• Clinical science

Iron deficiency anemia


Iron deficiency anemia (IDA) is the most common form of anemia worldwide and can be due to inadequate intake, decreased absorption (e.g., atrophic gastritis, inflammatory bowel disease), increased demand (e.g., during pregnancy), or increased loss (e.g., gastrointestinal bleeding, menorrhagia) of iron. Prolonged deficiency depletes the iron stores in the body, resulting in decreased erythropoiesis and anemia. Symptoms are nonspecific and include fatigue, pallor, lethargy, hair loss, brittle nails, and pica. Diagnostic lab values include low hemoglobin, microcytic, hypochromic red blood cells on peripheral smear, and low ferritin and iron levels. Once diagnosed, the underlying cause should be determined. Patients at risk for underlying gastrointestinal malignancy should also undergo a colonoscopy. Iron deficiency anemia is treated with oral (most common) or parenteral iron supplementation. Severe anemia or those with concomitant cardiac conditions may also require blood transfusions. The underlying cause of IDA should also be corrected.


  • Most common form of anemia worldwide [1]
  • ∼ 3% of the general population in the United States is affected [2]
  • Ethnic variations: African-American and Mexican-American populations in the US are at increased risk.
  • Prevalence highest in:
    • Children ages 0–5 years
    • Young women of child-bearing age (due to menstrual blood loss)
    • Pregnant women


Epidemiological data refers to the US, unless otherwise specified.


The most common causes of IDA can be divided by age groups and pathophysiologic mechanisms.

Based on age [6][1]

In developed countries, adults > 50 years that present with IDA should have colon polyps/carcinoma ruled out as a potential underlying etiology!

Based on underlying mechanism [6]



Clinical features



Laboratory tests

Low ferritin and iron levels in combination with an elevated TIBC are diagnostic of iron deficiency anemia!

Increased ferritin does not rule out iron deficiency anemia. It can be increased in response to simultaneous inflammation!

Evaluation for underlying cause [1]



  • Dietary modifications
    • Infants and young children: restrict cow's milk intake, use iron-fortified formula, introduce iron-rich foods (pureed form)
    • Adults: increase consumption of iron-rich diet (meats, iron-fortified food, fresh green leafy vegetables)
  • Oral iron therapy:
    • Indicated in all patients with IDA (if tolerated)
    • Should initially be administered for 3–6 months [6]
    • Adverse effects: gastrointestinal discomfort, nausea, constipation, black discoloration of stool
    • Absorption may be enhanced by simultaneous consumption of vitamin C (e.g., with lime juice).
    • Foods (e.g., tea, cereals) and drugs (e.g., calcium, antacids, PPIs; ) that decrease intestinal absorption of iron should be avoided.
  • Parenteral iron therapy
  • Blood transfusion
  • Treat the underlying disease (e.g., antihelminthics for hookworm, OCPs for menorrhagia)


Differential diagnoses

See "Diagnostics" in anemia for more information.

Iron deficiency anemia Anemia of chronic disease
Ferritin Normal to
Iron normal to ↓
Transferrin/TIBC Slightly ↓
Transferrin saturation Normal to slightly ↓
RDW normal
Soluble transferrin receptor (sTfR) normal


The differential diagnoses listed here are not exhaustive.

Special patient groups

Iron deficiency anemia in pregnancy [20]

  • Epidemiology
    • > 40% of pregnant women are iron deficient
    • Second most common cause of anemia in pregnant women (after physiologic anemia)
  • Etiology: increased iron requirements
  • Complications
    • Increased risk of adverse pregnancy outcomes
    • Impaired fetal neurodevelopment
  • Treatment: oral iron supplementation (see “Treatment” above)