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What is it?

Anaemia is a condition that occurs when the number of red blood cells (RBCs) and/or the amount of haemoglobin found in the red blood cells drops below normal. Red blood cells and the haemoglobin contained within them are necessary for the transport and delivery of oxygen from the lungs to the rest of the body. Without a sufficient supply of oxygen, many tissues and organs throughout the body can be adversely affected. Anaemia can be mild, moderate or severe depending on the extent to which the RBC count and/or haemoglobin levels are decreased. It is a fairly common condition, affecting both men and women of all ages, races and ethnic groups. However, certain people are at an increased risk of developing anaemia. These include people with diets poor in iron and vitamins, chronic diseases such as kidney disease, diabetes, cancer, inflammatory bowel disease, a family history of inherited anaemia, chronic infections such as tuberculosis or HIV, and those who have had significant blood loss from injury or surgery.


In general, anaemia has two main causes:

  • Impaired or decreased production of RBCs as, for example, in iron deficiency, B vitamin deficiencies and aplastic anaemia
  • Decreased red cell survival, increased destruction of red blood cells as in haemolytic anaemia


There are several different types of anaemia and various causes. Some of the most common types are summarised in the table below. Click on the links to read more about each one.

Iron deficiencyLack of iron leads to decreased amount of haemoglobin; low levels of haemoglobin in turn leads to decreased production of normal RBCsBlood loss; diet low in iron; poor absorption of iron
Pernicious anaemia and B vitamin deficiencyLack of B vitamins does not allow RBCs to grow and then divide as they normally would during development; leads to decreased production of normal RBCsLack of intrinsic factor (pernicious anaemia, atrophic gastritis); diet lwo in B vitamins; decreased in absorption of B vitamins
AplasticDecreased production of all cells produced by the bone marrow of which RBCs are one typeCancer therapy; exposure to toxins; autoimmune disorders; viral infections
HaemolyticRBCs survive less than the normal 110-120 days in the circulation; leads to overall decreased numbers of RBCsInherited causes include sickle cell and thalassaemia; other causes include transfusion reaction, autoimmune disease, certain drugs (e.g. penicillin).
Anaemia of chronic diseasesVarious conditions over the long term can cause decreased production of RBCsKidney disease, diabetes, tuberculosis or HIV


Anaemia may be acute or chronic. Chronic anaemia may develop slowly over a period of time with long-term illnesses such as diabetes, chronic kidney disease or cancer. In these situations, the anaemia may not be apparent because symptoms are masked by the underlying disease. The presence of anaemia in chronic conditions may often go undetected for a period of time and sometimes may only be discovered during tests or examinations for other conditions.


Anaemia may also occur in acute episodes such as with certain haemolytic anaemias in which a significant number of RBCs are destroyed. Signs and symptoms may become apparent very quickly and the cause determined from a combination of physical examination, medical history and testing.

Signs and symptoms

Although different types of anaemias have different causes, the signs and symptoms can be very similar. Mild or moderate forms of anaemia may cause few, if any, symptoms. The most common symptoms are:

  • a general feeling of tiredness or weakness (fatigue)
  • lack of energy


Other signs and symptoms that may develop as the anaemia becomes more severe include headache, dizziness, feeling of cold or numbness in hands and/or feet, pale complexion, shortness of breath, fast or irregular heartbeat and chest pain.

Tests and treatment

Full blood count (FBC)
Anaemia may first be detected when a full blood count (FBC) is done during a health examination or as part of testing for other conditions. A FBC is often ordered as part of a yearly physical examination/check up. It is a routine test that counts the number and relative proportion of each of the different types of cells in your blood stream. It gives your doctor information about the size, shape and relative maturity of the blood cells present in your blood at that moment.


Blood film examination and differential - WBC
If results of the FBC indicate anaemia, it may be followed up with an examination of a blood film or a differential. Results from these tests may give clues as to the cause. Several other tests may be run to help determine the cause of the anaemia and to guide treatment. See the individual discussions of the different types of anaemia for more on these.

Last Updated: Thursday, 1st June 2023

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