Anemia: Iron Deficiency vs. Anemia of Chronic Disease

Anemia is one of the most commonly tested topics in nursing because it touches on labs, medications, nutrition, and chronic disease management. This guide focuses on the two anemias you must be able to distinguish on exams: iron deficiency anemia (IDA) and anemia of chronic disease (ACD).

What Is Anemia?

• Anemia is a reduction in oxygen-carrying capacity caused by decreased red blood cells, hemoglobin, or hematocrit.
• Symptoms result from tissue hypoxia and include fatigue, pallor, weakness, and shortness of breath.

Classification of Anemia by MCV

• Microcytic (MCV < 80 fL): iron deficiency anemia, anemia of chronic disease, thalassemia
• Normocytic (MCV 80–100 fL): anemia of chronic disease, acute blood loss, hemolytic anemia, CKD
• Macrocytic (MCV > 100 fL): vitamin B12 deficiency, folate deficiency, alcoholism, liver disease

IDA vs. ACD at a Glance

Exam trick: Ferritin is low in IDA and normal or high in ACD. TIBC is high in IDA and low or normal in ACD.

Iron Deficiency Anemia (IDA)

• Occurs when the body has insufficient iron stores to produce hemoglobin.
• Produces microcytic (small) and hypochromic (pale) red blood cells.
• Common causes: chronic blood loss (GI bleeding, menorrhagia), poor dietary intake, malabsorption (gastric bypass, celiac disease).

Classic Clinical Signs

• Koilonychia — spoon-shaped nails
• Pica — craving for ice, dirt, or starch
• Glossitis — tongue inflammation
• Angular cheilitis — cracks at the corners of the mouth

Diagnosis

• Low ferritin (< 30 ng/mL) is the most specific test.
• Other labs: low serum iron, high TIBC, low transferrin saturation, low MCV, high RDW.

Treatment

• First line: oral iron (ferrous sulfate) on an empty stomach with vitamin C.
• Avoid calcium, antacids, and tea within 2–4 hours of the dose (they decrease absorption).
• IV iron for malabsorption, intolerance to oral iron, or severe deficiency.
• Identify and treat the underlying cause of blood loss.

Anemia of Chronic Disease (ACD)

• Caused by chronic inflammation (infection, autoimmune disease, malignancy, CKD).
• Inflammatory cytokines (IL-6, TNF-α) raise hepcidin, which blocks iron absorption and traps iron in storage sites.
• Results in functional iron deficiency despite adequate total body iron stores.
• Symptoms often masked by the underlying disease, but fatigue, pallor, and reduced exercise tolerance occur.

Diagnosis

• Normocytic anemia with low serum iron, low TIBC, low transferrin saturation, and normal or high ferritin.
• Elevated inflammatory markers (CRP, ESR).
• Key differentiator from IDA: ferritin is normal or high, not low.

Treatment

• Manage the underlying cause of inflammation.
• Erythropoiesis-stimulating agents (ESAs) such as epoetin alfa for anemia of CKD or chemotherapy-induced anemia.
• Iron supplementation is not effective unless iron deficiency is also present.

Oral Iron Therapy for IDA

• Ferrous sulfate is the most common oral preparation.
• Take on an empty stomach (1 hour before or 2 hours after meals).
• Take with vitamin C (orange juice) to enhance absorption.
• Separate from calcium, antacids, and tea by 2–4 hours.
• Common side effects: nausea, constipation, and dark stools (normal).
• Liquid iron stains teeth — take through a straw.
• Hemoglobin typically normalizes in 4–6 weeks.
• Continue therapy for 3–6 months after hemoglobin normalizes to replenish stores.

IV Iron and Erythropoiesis-Stimulating Agents

IV Iron

• Indicated for malabsorption, intolerance to oral iron, or severe deficiency.
• Examples: iron sucrose, ferric carboxymaltose, iron dextran.
• Iron dextran carries the highest risk of anaphylaxis and requires a test dose.
• Extravasation causes permanent brown skin staining.

ESAs (epoetin alfa, darbepoetin alfa)

• Used for anemia of CKD and chemotherapy-induced anemia.
• Target hemoglobin 10–11 g/dL; higher levels increase cardiovascular risk.
• Monitor for hypertension and thrombosis.
• Iron supplementation often required for adequate response.

Nursing Assessment

• Assess for fatigue, pallor, and shortness of breath.
• In suspected IDA, assess for bleeding: melena, hematemesis, menorrhagia.
• Look for pica, koilonychia, glossitis, angular cheilitis in IDA.
• Assess for signs of underlying chronic disease in ACD.
• Review medications that may cause GI bleeding (NSAIDs, aspirin).

Nursing Interventions

• Administer oral iron on an empty stomach with vitamin C.
• Separate iron from calcium, antacids, and tea by 2–4 hours.
• Teach that dark stools are normal and not a sign of bleeding.
• For liquid iron, instruct the patient to use a straw to prevent tooth staining.
• For IV iron, monitor for anaphylaxis during the infusion.
• For ESA therapy, monitor blood pressure and hemoglobin levels.

Patient Teaching

• Take iron on an empty stomach with orange juice for better absorption.
• Do not take iron with calcium, antacids, or tea.
• Expect dark green or black stools — this is normal.
• Use a straw for liquid iron to prevent tooth staining.
• Increase dietary iron: red meat, spinach, and beans.
• Continue iron therapy for 3–6 months after hemoglobin normalizes.
• For ACD, focus on treating the underlying condition and report worsening fatigue or shortness of breath.

Common Exam Traps

• Ferritin: low in IDA, normal or high in ACD.
• TIBC: high in IDA, low or normal in ACD.
• MCV: low in IDA, normal in ACD.
• RDW: high in IDA, normal in ACD.
• Pica and koilonychia are classic signs of IDA.
• Iron absorption is enhanced by vitamin C, decreased by calcium, antacids, and tea.
• IV iron — especially iron dextran — carries a risk of anaphylaxis.
• Target hemoglobin on ESAs is 10–11 g/dL.
• Ferritin is an acute-phase reactant and may be falsely elevated in inflammation.

Key Takeaways

• IDA = microcytic anemia with low ferritin and high TIBC, caused by blood loss or poor intake.
• ACD = normocytic anemia with normal/high ferritin and low/normal TIBC, driven by chronic inflammation and hepcidin.
• Treat IDA with oral ferrous sulfate on an empty stomach with vitamin C; avoid calcium, antacids, and tea.
• Treat ACD by managing the underlying cause; use ESAs for CKD or chemotherapy-induced anemia, targeting Hgb 10–11 g/dL.
• The two highest-yield differentiators between IDA and ACD are ferritin and TIBC.
• Watch for anaphylaxis with IV iron (especially iron dextran) and hypertension/thrombosis with ESAs.