Key Facts

Iron deficiency anaemia (IDA) is the most common cause of anaemia worldwide. It is characterised by reduced haemoglobin synthesis due to inadequate iron stores.

Epidemiology

• Global: ~2 billion affected; most common nutritional deficiency
• UK: ~3% of men, ~8% of non-pregnant women, ~20% of pregnant women
• Most common cause of microcytic anaemia

Aetiology

• Blood loss (most common in developed countries):
  • Premenopausal women: menorrhagia (most common cause)
  • Males/postmenopausal: GI tract (peptic ulcer, NSAIDs, colorectal cancer, oesophageal/gastric cancer)
• Reduced absorption: coeliac disease, gastrectomy, H. pylori, PPIs
• Increased demand: pregnancy, growth (children/adolescents)
• Dietary insufficiency: vegans/vegetarians, elderly, children

Pathophysiology

• Iron is essential for haem synthesis in erythropoiesis
• Total body iron ~3–4g; ~70% in haemoglobin
• Iron absorbed in duodenum/proximal jejunum
• Hepcidin (liver): master regulator — reduces iron absorption and release from macrophages in iron-replete state
• Iron deficiency: reduced Hb synthesis → microcytic hypochromic RBCs
• Stages: iron depletion (low ferritin, normal Hb) → iron-deficient erythropoiesis (low transferrin saturation) → IDA (low Hb)

General Anaemia Symptoms

• Fatigue, lethargy, weakness
• Dyspnoea on exertion, palpitations
• Pallor (conjunctivae, palmar creases)
• Dizziness, headache

Specific to Iron Deficiency

• Koilonychia: spoon-shaped nails
• Angular stomatitis/cheilitis: painful cracks at mouth corners
• Glossitis: smooth, red, painful tongue
• Pica: craving non-food substances (ice — pagophagia, soil, chalk)
• Restless legs syndrome
• Plummer-Vinson/Paterson-Brown-Kelly syndrome: IDA + post-cricoid web + dysphagia

Red Flags

• IDA in male or postmenopausal female (GI malignancy until proven otherwise)
• Rectal bleeding, change in bowel habit, weight loss
• Dysphagia
• Failure to respond to oral iron (malabsorption, ongoing blood loss, wrong diagnosis)

Bloods

• FBC: low Hb, low MCV (<80 fL), low MCH, ± thrombocytosis (reactive)
• Iron studies:
  • Ferritin: LOW (<15 µg/L diagnostic; <30 µg/L with anaemia significant) — best single test
  • Serum iron: low
  • TIBC/transferrin: raised
  • Transferrin saturation: low (<20%)
• Blood film: microcytic hypochromic RBCs, target cells, pencil cells
• Reticulocyte count: low (inappropriate for degree of anaemia)
• Anti-tTG/EMA: screen for coeliac disease in ALL IDA
• CRP: to interpret ferritin (acute phase reactant)

GI Investigation (males and postmenopausal females with IDA)

• BSG guidelines: upper AND lower GI investigation
  • Gastroscopy: peptic ulcer, gastric/oesophageal cancer, coeliac biopsies
  • Colonoscopy: colorectal cancer, polyps, angiodysplasia
  • If both normal: consider small bowel investigation (capsule endoscopy)

Special Tests

• Hb electrophoresis: if thalassaemia suspected
• H. pylori testing: if gastroscopy performed
• Faecal calprotectin: IBD screen if symptoms suggest

Pharmacological

Oral iron (first-line):

• Ferrous sulphate 200mg TDS (65mg elemental iron/tablet) — most commonly prescribed
• Ferrous fumarate 210mg TDS: alternative (higher elemental iron: 68mg/tablet)
• Ferrous gluconate 300mg TDS: better tolerated but lower elemental iron (35mg/tablet)
• Take on empty stomach with vitamin C (orange juice) to enhance absorption
• Avoid taking with tea, coffee, calcium, PPIs (reduce absorption)

Duration:

• Continue for 3 months after Hb normalises to replenish iron stores
• Check Hb at 2–4 weeks (should rise ~10–20 g/L per month)

IV iron (if oral intolerant, non-responsive, or rapid correction needed):

• Ferric carboxymaltose (Ferinject) 1g IV: single infusion; well-tolerated
• Iron sucrose 200mg IV: may need multiple doses
• Indications: oral intolerance, malabsorption, CKD on dialysis, perioperative, IBD, pregnancy (2nd/3rd trimester if oral failed)

Non-pharmacological

• Dietary advice: red meat, green vegetables, fortified cereals
• Treat underlying cause (menorrhagia, GI pathology, coeliac)

Referral Criteria

• Urgent 2-week-wait referral: IDA in male/postmenopausal female (BSG: upper + lower GI investigation)
• Gastroenterology: failure to respond to iron, recurrent IDA, coeliac disease
• Gynaecology: menorrhagia management
• Haematology: if alternative diagnosis suspected

• Excellent with appropriate treatment and cause identification
• Oral iron: Hb normalises within 6–8 weeks; stores replenished by 3–6 months
• Failure to respond to oral iron (4–6 weeks): consider non-compliance, ongoing blood loss, malabsorption, wrong diagnosis
• Iron deficiency without anaemia: treat to prevent progression and improve symptoms (fatigue, RLS)
• Colorectal cancer presents as IDA in ~10–15% of cases — early detection crucial

Iron Studies Interpretation