Iron deficiency anemia

Last updated: November 29, 2023

Summarytoggle arrow icon

Iron deficiency anemia (IDA) is the most common form of anemia worldwide and is caused by 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 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. Routine screening is only recommended for certain groups. IDA typically manifests as hypochromic, microcytic anemia, but it may also be normocytic. If diagnostic confirmation is needed, a low ferritin level indicates an iron deficiency, but additional iron studies may be necessary. Once IDA is confirmed, the underlying cause must be determined. In adults, this typically involves a gastroscopy and colonoscopy or, in women with abnormal uterine bleeding, a gynecologic workup. In children, a thorough history and review of symptoms, including a comprehensive dietary history, can help direct any further diagnostic evaluation. Patients with anemia severe enough to cause cardiopulmonary instability, or pregnant patients with a Hb < 6 g/dL, require blood transfusions. All other patients can be managed with oral or parenteral iron supplementation.

See also “Anemia.”

Epidemiologytoggle arrow icon

Epidemiological data refers to the US, unless otherwise specified.

Etiologytoggle arrow icon

Based on age [1][4]

The most common causes of IDA in different age groups include:

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

Based on underlying mechanism [4][5][6]

Iron losses

Decreased iron intake

Decreased iron absorption

Increased demand

Pathophysiologytoggle arrow icon

Clinical featurestoggle arrow icon

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


Screeningtoggle arrow icon

Indications [1][11]

  • Recommendations for screening vary between medical bodies. [1][11][12][13][14]
  • Consider screening in the following circumstances:

Method [11]

Recommended intervals [11]

Screening for IDA is not recommended in asymptomatic men and postmenopausal women if they have no risk factors. [1]

Diagnosticstoggle arrow icon


  • Initial investigations
  • Empiric iron therapy can be initiated if:
    • The patient's history points to a clear explanation for IDA (e.g., history of multiple blood donations or inadequate nutritional iron intake)
    • No pathology is found in a young, otherwise healthy patient after the initial investigations
  • Advanced studies (e.g., capsule endoscopy, angiographic or scintigraphic studies): Consider in older symptomatic patients with negative initial workup and no response to empiric iron therapy. [16]

Routine studies [1][16][17]

Diagnosis of iron deficiency [1][4][17][22]

In combination with an elevated TIBC, low ferritin and iron levels 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][22]

Evaluation for underlying causes of iron deficiency [16][22]
Suspected etiology Indications Studies
Gastrointestinal pathologies
  • Origin from or recent travel to resource-limited subtropical or tropical area
  • Eosinophilia on CBC
Gynecologic pathologies
Renal pathologies
Pulmonary pathologies
  • Iron-staining of sputum sample
  • Chest imaging as appropriate

Treatmenttoggle arrow icon

Treatment of the underlying condition

Examples include:

Dietary modifications for IDA

Iron therapy

Oral iron therapy is effective, inexpensive, and is typically the initial treatment for most patients with IDA. Parenteral iron therapy is beneficial in certain cases.

Iron therapy for iron deficiency anemia
Oral iron therapy Parenteral iron therapy [1][17]
  • Individuals with asymptomatic IDA who do not have indications for parenteral iron therapy
Dosage and administration [17]
  • Dosage is based on elemental iron equivalents.
    • Children and adolescents: 3–6 mg/kg/day elemental iron (see “IDA in children and adolescents”) [12][25]
    • Nonpregnant adults
      • Historically, 100–200 mg/day elemental iron in divided doses [4]
      • Newer evidence supports lower doses given less frequently. [17]
    • Pregnant individuals: 60–120 mg/day elemental iron (see “IDA in pregnancy”) [13][14]
  • Common agents include:
    • Ferrous sulfate [17]
    • Ferrous fumarate [17]
    • Ferrous gluconate [17]
  • Enhance absorption of oral iron by giving it: [17][25]
  • Use the Ganzoni formula to calculate the total iron deficit for IV iron dosing.
  • Common agents include:
  • Administer in one or several sittings until the calculated iron deficit is replaced. [17]
Adverse effects [1][28]

Blood transfusion [30][31]

See “Transfusion” for further information.

