Iron deficiency anaemia

Definition

Iron deficiency anaemia (IDA) is a hypochromic, microcytic anaemia caused by inadequate iron availability for haemoglobin synthesis. It results from insufficient dietary intake, impaired absorption, increased requirements, or chronic blood loss.

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Epidemiology

• Most common nutritional deficiency worldwide.

• High prevalence among women of reproductive age, pregnant women, infants, and individuals with chronic gastrointestinal blood loss.

• Accounts for a significant proportion of anaemia cases globally.

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Iron Physiology and Pathophysiology

Iron is essential for haemoglobin production, myoglobin, and various enzymes. The body contains about 3–4 g of iron, mostly in haemoglobin. There is no regulated excretory pathway for iron; balance depends on absorption and loss.

Pathogenesis in IDA:

1. Negative iron balance – depletion of iron stores (low ferritin).

2. Iron-deficient erythropoiesis – insufficient iron supply to bone marrow.

3. Iron deficiency anaemia – reduced haemoglobin synthesis, leading to microcytic, hypochromic red cells.

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Causes

1. Increased Iron Loss

• Gastrointestinal bleeding (peptic ulcer, colorectal cancer, haemorrhoids).

• Menorrhagia.

• Frequent blood donation.

2. Increased Iron Requirements

• Pregnancy, lactation.

• Growth spurts in children and adolescents.

3. Decreased Iron Intake

• Poor dietary iron intake (e.g., vegetarian diets lacking heme iron).

4. Impaired Iron Absorption

• Coeliac disease, inflammatory bowel disease.

• Post-gastrectomy or bariatric surgery.

• Chronic use of proton pump inhibitors (PPIs).

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Clinical Features

General Symptoms (due to anaemia)

• Fatigue, weakness.

• Dyspnoea on exertion.

• Palpitations.

• Headache, dizziness.

Iron-Specific Symptoms

• Pica (craving non-food substances such as ice, dirt).

• Glossitis, angular cheilitis.

• Brittle nails, koilonychia (spoon nails).

• Hair loss.

• Restless legs syndrome (sometimes associated).

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Signs

• Pallor (skin, conjunctivae).

• Tachycardia.

• Systolic flow murmur in severe cases.

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Investigations

Full blood count:

• Microcytosis (low mean corpuscular volume – MCV).

• Hypochromia (low mean corpuscular haemoglobin – MCH).

Iron studies:

• Low serum ferritin – most specific marker of iron deficiency.

• Low serum iron.

• High total iron-binding capacity (TIBC).

• Low transferrin saturation.

Additional tests to identify cause:

• Stool occult blood test.

• Coeliac serology.

• Endoscopy/colonoscopy if GI blood loss suspected.

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Treatment

1. Treat Underlying Cause

• Stop bleeding source (e.g., treat peptic ulcer, manage menorrhagia).

• Address malabsorption causes.

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2. Iron Replacement Therapy

Oral Iron (first-line)

• Ferrous sulfate – 100–200 mg elemental iron daily in divided doses. Common regimen: 325 mg tablet (containing ~65 mg elemental iron) orally twice daily.

• Ferrous fumarate – 300 mg tablet (~100 mg elemental iron) orally once or twice daily.

• Ferrous gluconate – 300 mg tablet (~35 mg elemental iron) orally two to three times daily.

Administration tips:

• Take on an empty stomach for optimal absorption.

• Vitamin C (250–500 mg) enhances absorption.

• Avoid concomitant tea, coffee, dairy, or antacids within 2 hours.

Duration: Continue for 3–6 months after normalisation of haemoglobin to replenish stores.

Side effects: GI upset, constipation, diarrhoea, dark stools.

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Parenteral Iron

Indicated if oral iron is not tolerated, ineffective, or rapid replacement is needed (e.g., severe anaemia before surgery).

• Ferric carboxymaltose – up to 1000 mg IV in a single infusion, repeat if required after at least 1 week.

• Iron sucrose – 200 mg IV over 30 minutes, 2–3 times per week until total dose reached.

• Iron dextran – total dose infusion, dose calculated based on weight and haemoglobin deficit.

Precautions:

• Monitor for hypersensitivity reactions.

• Facilities for resuscitation must be available.

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3. Blood Transfusion

• Reserved for severe symptomatic anaemia or haemodynamic instability.

• One unit of packed red cells increases Hb by ~1 g/dL.

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Prevention

• Adequate dietary intake of iron-rich foods (red meat, poultry, fish, legumes, leafy greens).

• Iron supplementation in high-risk groups (pregnant women – 30–60 mg elemental iron daily).

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Prognosis

• Good if cause is corrected and stores are replenished.

• Recurrence likely if underlying cause persists.