Intended for healthcare professionals

Practice Rational Testing

Investigating microcytic anaemia

BMJ 2013; 346 doi: (Published 07 June 2013) Cite this as: BMJ 2013;346:f3154
  1. W Owen Uprichard, general practitioner1,
  2. James Uprichard, consultant haematologist2
  1. 1Leicestershire, UK
  2. 2St George’s Healthcare NHS Trust, Haematology Department, London SW17 0QT, UK
  1. Correspondence to: J Uprichard j.uprichard{at}

This article explores how to assess the common causes of microcytic anaemia

Learning points

  • Iron deficiency anaemia and thalassaemia trait are the commonest causes of microcytic anaemia, but they may coexist

  • Serum ferritin and haemoglobin A2 quantitation are the two most important investigations to distinguish between iron deficiency anaemia and thalassaemia trait

  • Failure of iron deficiency anaemia to respond to oral iron supplementation may be due to poor adherence, malabsorption, continued blood loss, or the presence of a concurrent disorder such as thalassaemia trait or anaemia of chronic disease

A 27 year old Pakistani housewife presented with tiredness. She attributed some of this to looking after her 18 month old twins, born in Pakistan where she had received her antenatal care, but wondered if there might be another cause. She consumed a mixed diet, took no drugs or supplements, and had no anorexia, weight loss, gastrointestinal symptoms, or menorrhagia. A physical examination revealed pallor of the conjunctivae, but the findings were otherwise unremarkable. Anaemia was suspected.

A full blood count showed haemoglobin 86 g/L (reference range 110-140 g/L), mean cell volume 68 fL (76-96 fL), mean cell haemoglobin 22 pg (27-32 pg), white cell count 8×109/L (4-11×109/L), and platelet count 460×109/L (150-400×109/L).

What are the causes of microcytic anaemia?

Anaemia with a reduced mean cell volume is usually due to iron deficiency (table 1) or in certain ethnic groups, thalassaemia trait1 (table 2). Less commonly it may be due to sideroblastic anaemia or to anaemia of chronic disease (a hypoproliferative anaemia, often with raised inflammatory markers and occurring in response to infection, inflammation, or malignancy).2 Different anaemias, with distinguishing features, may coexist (table 3).

View this table:
Table 1

 Groups at risk of iron deficiency anaemia, prevalence, and reasons3-8

View this table:
Table 2

 Prevalence of thalassaemia trait in the United Kingdom according …

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