- Clinical science
Iron deficiency anemia (IDA) is the most common cause of anemia worldwide and can be due to inadequate intake, decreased absorption (e.g., atrophic gastritis, IBD), increased demand (e.g., during pregnancy), or increased loss (e.g., GI bleeding, menorrhagia). Prolonged deficiency depletes the iron stores in the body, resulting in decreased erythropoiesis and IDA. Symptoms are nonspecific and include fatigue, pallor, lethargy, hair loss, brittle nails, and pica. Some patients may also present with features of cardiac failure (e.g., dyspnea on exertion, pedal edema). Low hemoglobin, microcytic hypochromic blood picture on peripheral smear, and iron studies (↓ ferritin and transferrin saturation, ↑ transferrin levels) are used to diagnose IDA. Once diagnosed, the etiology should be determined. Stool examination for hookworm ova and occult blood are indicated in all patients with IDA. Patients at high risk of underlying GI malignancy (men of all ages/postmenopausal women with IDA) should also undergo colonoscopy and endoscopy. Iron deficiency anemia is treated with oral (most common) or parenteral supplementation of iron. Severe anemia or those with concomitant cardiac conditions may also require blood transfusions. The underlying cause for IDA should also be corrected.
- At-risk groups
Epidemiological data refers to the US, unless otherwise specified.
- Cereal-rich diet
- Chronic undernutrition
- Achlorhydria/hypochlorhydria (e.g., due to autoimmune or H. pylori infection induced atrophic gastritis)
- Inflamed/ulcerated intestinal mucosa: Inflammatory bowel disease, Celiac disease
- Bariatric surgery
- In children: excessive intake of cow's milk (> 24 ounces/700 mL per day)
- In infants: substituting breastfeeding and/or iron-fortified formulas with cow's milk
- Growth spurt
Gastrointestinal bleeding (most common cause in adult males and postmenopausal females)
- Increased risk with NSAID use 
- Hemorrhagic diathesis (e.g., hemophilia, von Willebrand disease)
- Dialysis-dependent renal failure
- Frequent blood donation ♂: > 3 times per year; ♀: > 2 times per year
- Gastrointestinal bleeding (most common cause in adult males and postmenopausal females)
- Iron stores in the body
- Dietary iron
- Occurs in the duodenum and upper jejunum
- Ferric iron (non-heme iron) is reduced to ferrous iron and then absorbed; heme iron is directly absorbed into the intestinal cell.
- The enzyme ceruloplasmin oxidizes ferrous iron back to ferric iron.
- Transferrin (an enzyme synthesized in the liver) binds and transports the ferric iron to the erythroid precursors (in bone marrow) for hemoglobin synthesis.
- Iron recycling
- Iron loss
- Fatigue, lethargy, pallor
- Brittle nails, koilonychia; , hair loss
- Pica , dysphagia
- Chronic/severe IDA may present with cardiac symptoms such as angina, dyspnea on exertion, pedal edema
- Angular cheilitis; , atrophic glossitis
- Plummer-Vinson syndrome (PVS): triad of postcricoid dysphagia, upper esophageal webs, and iron deficiency anemia
- ♂: < 14 g/dL
- ♀: < 12 g/dL
- Hematocrit: ↓ ; normal range in ♂: 42–50%; in ♀: 36–44%;
Complete blood count: typically microcytic, hypochromic anemia
- Red blood cell count (RBC): Initially normal; decreased (with prolonged deficiency)
- Mean corpuscular volume (MCV): ↓ (microcytic); Normal range: 70–100 fl
- Mean corpuscular hemoglobin: ↓ (hypochromic); Normal range: 25–35 pg
- WBC count and platelets: normal
- Reticulocyte count: ↓ or normal
- Red cell distribution width (RDW): ↑
- Peripheral blood smear: anisocytosis and increased zone of central pallor
- Iron studies
- Bone marrow biopsy: (rarely indicated): Indicated in patients with suspected IDA anemia and nondiagnostic iron studies ; low bone marrow iron is diagnostic of IDA
- Stool tests: Indicated in all patients with IDA
- Colonoscopy and upper GI endoscopy: can detect underlying GI malignancy, ulcerative/inflammatory causes of GI blood loss, Celiac disease
- Evaluation for , , , etc., depends on the patient's symptoms and physical findings
- Dietary modifications
Oral iron therapy: indicated in all patients with IDA (who can tolerate it)
- Available forms (ferrous preparations): ferrous sulfate, ferrous fumarate, and ferrous gluconate
- Adverse effects: gastrointestinal discomfort, black discoloration of stool
Parenteral iron therapy
- Indicated in
- Available forms (ferric preparations): iron dextran, sodium ferric gluconate, and iron sucrose
- Adverse effects: Thrombophlebitis; iron dextran can cause myalgia, arthralgia, headaches, and rarely, anaphylactic shock within 1–2 days of infusion.
- Blood transfusion
- Treat the underlying disease (e.g., antihelminthics for hookworm, NSAIDs and/or OCPs for menorrhagia)
- Response to treatment: Clinical symptoms rapidly improve; Hb should rise by 1 g/dL every 2–3 weeks.
- Monitoring: Check Hb and reticulocyte level 2 weeks after oral therapy or 4 weeks after parenteral therapy.
- IDA should be differentiated from other causes of microcytic anemia.
- (esp. in children)
- co-exist with IDA) (may
|Iron deficiency anemia||Anemia of chronic disease|
|Ferritin||↓||= to ↑|
|Iron||↓||= to ↓|
|Transferrin saturation||↓||= to slightly ↓|
See "Diagnostics" in learning card on microcytic anemia.for a table on differentiating features of types of
The differential diagnoses listed here are not exhaustive.