Last revised by Dr Daniel J Bell on 04 Oct 2021

Anemia is the presence of reduced hemoglobin in the blood. Formally, the World Health Organizatiοn (WHO) defines anemia by the hemoglobin 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 etiology of anemia is traditionally categorized 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) anemias. 

Microcytic (MCV <82 fL)
Normocytic (MCV = 82-98 fL) 
Macrocytic (MCV >98 fL)

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