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.(IDA) is the most common form of
See also “Anemia.”
- Most common form of anemia worldwide 
- ∼ 3% of the general population in the US is affected. 
- African American and Mexican American populations in the US are at increased risk.
- Prevalence is highest in: 
Epidemiological data refers to the US, unless otherwise specified.
Based on age 
The most common causes of IDA in different age groups include:
- Older adults > 50 years
- Adults < 50 years
- Children: See “ .”
Based on underlying mechanism 
- Gastrointestinal bleeding
- Menstruation, particularly for individuals with heavy menstrual bleeding
- Hemorrhagic diathesis (e.g., hemophilia, )
- Meckel diverticulum
- Dialysis-dependent renal failure
- Frequent blood donation
Decreased iron intake
Decreased iron absorption
- Achlorhydria/hypochlorhydria (e.g., due to autoimmune or Helicobacter pylori infection-induced atrophic gastritis)
- Inflammatory bowel disease, celiac disease
- Surgical resection of the duodenum
- Bariatric surgery
- Frequently asymptomatic
- Fatigue, lethargy
- Pallor (primarily seen in highly vascularized mucosa, e.g., the conjunctiva)
- Cardiac: tachycardia, angina, dyspnea on exertion, pedal edema, and cardiomyopathy in severe cases
- Brittle nails, koilonychia (spoon-like nail deformity) , hair loss
- Pica, dysphagia
- Angular cheilitis: inflammation and fissuring of the corners of the mouth 
- Atrophic glossitis: erythematous, edematous, painful tongue with loss of tongue papillae (smooth, bald appearance)
IDA can be associated with Plummer-Vinson syndrome (PVS) 
- Triad of iron deficiency anemia, postcricoid dysphagia, and upper esophageal webs
- Associated with an increased risk of glossitis and
- Etiopathogenesis unknown
- Recommendations for screening vary between medical bodies. 
- Consider screening in the following circumstances:
- Measure capillary or venous Hb level (with a Hb or CBC test).
- Assess whether Hb levels match the .
- In patients with anemia, verify capillary samples with a venous CBC and proceed to .
Recommended intervals 
- Nonpregnant women:
- Pregnant individuals and children: See “Special patient groups.”
- Men with risk factors for IDA or previous IDA: periodically 
- 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. 
Routine studies 
- ↓ Hemoglobin: The WHO definition of anemia is a hemoglobin level less than two standard deviations below the mean (adjusted for age and sex), i.e.: 
- ↓ Hematocrit
- ↑ Platelet count (reactive thrombocytosis) 
Red blood cell indices 
- RBC: initially normal (decreased with prolonged deficiency)
- Mean corpuscular volume
Mean corpuscular hemoglobin
- Typically ↓ (hypochromic)
- May be normal (normochromic)
- Normal or ↓ reticulocyte count
- Peripheral blood smear: : anisocytosis and hypochromasia (increased zone of central pallor) 
Diagnosis of iron deficiency 
- Best initial test: ↓ serum ferritin 
- Further evaluation
- Additional tests to consider
- Serum : elevated
- EPO: normal or elevated 
- Bone marrow biopsy 
Evaluation for underlying cause 
|Evaluation for underlying causes of iron deficiency |
|Gynecologic pathologies|| |
Treatment of the underlying condition
- : e.g., hormonal therapy (OCPs), tranexamic acid, gynecologic surgery
- GI pathology
- Hookworm infection: antihelminthics
- Malnutrition or malabsorption: Identification and treatment of underlying causes (e.g., eating disorders) and nutritional supplementation
Dietary modifications for IDA
- Encourage the consumption of:
- Counsel patients to limit intake of substances that reduce iron absorption. 
|Iron therapy for iron deficiency anemia|
|Oral iron therapy||Parenteral iron therapy |
|Indications|| || |
|Dosage and administration || || |
|Adverse effects |
Blood transfusion 
See “” for further information.
- Consider : in
- Avoid pRBCs in: hemodynamically stable patients with mild or moderate IDA.
Ongoing management of IDA 
- Obtain monitoring studies to assess response to treatment. 
- Patients receiving oral iron therapy: Continue treatment for 3–6 months to replenish iron stores. 
See "Diagnostics" in “.”
- Acute blood loss anemia
- Occult bleeding
- : Serum ferritin levels and transferrin saturation levels are normal or increased.