Ongoing management of IDA [1][4]

  • Obtain monitoring studies to assess response to treatment. [1][17]
    • Check CBC:
      • Monthly until in normal range
      • Then every 3 months for one year
      • Then repeat once after another year
    • Adequate response: After one month, hemoglobin should have increased by ≥ 1 g/dL.
    • Reticulocyte count may also be used for monitoring. [21]
  • Patients receiving oral iron therapy: Continue treatment for 3–6 months to replenish iron stores. [1][4][17]

Differential diagnosestoggle arrow icon

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.

Complicationstoggle arrow icon

We list the most important complications. The selection is not exhaustive.

Preventiontoggle arrow icon

See also “Special patient groups” for additional recommendations for children and pregnant individuals.

Recommended daily dietary intake of iron [11][33]

Recommended daily iron intake [34]
Age Male individuals Female individuals
≤ 6 months
  • 0.27 mg [34][35]
7–12 months
  • 11 mg
1–3 years
  • 7 mg
4–8 years
  • 10 mg
9–13 years
  • 8 mg
14–18 years
  • 11 mg
  • 15 mg
19–50 years
  • 8 mg
≥ 51 years

The National Academy of Medicine (formerly known as the Institute of Medicine) recommends that vegetarians consume almost twice the recommended daily dietary intake of iron because nonheme iron is not as easily absorbed as heme iron. [37]

Special patient groupstoggle arrow icon

Certain patient groups are at increased risk of both developing IDA and complications resulting from it.

Iron deficiency anemia in children and adolescentstoggle arrow icon

Rapid periods of growth increase the body's demand for iron, putting children and infants at risk of anemia. Children who develop anemia have a higher risk of developmental delay and infections. [4]

Risk factors for pediatric IDA [11][25][26]

IDA is a risk factor for pediatric lead toxicity. [25]

Cow's milk has a very low concentration of iron and also disrupts iron absorption. [39]

Clinical features

Screening [12]

  • Guidelines on screening children for IDA vary regarding which children to screen and the frequency of screening.
  • Screen children with risk factors for pediatric IDA at set intervals. [12][26][41]
  • Consider screening all infants at the 12-month well-child visit. [12]
  • Method [26]
  • Next steps: If anemia is present, verify capillary samples with venous samples and proceed to diagnostics studies.

Diagnostics [12][26]

In children with mild microcytic or normocytic anemia and a history of poor dietary iron intake, IDA can be presumed and empirically treated. The diagnosis can be confirmed with either a 1 g/dL increase in hemoglobin concentration after 1 month of iron therapy or with confirmatory testing for IDA. [26]

Management [1][4][25]

Prevention of IDA in children [11][25]

Do not introduce low-iron milk (e.g., cow's milk) before 12 months of age. [26]

Do not routinely start iron prophylaxis in children who receive frequent blood transfusions, because of the risk of iron overload. [26]

Iron deficiency anemia in pregnancytoggle arrow icon

Iron deficiency anemia in pregnancy is associated with preterm labor, low birth weight, and increased mortality for both the mother and neonate. Diagnostic Hb levels for anemia during pregnancy should be used when assessing for IDA as there is an expected physiological decrease in hemoglobin during pregnancy because of increased plasma volume (known as dilutional anemia). [4][13]


  • 30–50% of pregnant individuals worldwide have an iron deficiency. [29][47]
  • IDA is the most common type of anemia during pregnancy. [29]


  • Increased fetal iron requirements for RBC production and fetoplacental growth
  • Increased RBC mass [48]
  • See also “Etiology of IDA.”

Clinical features

  • Clinical features of IDA do not significantly differ in pregnant individuals.
  • For effects on the fetus, see “Complications” below.

Screening for IDA in pregnancy [11][13][14][14][49]

Diagnostics [4][13]

In pregnant individuals with nonsevere microcytic or normocytic anemia and nothing to suggest an alternative cause of anemia, IDA can be presumed and empirically treated. The diagnosis is confirmed with an appropriate increase in hemoglobin concentration within 2–4 weeks of initiating iron therapy or with confirmatory testing for IDA. [1][13][50]

Management [11][13][45]

Complications [4]

Prevention [13][14]

  • Encourage patients to consume the recommended daily dietary intake of iron (i.e., 27 mg). [11][13]
  • Consider routine supplementation with low-dose iron (i.e., 27 mg/day) starting at the first prenatal visit. [11][13][14]

Avoid iron supplements in pregnant individuals with conditions that increase iron levels in the body (e.g., hemochromatosis) without first consulting the patient's hematologist. [13]

Referencestoggle arrow icon

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