Anaemia: what to test and common causes

Anaemia is a finding, not a diagnosis

Anaemia means haemoglobin below the reference range, causing tiredness, breathlessness, palpitations or dizziness. Causes range from iron and vitamin deficiency, inherited blood disorders and chronic blood loss to certain chronic diseases.

Taking iron without knowing the cause may not help and can mask the real problem, so the cause should be investigated first.

Tests usually started first

The first step confirms anaemia and examines the size and shape of red cells.

• Complete blood count (CBC) for haemoglobin and red cell size
• Blood iron testing with assessment of iron deficiency where indicated
• Stool testing for occult blood if chronic blood loss is possible
• Haemoglobin typing (Hb typing) when an inherited disorder such as thalassaemia is suspected

What red cell size tells you

Doctors use red cell indices such as MCV to narrow down the cause. Small cells with anaemia may relate to iron deficiency or thalassaemia, while larger cells may relate to vitamin B12 or folate deficiency, alcohol, or other conditions.

This grouping helps doctors choose targeted follow-up tests and avoid unnecessary investigations.

When to see a doctor

See a doctor if tiredness persists, if you have unusual bleeding, heavy periods, weight loss or a family history of blood disorders, or if haemoglobin does not improve despite taking iron.

Treating anaemia effectively means treating the cause, which a doctor will plan from your results and history.