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Iron Deficiency Anemia (IDA)

Iron Deficiency Anemia (IDA) is the most common nutritional deficiency and the most common cause of anemia worldwide. It develops when iron stores become insufficient to support normal hemoglobin synthesis, resulting in reduced oxygen-carrying capacity of the blood.

Also called

Hypochromic Microcytic Anemia (descriptive term)

ICD-10

D50.9

Specialty

Hematology

Onset

Chronic

Reviewed

August 2026

On This Page

Overview

Iron Deficiency Anemia (IDA) occurs when iron availability is insufficient for hemoglobin production. The main causes are chronic blood loss, inadequate dietary intake, increased physiological requirements, and impaired iron absorption. It typically produces a microcytic, hypochromic anemia with low ferritin and low serum iron.

In adults, particularly men and postmenopausal women, Iron Deficiency Anemia (IDA) should be considered a potential sign of occult gastrointestinal blood loss until proven otherwise.

Etiology & Risk Factors

Etiology & Risk Factors

Aetiology

1. Chronic Blood Loss

  • Gastrointestinal bleeding

  • Peptic ulcer disease

  • Gastric or colorectal cancer

  • Inflammatory bowel disease

  • Hemorrhoids

  • Gastrointestinal polyps

  • Menorrhagia

  • Recurrent epistaxis

  • Frequent blood donation

2. Increased Iron Requirements

  • Pregnancy

  • Infancy

  • Childhood

  • Adolescence

3. Reduced Iron Intake

  • Poor dietary intake

  • Malnutrition

  • Restrictive diets

4. Impaired Iron Absorption

  • Celiac disease

  • Atrophic gastritis

  • H. pylori infection

  • Previous gastric or bariatric surgery

  • Inflammatory bowel disease

  • Long-term acid suppression

Risk Factors

  • Menstruation

  • Pregnancy

  • Older age

  • Vegetarian or vegan diet

  • Chronic gastrointestinal disease

  • Previous gastrointestinal surgery

  • Chronic NSAID use

  • Gastrointestinal malignancy

  • Frequent blood donation

Pathophysiology

Reduced iron intake, increased iron requirements, chronic blood loss, or impaired absorption → depletion of iron stores → decreased serum ferritin → reduced iron availability for erythropoiesis → decreased hemoglobin synthesis → production of smaller and paler red blood cells → microcytic hypochromic anemia → reduced oxygen delivery to tissues → compensatory increase in cardiac output → symptoms of anemia and tissue hypoxia.

Clinical Presentation

-Symptoms

  • Fatigue

  • Weakness

  • Reduced exercise tolerance

  • Shortness of breath on exertion

  • Dizziness

  • Headache

  • Palpitations

  • Poor concentration

  • Irritability

-Signs

  • Pallor

  • Tachycardia

  • Brittle nails

  • Koilonychia (spoon-shaped nails)

  • Glossitis

  • Angular cheilitis

  • Hair loss

-Specific Features of Iron Deficiency

    • Pica

    • Pagophagia (ice craving)

    • Restless legs syndrome

History Taking

-Ask about:

  • Fatigue and weakness
  • Shortness of breath
  • Dizziness
  • Palpitations
  • Dietary intake
  • Menstrual history
  • Pregnancy
  • Gastrointestinal symptoms
  • Melena
  • Hematochezia
  • Abdominal pain
  • Change in bowel habits
  • Weight loss
  • Dysphagia
  • NSAID use

Physical Examination

  • General Examination

    Look for:

    • Pallor

    • Tachycardia

    • Signs of heart failure in severe cases

    • Weight loss

    • General nutritional status

    Specific Examination

    Assess for:

    • Koilonychia

    • Glossitis

    • Angular cheilitis

    • Brittle hair

    • Hair loss

    • Lymphadenopathy

    Abdominal Examination

    Look for:

    • Abdominal masses

    • Hepatosplenomegaly

    • Abdominal tenderness

    Rectal Examination

    Consider when gastrointestinal bleeding or colorectal pathology is suspected.

