Anaemia is defined as a low level of haemoglobin in the blood. This is the result of an underlying disease and is not a disease itself. The prefix an- means without and the suffix aemia refers to blood.

Haemoglobin is a protein found in red blood cells. It is responsible for picking up oxygen in the lungs and transporting it to the cells of the body. Iron is an essential ingredient in creating haemoglobin and forms part of the structure of the molecule. When a patient has a low level of haemoglobin they have a condition called anaemia.

You can diagnose a patient with anaemia when they have a low haemoglobin. When you find an anaemic patient you should check the mean cell volume (MCV). This is the size of the red blood cells. The normal ranges are:


Mean Cell Volume (MCV)


120 – 165 grams/litre

80-100 femtolitres


130 -180 grams/litre

80-100 femtolitres

Anaemia is initially subdivided into three main categories based on the size of the red blood cell (the MCV). These have different underlying causes:

  • Microcytic anaemia (low MCV indicating small RBCs)
  • Normocytic anaemia (normal MCV indicating normal sized RBCs)
  • Macrocytic anaemia (large MCV indicating large RBCs)


Microcytic Anaemia Causes

A helpful mnemonic for understanding the causes of microcytic anaemia is TAILS.

  • TThalassaemia
  • AAnaemia of chronic disease
  • IIron deficiency anaemia
  • LLead poisoning
  • SSideroblastic anaemia


Normocytic Anaemia Causes

There are 3 As and 2 Hs for normocytic anaemia:

  • AAcute blood loss
  • AAnaemia of Chronic Disease
  • AAplastic Anaemia
  • HHaemolytic Anaemia
  • HHypothyroidism


Macrocytic Anaemia Causes

Macrocytic anaemia can be megaloblastic or normoblastic. Megaloblastic anaemia is the result of impaired DNA synthesis preventing the cell from dividing normally. Rather than dividing it keeps growing into a larger, abnormal cell. This is caused by a vitamin deficiency.


Megaloblastic anaemia is caused by:

  • B12 deficiency
  • Folate deficiency


Normoblastic macrocytic anaemia is caused by:

  • Alcohol
  • Reticulocytosis (usually from haemolytic anaemia or blood loss)
  • Hypothyroidism
  • Liver disease
  • Drugs such as azathioprine


Symptoms of Anaemia

There are many generic symptoms of anaemia:

  • Tiredness
  • Shortness of breath
  • Headaches
  • Dizziness
  • Palpitations
  • Worsening of other conditions such as angina, heart failure or peripheral vascular disease


There are symptoms specific to iron deficiency anaemia:

  • Pica describes dietary cravings for abnormal things such as dirt and can signify iron deficiency
  • Hair loss can indicate iron deficiency anaemia


Signs of Anaemia

Generic signs of anaemia:

  • Pale skin
  • Conjunctival pallor
  • Tachycardia
  • Raised respiratory rate


Signs of specific causes of anaemia:

  • Koilonychia is spoon shaped nails and can indicate iron deficiency
  • Angular chelitis can indicate iron deficiency
  • Atrophic glossitis is a smooth tongue due to atrophy of the papillae and can indicate iron deficiency
  • Brittle hair and nails can indicate iron deficiency
  • Jaundice occurs in haemolytic anaemia
  • Bone deformities occur in thalassaemia
  • Oedema, hypertension and excoriations on the skin  can indicate chronic kidney disease

Investigating Anaemia

Initial Investigations:

  • Haemoglobin
  • Mean Cell Volume (MCV)
  • B12
  • Folate
  • Ferritin
  • Blood film


Further Investigations:

  • Oesophago-gastroduodenoscopy (OGD) and colonoscopy to investigate for a gastrointestinal cause of unexplained iron deficiency anaemia. This is done on an urgent cancer referral for suspected gastrointestinal cancer.
  • Bone marrow biopsy may be required if the cause is unclear


Last updated April 2019