Iron deficiency anaemia
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Background
Iron deficiency anaemia (IDA) is the most common cause of microcytic anaemia worldwide, and the most common cause of any anaemia overall. It occurs when iron availability is insufficient to meet the demands of haemoglobin synthesis.Causes
Excessive loss:- Gastrointestinal bleeding: peptic ulcer, malignancy, angiodysplasia, haemorrhoids. GI blood loss is the most common cause in adult men and postmenopausal women.
- Menorrhagia: most common cause in premenopausal women.
- Hookworm, schistosomiasis and other infestations in tropical countries.
- Rare in the UK, but may occur in children, elderly people, or those with restrictive diets (e.g. vegan/vegetarian without supplementation).
- Pregnancy, lactation, menstruation.
- Periods of rapid growth in children/adolescents.
- Exfoliative skin disease.
- Coeliac disease, inflammatory bowel disease, gastritis, partial/total gastrectomy.
- Drugs such as tetracyclines, quinolones, antacids, and proton pump inhibitors.
Clinical Features
General features of anaemia:
- Fatigue
- Pallor
- Shortness of breath
- Palpitations.
- Koilonychia (spoon-shaped nails).
- Angular cheilitis.
- Atrophic glossitis (smooth, sore tongue).
- Pica (craving for non-nutritive substances).
- Hair thinning.
Laboratory Findings
- Hypochromic, microcytic anaemia on full blood count.
- Blood film: hypochromic/microcytic cells, anisocytosis, poikilocytosis, target cells, pencil cells.
- Abnormal iron studies (see box below)
Iron studies in iron deficiency anaemia
Interpretation of iron studies
Ferritin reflects iron stores but is an acute phase reactant; it may be normal or raised in infection, inflammation, or malignancy despite iron deficiency.
Serum iron is variable and unreliable in isolation.
Transferrin rises in iron deficiency but may fall in chronic inflammation or liver disease; it may rise in women taking the oral contraceptive pill.
Transferrin saturation combines serum iron and transferrin; values <20% support iron deficiency.
- ↓ Serum ferritin (diagnostic if <15 µg/L; <30 µg/L suggestive, especially in children and pregnancy).
- ↓ Serum iron.
- ↑ Transferrin (unless suppressed by chronic inflammation or liver disease).
- ↑ Total iron binding capacity (TIBC).
- ↓ Transferrin saturation (<20% suggests iron depletion).
Interpretation of iron studies
Ferritin reflects iron stores but is an acute phase reactant; it may be normal or raised in infection, inflammation, or malignancy despite iron deficiency.
Serum iron is variable and unreliable in isolation.
Transferrin rises in iron deficiency but may fall in chronic inflammation or liver disease; it may rise in women taking the oral contraceptive pill.
Transferrin saturation combines serum iron and transferrin; values <20% support iron deficiency.
Investigation of Cause
- History and examination should focus on dietary factors, menstrual history, and GI symptoms.
- All men and postmenopausal women with IDA should be investigated for gastrointestinal malignancy (urgent endoscopy/colonoscopy as per 2-week wait pathways in the UK).
- Consider screening for coeliac disease in all patients with unexplained IDA.
Management
Oral iron supplementation:
- First line: ferrous sulfate once daily (65 mg elemental iron). Once-daily dosing is effective and better tolerated than multiple daily doses.
- Alternatives: ferrous fumarate, ferrous gluconate, or liquid preparations if intolerance occurs.
- Hb should rise by approximately 20 g/L within 3–4 weeks of adequate therapy.
- Continue treatment for at least 3 months after Hb normalises to replenish stores.
- Advise to take iron on an empty stomach with water or vitamin C, avoid tea/coffee/calcium around dosing.
- Consider if oral iron is ineffective, poorly tolerated, malabsorption is present, or rapid correction is required (e.g. late pregnancy, severe symptomatic anaemia).
- Reserved for severe, symptomatic anaemia causing cardiovascular compromise. Always follow with iron replacement.
Special Groups
Pregnancy:
- Screen Hb at booking and 28 weeks.
- Anaemia thresholds: <110 g/L (first trimester), <105 g/L (second/third trimester), <100 g/L (postpartum).
- Oral iron is first line; IV iron if poorly tolerated/absorbed or urgent correction required.
- Increased risk during periods of growth.
- Evaluate diet, consider supplementation, and investigate underlying causes.