contained within red blood cells.
Why it matters
Haemoglobin provides one of the most useful indicators of oxygen transport and is central to the assessment of anaemia.
Reference values
Typical laboratory reference range
Men: approximately 135–175 g/L
Women: approximately 120–155 g/L
Integra perspective
Low haemoglobin should prompt investigation into potential causes rather than being viewed as a diagnosis itself. Iron status, vitamin B12, folate, chronic inflammation, and kidney function all influence haemoglobin production.
Interpret together with
• RBC
• Haematocrit
• Ferritin
• Vitamin B12
Haematocrit (Hct)
What it reflects
Haematocrit represents the proportion of blood volume occupied by red blood cells.
Why it matters
It provides additional information regarding hydration status, oxygen-carrying capacity, and red blood cell concentration.
Reference values
Typical laboratory reference range
Men: approximately 40–52%
Women: approximately 36–46%
Integra perspective
Haematocrit is strongly influenced by hydration status. Mild elevations may simply reflect dehydration, while lower values may accompany anaemia or fluid overload.
Interpret together with
• RBC
• Haemoglobin
• Hydration status
Mean Corpuscular Volume (MCV)
What it reflects
MCV measures the average size of individual red blood cells.
Why it matters
MCV assists in identifying the likely cause of anaemia and certain nutritional deficiencies.
Reference values
Typical laboratory reference range
Generally 80–100 fL.
Integra perspective
Low MCV commonly suggests iron deficiency, while elevated MCV may indicate vitamin B12 or folate deficiency, alcohol excess, liver disease, or other metabolic conditions. Interpretation should always include additional laboratory markers.
Interpret together with
• Haemoglobin
• Ferritin
• Vitamin B12
• Folate
White Blood Cells (WBC)
What it reflects
White blood cells form part of the body's immune system and help defend against infection, inflammation, and tissue injury.
Why it matters
Changes in total white blood cell count may reflect immune activation, infection, inflammation, physiological stress, medications, or bone marrow disorders.
Reference values
Typical laboratory reference range
Generally 4.0–11.0 ×10⁹/L.
Integra perspective
An isolated WBC result should never be interpreted independently. Differential white blood cell counts often provide considerably more useful clinical information.
Interpret together with
• Neutrophils
• Lymphocytes
• hs-CRP
Neutrophils
What it reflects
Neutrophils are the most abundant white blood cells and form the first line of defence against bacterial infection and acute inflammation.
Why it matters
Neutrophil counts commonly rise during bacterial infections, acute physiological stress, corticosteroid use, and inflammatory conditions.
Reference values
Typical laboratory reference range
Generally 2.0–7.5 ×10⁹/L.
Integra perspective
Temporary fluctuations are common and should always be interpreted alongside total white blood cell count, lymphocytes, symptoms, and clinical history.
Interpret together with
• WBC
• Lymphocytes
• hs-CRP
Lymphocytes
What it reflects
Lymphocytes are specialised immune cells involved in antiviral defence, antibody production, and long-term immune regulation.
Why it matters
Changes in lymphocyte count may reflect viral infections, immune disorders, chronic physiological stress, or certain medications.
Reference values
Typical laboratory reference range
Generally 1.0–4.0 ×10⁹/L.
Integra perspective
The balance between neutrophils and lymphocytes often provides more useful clinical information than either marker alone.
Interpret together with
• WBC
• Neutrophils
• Clinical symptoms
Platelets
What it reflects
Platelets are small blood components responsible for blood clotting, tissue repair, and vascular integrity.
Why it matters
Platelet abnormalities may reflect inflammation, iron deficiency, infection, bone marrow disorders, or disorders affecting clotting.
Reference values
Typical laboratory reference range
Generally 150–400 ×10⁹/L.
Integra perspective
Platelet count should always be interpreted within the wider clinical picture. Mild variations are common and are often temporary.
Interpret together with
• CBC
• Ferritin
• hs-CRP
Looking at the Whole Picture
No individual CBC marker provides a complete assessment of health.
For example:
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Low haemoglobin may result from iron deficiency, vitamin deficiencies, chronic disease, or impaired red blood cell production.
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Elevated haematocrit may simply reflect dehydration rather than increased red blood cell production.
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MCV helps identify potential nutritional deficiencies but requires confirmation with additional laboratory testing.
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Elevated white blood cells often reflect infection or inflammation but may also occur following physical stress or medication use.
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Neutrophil and lymphocyte patterns frequently provide more useful information than total white blood cell count alone.
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Platelet changes should always be interpreted alongside inflammatory markers, iron studies, and the remainder of the CBC.
Recognising patterns across the complete blood count provides considerably more clinical insight than interpreting isolated results.
Core Principle
The Complete Blood Count provides a broad overview of oxygen transport, immune function, inflammation, and blood cell production.
Rather than focusing on isolated abnormalities, the greatest clinical value comes from understanding how individual blood cell markers interact with one another and with the wider metabolic, nutritional, and inflammatory context.