Iron Deficiency Anaemia: Causes, Tests and Iron Treatment

Iron deficiency anaemia is the most common type of anaemia worldwide. It is extremely common in Pakistan and South Asia, especially among women, children and pregnant women. In adults it can also be the first sign of serious disease, such as bowel cancer, so finding the cause is as important as treating the anaemia.

Causes

• Blood loss:
  • heavy menstrual bleeding
  • gastrointestinal bleeding (peptic ulcer, NSAIDs, cancer, angiodysplasia, hookworm)
• Increased needs: pregnancy, infancy and adolescence.
• Poor intake: a diet low in iron, or excess tea with meals, which reduces absorption.
• Malabsorption:
  • coeliac disease
  • atrophic gastritis
  • H. pylori
  • after gastric surgery
  • long-term PPIs

Clinical features

Symptoms:

• tiredness
• breathlessness on exertion
• palpitations
• headaches
• poor concentration
• pica (craving non-food items such as ice or clay)

Signs:

• pallor
• koilonychia (spoon-shaped nails)
• angular stomatitis
• glossitis
• brittle hair and nails

In children, iron deficiency affects growth and development.

Investigations

• Full blood count:
  • low haemoglobin
  • microcytic (low MCV)
  • hypochromic (low MCH)
  • often a raised red cell distribution width
• Serum ferritin: a low ferritin confirms iron deficiency. Ferritin rises in inflammation, infection and liver disease, so a "normal" ferritin does not exclude deficiency in these situations. Transferrin saturation helps.
• Blood film: microcytic, hypochromic cells, and pencil cells.
• Find the cause:
  • menstrual and dietary history
  • coeliac serology
  • urine for blood
  • stool examination for parasites where relevant
  • in men and postmenopausal women: upper GI endoscopy and colonoscopy to exclude GI blood loss and cancer, following local guidelines

Iron deficiency versus thalassaemia trait

Both cause microcytosis. In thalassaemia trait:

• the red cell count is often normal or high
• anaemia is mild
• ferritin is normal
• HbA₂ is raised in beta thalassaemia trait

The Mentzer index (MCV divided by red cell count) below about 13 suggests thalassaemia trait. Iron should not be given to thalassaemia patients who are not iron-deficient.

Treatment

• Treat the cause.
• Oral iron (for example ferrous sulfate or ferrous fumarate), usually once daily or on alternate days. This is often better tolerated and absorbed than several doses a day.
  • Take on an empty stomach, or with vitamin C, and away from tea, milk and antacids.
  • Side effects: nausea, constipation and dark stools.
• Check response: haemoglobin should start rising within 2–4 weeks. Continue for about 3 months after haemoglobin normalises, to replenish stores.
• IV iron for intolerance, malabsorption, ongoing losses, late pregnancy or the need for rapid correction.
• Blood transfusion only for severe symptomatic anaemia or haemodynamic instability.

Exam pearls

• Unexplained iron deficiency in a man or postmenopausal woman needs GI investigation.
• Low ferritin is diagnostic. Normal ferritin does not exclude deficiency during inflammation.
• Hookworm infection is an important cause in endemic areas.

See also Thalassaemia, Vitamin B12 and Folate Deficiency and our Clinical Eye Series: Fingernails.

Test yourself

5 exam-style single-best-answer questions. Choose your answer, then tap “Show answer”.

1. Most specific test for iron deficiency:

   1. Haemoglobin
   2. Serum iron
   3. Low serum ferritin
   4. Platelet count
   5. MCV
   Show answer

   Answer: C. Low serum ferritin
   Low ferritin confirms iron deficiency; note ferritin rises in inflammation.

2. A 65-year-old man has unexplained iron deficiency anaemia. Next step?

   1. Repeat in a year
   2. Blood transfusion
   3. Upper GI endoscopy and colonoscopy
   4. Bone marrow biopsy
   5. Oral iron only
   Show answer

   Answer: C. Upper GI endoscopy and colonoscopy
   Exclude GI blood loss and cancer in men and postmenopausal women.

3. Spoon-shaped nails are called:

   1. Leukonychia
   2. Koilonychia
   3. Clubbing
   4. Onycholysis
   5. Beau's lines
   Show answer

   Answer: B. Koilonychia
   Koilonychia is a sign of iron deficiency.

4. Microcytosis, normal ferritin and a high red cell count suggest:

   1. Hypothyroidism
   2. Liver disease
   3. Thalassaemia trait
   4. B12 deficiency
   5. Iron deficiency
   Show answer

   Answer: C. Thalassaemia trait
   Thalassaemia trait gives microcytosis with normal iron stores and a relatively high RBC count.

5. Which drink reduces iron absorption when taken with meals?

   1. Lemon water
   2. Tea
   3. Orange juice
   4. None
   5. Water
   Show answer

   Answer: B. Tea
   Tannins in tea reduce non-haem iron absorption; vitamin C improves it.

More articles in Haematology

• Thalassaemia: Genetics, Diagnosis and Transfusion CareBeta thalassaemia trait, intermedia and major, HbA2 and HPLC, transfusion and iron chelation, complications, screening and prevention.
• Vitamin B12 and Folate Deficiency: Megaloblastic AnaemiaCauses of B12 and folate deficiency, neurological signs, blood film, pernicious anaemia, hydroxocobalamin and why B12 is replaced before folate.

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Disclaimer

For education and exam preparation only. This is not medical advice and must not be used to diagnose or treat patients. Always follow current clinical guidelines and the advice of qualified senior colleagues.