Dr Daniel J Bell et al.

Anaemia is the presence of reduced haemoglobin in the blood. Formally, the World Health Organization (WHO) defines anaemia by the haemoglobin concentration in the blood according to age and sex 1:

  • adult men: <130 g/L
  • adult women: <120 g/L

Values for pregnant women and children are different.



The aetiology of anaemia is traditionally categorised by the volume of the red cell, i.e. the mean cell volume (MCV), into microcytic (MCV <82 fL), normocytic (MCV = 82-98 fL) and macrocytic (MCV >98 fL) anaemias. 

Microcytic (MCV <82 fL)
Normocytic (MCV = 82-98 fL) 
Macrocytic (MCV >98 fL)
  • dietary deficiency: vitamin B12, folate
  • medication toxicity: hydroxyurea, AZT, methotrexate
  • dyserythropoiesis, myelodysplastic syndrome, clonal haematologic disorder
  • hereditary haematologic disorders
Share article

Article information

rID: 64273
System: Haematology
Section: Pathology
Synonyms or Alternate Spellings:
  • Anemias
  • Anemia
  • Anaemias

Support Radiopaedia and see fewer ads

Updating… Please wait.

Alert accept

Error Unable to process the form. Check for errors and try again.

Alert accept Thank you for updating your details.