Investigations

  • Complete Blood Count (CBC)

    Typical findings:

    • Low hemoglobin

    • Low hematocrit

    • Low MCV

    • Low MCH

    • Low MCHC

    • Increased RDW

    Iron Studies

    Serum Ferritin

    • Low ferritin is the most specific laboratory finding for iron deficiency.

    Ferritin may be falsely normal or elevated in inflammation because it is an acute-phase reactant.

    Serum Iron

    • Low

    Total Iron-Binding Capacity (TIBC)

    • Increased

    Transferrin Saturation

    • Reduced

    Peripheral Blood Film

    May show:

    • Microcytosis

    • Hypochromia

    • Anisocytosis

    • Poikilocytosis

    • Pencil cells

    Reticulocyte Count

    • Usually low or inappropriately normal before treatment

    • Increases after effective iron replacement

    Additional Investigations to Identify the Cause

    Depending on age, sex, and clinical presentation:

    • Stool testing for occult blood

    • Upper gastrointestinal endoscopy

    • Colonoscopy

    • Celiac disease screening

    • H. pylori testing

    • Gynecological evaluation in women with abnormal uterine bleeding

    • Urinalysis for urinary blood loss

Diagnosis

Diagnosis is based on:

  • Low hemoglobin
  • Microcytic or sometimes initially normocytic anemia
  • Low ferritin
  • Low serum iron
  • Increased TIBC
  • Low transferrin saturation
  • Clinical evidence of iron deficiency

The underlying cause must always be investigated.

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Management

1. Treat the Underlying Cause

  • Control gastrointestinal bleeding

  • Treat peptic ulcer disease

  • Treat H. pylori infection

  • Treat celiac disease

  • Manage heavy menstrual bleeding

  • Treat gastrointestinal malignancy if present

  • Stop or modify offending medications when appropriate

2. Oral Iron Therapy

First-line treatment for most patients:

  • Oral ferrous sulfate

  • Ferrous fumarate

  • Ferrous gluconate

Treatment may be given once daily or on alternate days depending on tolerance and clinical circumstances.

Common adverse effects:

  • Nausea

  • Constipation

  • Abdominal discomfort

  • Dark stools

3. Intravenous Iron

Consider when:

  • Oral iron is not tolerated

  • Oral iron is ineffective

  • Malabsorption is present

  • Significant ongoing blood loss exists

  • Rapid iron replacement is needed

  • Chronic kidney disease or inflammatory conditions limit response

4. Blood Transfusion

Reserved for:

  • Severe symptomatic anemia

  • Hemodynamic instability

  • Active major bleeding

  • Severe tissue hypoxia

Monitoring

  • Monitor hemoglobin response

  • Check reticulocyte response when appropriate

  • Repeat iron studies after treatment

  • Continue iron therapy after hemoglobin normalization to replenish iron stores

Complications

  • Severe fatigue
  • Reduced exercise capacity
  • Cognitive impairment
  • Poor school or work performance
  • Restless legs syndrome
  • Cardiovascular strain
  • Heart failure in severe prolonged cases
  • Pregnancy complications
  • Increased susceptibility to complications from the underlying cause

Prognosis

The prognosis of Iron Deficiency Anemia (IDA) is generally excellent when the underlying cause is identified and treated. Hemoglobin usually improves with adequate iron replacement, but replenishment of total body iron stores takes longer. Persistent or recurrent Iron Deficiency Anemia (IDA) requires reassessment for ongoing blood loss, malabsorption, poor adherence, or an incorrect diagnosis.

Key Points / Clinical Pearls

  • Iron Deficiency Anemia (IDA) is the most common cause of anemia worldwide.
  • The main causes are chronic blood loss, increased requirements, poor intake, and malabsorption.
  • It is typically a microcytic, hypochromic anemia.
  • Low ferritin is the key laboratory marker of depleted iron stores.
  • Serum iron is low and TIBC is usually increased.
    In adult men and postmenopausal women, investigate for occult gastrointestinal blood loss.
  • Oral iron is first-line for most patients.
    IV iron is useful when oral iron is ineffective, poorly tolerated, or contraindicated.
  • Blood transfusion is reserved for severe symptomatic anemia or significant instability.
  • Always identify and treat the underlying cause of Iron Deficiency Anemia (IDA).