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A haemoglobin level less than expected for the individual’s age and sex. There are many causes, which are often identifiable by history, examination and inspection of the blood film.

  • Normal range for haemoglobin: men 13–18 g/dl; women 11.5–16 g/dl
  • MCV = mean corpuscular (cell) volume = average size of the red blood cells; normal range = 80–99 femtolitres

Anaemia with low MCV (microcytic)

May be caused by:

  • Iron deficiency (most common cause of anaemia in the UK)
  • Thalassaemia
  • Haemoglobinopathy

Anaemia with normal MCV (normocytic)

May be caused by:

  • Acute blood loss
  • Haemolysis (congenital or acquired) (mcv may be raised)
  • Pregnancy
  • Chronic disease
  • Bone marrow failure (e.g., aplastic anaemia, leukaemia)
  • Uraemia (renal failure)
  • Thyroid disease (mcv may be raised)
  • Haemoglobinopathy

Anaemia with raised MCV (macrocytic)

May be caused by:

  • B12 or folate deficiency
  • Thyroid disease
  • Alcohol
  • Liver disease
  • Reticulocytosis
  • Myelodysplasia
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