Complete blood count (CBC): normal ranges and results (BKT)

A complete blood count (CBC), also called a haematology test or an automated blood count, counts and describes the three main groups of blood cells from a single sample. These are red blood cells (erythrocytes, which carry oxygen), white blood cells (leukocytes, responsible for the immune response) and platelets (thrombocytes, the cells needed for blood clotting). Alongside the cell counts, the test assesses the haemoglobin level (the protein inside red cells that carries oxygen) and the haematocrit (the share of red cells in the blood volume). This is one of the most frequently performed laboratory tests, both at a preventive check-up and when illness is suspected, because it can show anaemia, infection, inflammation, blood clotting disorders or changes in bone marrow activity at the same time. Results are usually presented as a list of separate indicators (red cells, white cells, platelets, haemoglobin, haematocrit and others), each with its own reference limits.

• As part of a preventive health check, even without any complaints
• With tiredness, weakness, dizziness or shortness of breath — when anaemia is suspected
• With a fever or other signs of infection — to assess the white blood cell count
• When unusual bruising, bleeding or poor healing appears — to assess platelets
• To monitor a chronic illness, or the effect of treatment (for example chemotherapy) on blood counts
• Before planned surgery, or as part of a broader health assessment

In a complete blood count, some indicators have a lower reference limit for women than for men, and several are wider or higher for men. According to the MedlinePlus medical encyclopedia, the red blood cell range for women is 4.2–5.4 ×10¹²/l (men 4.6–6.2 ×10¹²/l), haemoglobin 120–160 g/l (men 130–180 g/l) and haematocrit 36–48 % (men 40–55 %). The white blood cell (4.5–11 ×10⁹/l) and platelet (150–400 ×10⁹/l) ranges are given in the source without splitting by sex.

In a complete blood count, what a raised result means depends on which group of blood cells is out of range. Raised red blood cells, haemoglobin or haematocrit can point to dehydration, a chronic lack of oxygen or polycythaemia. Raised white blood cells are most often linked to infection or inflammation. Raised platelets can point to bleeding, iron deficiency or a bone marrow disorder.

• Dehydration — red blood cell, haemoglobin and haematocrit values rise relatively
• A chronic lack of oxygen (for example due to lung disease) or kidney disease — can raise the red blood cell count
• Infection, inflammation, lupus or tissue damage — raises the white blood cell count
• Iron deficiency, bleeding or bone marrow disorders — can raise the platelet count
• Smoking or testosterone use — can raise red blood cell and haemoglobin values

Alongside a raised result, a doctor usually assesses:

• Which specific indicator (red cells, white cells or platelets) is out of range — the other possible causes differ
• Whether dehydration or a recent infection could have temporarily affected the result
• Further tests (a white cell differential, inflammation markers) to establish the cause more precisely
• When it is worth repeating the test so that a change over time becomes visible

A low result

Low red blood cells, haemoglobin or haematocrit most often indicate anaemia, which can be caused by blood loss, iron deficiency or impaired bone marrow function. Low white blood cells can indicate an autoimmune disease or a bone marrow disorder, or be a consequence of chemotherapy. Low platelets are linked to an increased risk of bleeding.

• Blood loss, iron deficiency or poor nutrition — lowers red blood cells, haemoglobin and haematocrit
• Bone marrow failure, haemolysis, chronic kidney disease or cancer — can lower red blood cell values
• Alcohol misuse, autoimmune diseases, viral infections or liver/spleen disease — can lower white blood cells
• Chemotherapy or other treatments that suppress bone marrow activity — can lower both white blood cells and platelets
• An enlarged spleen or disorders of platelet breakdown — can lower the platelet count

Symptoms that can accompany a low result: tiredness or weakness, shortness of breath, dizziness, bruising or increased bleeding.

Alongside a low result, a doctor usually assesses:

• Which specific indicator is low — the further tests needed depend on that
• Iron markers (iron, ferritin) — if iron deficiency anaemia is suspected
• The history of medicines and treatment — some medicines can temporarily lower blood cell counts
• When it is worth repeating the test to assess the change

At the Medicina practica laboratory, a complete blood count costs from €10 (September 2026 pricing). A family doctor can also order the test free of charge when there are indications. Separate pages cover haemoglobin and how to read blood test results.