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Anemia, Iron Deficiency (IDA)

Description:
- Low serum iron with low hemoglobin (Hgb) or microcytic, hypochromic RBCs.
- Anemia defined as Hgb 2 standard deviations below normal for age and sex (1).
- Onset: acute (rapid blood loss) or chronic (slow blood loss, poor intake, poor absorption).
- Causes blood oxygen deficiency impacting hematologic, lymphatic, immunologic, cardiac, GI systems.

Epidemiology

  • Most common nutritional deficiency worldwide; IDA most common cause of anemia (~50%).
  • Affects all ages; toddlers, menstruating and pregnant women at higher risk.
  • Females predominate.
  • Incidence: men 2%, women 15-20% annually; infants/toddlers 3-5%; pregnant patients up to 20% (1).
  • Prevalence: 2 billion worldwide; infants/children <12 years: 4-7%; menstruating women: 30%.

Etiology and Pathophysiology

  • Depletion of iron stores → decreased reticulocyte count & Hgb production.
  • Causes:
  • Blood loss (menses, GI bleeding, trauma)
  • Poor iron intake
  • Poor absorption (atrophic gastritis, postgastrectomy, celiac disease)
  • Increased demand (infancy, adolescence, pregnancy, breastfeeding)

Risk Factors

  • Premenopausal women
  • Frequent blood donors
  • Pregnancy/lactation, young maternal age
  • Strict vegan diet
  • NSAID use
  • Frequent blood draws in hospital
  • Residence/travel in hookworm endemic areas

General Prevention

  • Screening asymptomatic pregnant women & high-risk children (varies by guideline) (1)[C].
  • Supplementation for at-risk infants 6-12 months (1),(2).
  • Iron and vitamin C rich diet for menstruating women.
  • Iron 30 mg/day for asymptomatic pregnant women (2).

Commonly Associated Conditions

  • GI malignancy, PUD, Helicobacter pylori infection
  • Irritable bowel disease (IBD)
  • Hookworm/parasitic infestation
  • Hypermenorrhagia
  • Pregnancy
  • Gastric bypass surgery (obesity treatment)
  • Malnutrition
  • NSAID or antacid medication use

Diagnosis

History

  • Mostly asymptomatic; severe anemia symptoms: weakness, fatigue, malaise, headache, concentration issues, exertional dyspnea, angina, melena, pica.

Physical Exam

  • Pallor (skin, conjunctiva, sublingual)
  • Tachycardia, tachypnea, cool extremities
  • Brittle nails/hair
  • Signs of heart failure

Differential Diagnosis

  • GI bleeding causes (gastritis, carcinoma, varices, celiac)
  • Chronic intravascular hemolysis
  • Defective iron usage (thalassemia trait, sideroblastosis, G6PD deficiency)
  • Defective iron reutilization (infection, inflammation, hypothyroid, cancer)
  • Hypoproliferation (hypothyroid, renal failure)
  • Other anemias (ACD, thalassemia, lead poisoning)

Diagnostic Tests

  • Labs: Hgb, HCT, ferritin, serum iron, TIBC.
  • Hgb: <13 g/dL men, <12 g/dL women.
  • MCV: <80 fL (may be low normal in mild cases).
  • Ferritin: <15 µg/L diagnostic of IDA; >100 µg/L rules out.
  • Iron studies: low ferritin, serum iron, transferrin saturation; high TIBC, transferrin.
  • RDW increased in mixed deficiencies.
  • Peripheral smear: hypochromia, microcytosis; low reticulocyte production index.
  • Consider G6PD, thalassemia testing if indicated.
  • Celiac serology if suspected.
  • TSH for hypothyroidism.
  • Stool guaiac and ova/parasites testing if at risk.
  • Endoscopy/colonoscopy for GI bleeding in men/postmenopausal women or refractory cases (1)[C].
  • Bone marrow aspiration rarely needed.

Treatment

General Measures

  • Identify and correct underlying cause.
  • Avoid transfusion except in rare/severe cases.

Medications

  • Elemental iron 100-200 mg/day adults; 3-6 mg/kg/day children.
  • Ferrous sulfate, gluconate, fumarate oral formulations; taken on empty stomach 1 hour before meals (1)[C].
  • Vitamin C enhances iron absorption.
  • Acid suppression meds reduce iron absorption.
  • IV iron for intolerance to oral or severe anemia or special cases (pregnancy, malabsorption, heavy bleeding).
  • IV iron formulations: iron dextran, ferumoxytol, ferric carboxymaltose.
  • Iron dose calculation formula provided.
  • Blood transfusion for severe anemia, symptomatic cases (Hgb threshold varies). Pregnant women transfuse if Hgb <6 (1)[C].

Issues for Referral

  • Men/postmenopausal women with IDA (rule out colon cancer).
  • Pregnant women Hgb <9 g/dL.
  • Nonpregnant adults Hgb <6 g/dL.
  • Nonresponse to 4-6 week oral iron trial.

Ongoing Care

Follow-Up

  • Monitor every 3 months after normalization for 1 year, then yearly (1)[C].
  • Expect Hgb rise ~1 g/dL every 3-4 weeks.
  • Iron stores normalize ~4 weeks after Hgb normalizes.

Diet

  • Iron-rich foods: red meat, poultry, fish, eggs (heme iron best absorbed).
  • Non-heme iron sources: lentils, beans, leafy greens, raisins, tofu, fortified cereals.
  • Vitamin C-rich foods improve absorption.
  • Avoid dairy/milk 2 hours before/after iron.
  • Limit milk to 16 oz/day (adults).
  • Limit tea, coffee, caffeine.
  • Increase fluids/fiber to prevent constipation.
  • Avoid phytates, polyphenols.

Patient Education

Prognosis

  • IDA resolves with iron therapy and treatment of underlying cause.
  • Treat hypothyroidism if present to improve response.

Complications

  • Ischemic events and heart failure risk, especially elderly.
  • Poor growth, failure to thrive, developmental delays in children.

References

  1. Short MW, Domagalski JE. Iron deficiency anemia: evaluation and management. Am Fam Physician. 2013;87(2):98-104.
  2. McDonagh M, Cantor A, Bougatsos C, et al. Routine Iron Supplementation and Screening for Iron Deficiency Anemia in Pregnant Women: Systematic Review. AHRQ. 2015.

Additional Reading

See Also

  • Algorithm: Anemia

ICD10 Codes

  • D50.9 Iron deficiency anemia, unspecified
  • D50 Iron deficiency anemia
  • O99.01 Anemia complicating pregnancy

Clinical Pearls

  • IDA due to poor dietary iron intake is the most common anemia.
  • Blood loss and malabsorption contribute to iron deficiency.
  • Premenopausal women and children are at highest risk.