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Iron deficiency anemia

Last updated: January 13, 2021


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: [3]
    • Children up to 5 years of age
    • 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 [1][4]

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

Based on underlying mechanism [4][6][7]


Clinical features

DICEd Plumm - Dysphagia, Iron deficiency anemia, Carcinoma of the esophagus, Esophageal webs in Plummer-Vinson syndrome.




Laboratory tests [12]

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][12]



Differential diagnoses

See "Diagnostics" in “Anemia.”

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

  • Epidemiology
    • > 40% of pregnant women are iron deficient [18]
    • Second most common cause of anemia in pregnant women (after physiologic anemia)
  • Etiology: increased iron requirements
  • Treatment: oral or IV iron supplementation (see “Treatment” above) [19][20]
  • Complications
    • Increased risk of adverse pregnancy outcomes
    • Impaired fetal neurodevelopment


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