Overview The World Health Organization defines anaemia as a haemoglobin (Hb) concentration below 13 g/dl (130 g/L) in men over 15 years of age, below 12 g/dl (120g/L) in non-pregnant women over 15 years of age, and below 11 g/dl (110g/L) in pregnant women. There are many causes of anaemia. It is important to take a comprehensive history, examination and inspect FBC and blood films

Remember Anaemia men: 130g/L and in women: 120g/L

Physiology of RBCs

Watch: Haematology - Red Blood Cells


Watch: Haematology - RBC life cycle


  • History
    • Symptoms of Anaemia (fatigue, shortness of breath)
    • Sleeping - Obstructive sleep Apnoea
    • Pancytopaenia (easy bruising, bleeding, infections)
    • Family History of haemolytic disease
    • Menstrual history: menorrhagia, menometrorrhagia
    • Connective Tissue disorder
    • Neurological symptoms
    • Medication history
    • Ethnic background
    • Medical condition
    • Surgical history - heart valve surgery associated with haemolysis
  • Examination
    • Jaundice
    • Pallor
    • Splenomegaly
    • Hepatomegaly
    • Signs of connective tissue disease

Investigations If anaemia is suspected begin with:

  • Full blood examination
  • Iron studies
  • Serum vitamin B12/folate
  • Peripheral Blood film
  • Reticulocyte count
Reticulocytes are immature erythrocytes and are markers of erythrocyte production. The reticulocyte count should always be interpreted in the context of the Hb. Should normally increase when there is a decrease in RBC
  1. The first step in diagnosing the cause of anaemia is to find out the mean cell volume (MCV). The initial classification is based on the MCV:
    • Microcytic Anaemia
    • Normocytic Anaemia
    • Macrocytic Anaemia
  2.  Any further investigations will be determined by the blood film appearance and clinical suspicion
Microcytic Anaemia Normocytic Anaemia Macrocytic Anaemia
Iron-deficiency Anaemia of chronic disease (MCV may be reduced) Vitamin B12 deficiency
Thalasaemia Haemolytic anaemia (hemolysis) Alcohol excess
Sideroblastic anaemia Acute blood loss Reticulocytosis
Bone marrow failure/CKD Myelodysplastic syndrome
Hypothyroidism Myeloproliferative disorders
Pregnancy Hypothyroidism
Folate deficiency
Side Note Bone marrow failure induced anaemia is also known as Aplastic Anaemia