- (esp. in children)
- co-exist with IDA) (may : Serum ferritin levels and transferrin saturation levels are usually normal.
|Iron deficiency anemia||Anemia of chronic disease|
|Ferritin||↓||Normal to ↑|
|Iron||↓||normal to ↓|
|Transferrin saturation||↓||Normal to slightly ↓|
|Soluble transferrin receptor (sTfR)||↑||normal|
The differential diagnoses listed here are not exhaustive.
See also “Special patient groups” for additional recommendations for children and pregnant individuals.
Recommended daily dietary intake of iron 
- The recommended daily intake of iron is calculated based on age, sex, and, in female individuals, gynecologic history (i.e., menstruation, pregnancy, breastfeeding).
- Most individuals achieve adequate intake through the consumption of iron-rich foods, e.g.:
- Vitamin supplements are indicated in individuals unable to consume the recommended amount of iron-rich foods or who have risk factors for IDA.
|Recommended daily iron intake |
|Age||Male individuals||Female individuals|
|≤ 6 months|| |
|7–12 months|| |
|1–3 years|| |
|4–8 years|| |
|9–13 years|| |
|14–18 years|| || |
|19–50 years|| |
|≥ 51 years|| |
Special patient groups
Certain patient groups are at increased risk of both developing IDA and complications resulting from it.
Risk factors for pediatric IDA 
- Prematurity 
- low birth weight) (i.e.,
- Poor dietary intake of iron-fortified or iron-rich foods, e.g.:
- GI bleeding (e.g., )
- Intellectual disability
- Low socioeconomic status, including living in areas with a high prevalence of IDA
IDA is a ristor for . 
- Clinical features of IDA in children are similar to those in adults.
- Commonly asymptomatic 
- Young children can present with irritability or pica. 
- Children with anemia have an increased risk of infections and developmental delay. 
- Guidelines on screening children for IDA vary regarding which children to screen and the frequency of screening.
- Screen children with at set intervals. 
- Consider screening all infants at the 12-month well-child visit. 
- Method 
- Next steps: If anemia is present, verify capillary samples with venous samples and proceed to diagnostics studies.
- Serum CBC to confirm anemia (according to the WHO definition of anemia).
- < 6 months of age: varies depending on age 
- 6–59 months: < 11 g/dL
- 5–11 years: < 11.5 g/dL
- 12–14 years: < 12.0 g/dL
- , e.g.:  to confirm a (recommended for most patients)
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. 
- Severe anemia
- Mild or moderate anemia: 3–6 mg/kg/day of oral elemental iron 
- See “Treatment for IDA” for more information on:
Prevention of IDA in children 
- All children: Encourage the recommended daily dietary intake of iron. 
- In children with iron supplementation, e.g., in: 
- Term breastfed infants ≥ 4 months of age: 1 mg/kg/day of elemental iron until there is an adequate intake of iron-rich foods (e.g., iron-fortified cereal) 
- Premature breastfed infants: 2 mg/kg/day of elemental iron until 12 months of age 
- Children living in regions with a high prevalence of IDA : Consider oral iron supplementation. 
Do not introduce low-iron milk (e.g., cow's milk) before 12 months of age. 
Iron deficiency anemia in pregnancy is associated with preterm labor, low birth weight, and increased mortality for both the mother and neonate. 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). 
- 30–50% of pregnant individuals worldwide have an iron deficiency. 
- IDA is the most common type of anemia during pregnancy. 
- Increased fetal iron requirements for RBC production and fetoplacental growth
- Increased RBC mass 
- See also “Etiology of IDA.”
- Clinical features of IDA do not significantly differ in pregnant individuals.
- For effects on the fetus, see “Complications” below.
Screening for IDA in pregnancy 
- Recommended screening times: 
- First prenatal visit and again at 24–28 weeks' gestational age
- Consider screening once during each trimester.
- Method: Obtain a CBC to assess for diagnostic Hb levels for anemia during pregnancy.
- Next steps: If anemia is present, proceed to diagnostics.
- Routine studies
- Diagnostic Hb levels for anemia during pregnancy 
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. 
- Severe anemia (< 7 g/dL)
- For asymptomatic mild or moderate anemia (Hb ≥ 7 g/dL): 60–120 mg/day of oral elemental iron 
- See “Treatment for IDA” for more information on:
- Increased risk of adverse maternal/fetal outcomes (e.g., low birth weight, neonatal anemia, premature labor)
- Impaired fetal neurodevelopment
- Encourage patients to consume the recommended daily dietary intake of iron (i.e., 27 mg). 
- Consider routine supplementation with low-dose iron (i.e., 27 mg/day) starting at the first prenatal visit.