What are the next laboratory tests and appropriate iron therapy for a 17‑year‑old female with mild iron‑deficiency anemia (hemoglobin 11.8 g/dL, hematocrit 35.2%, MCH 26.9 pg, RDW 14.3)?

Next Steps for a 17-Year-Old Female with Mild Microcytic Anemia

Start empiric oral iron supplementation at 60–120 mg elemental iron daily taken between meals, recheck hemoglobin in 4 weeks, and order serum ferritin and red-cell distribution width (RDW) now to confirm iron deficiency. 1

Immediate Laboratory Work-Up

Your patient has mild microcytic anemia (hemoglobin 11.8 g/dL is below the 12.0 g/dL threshold for adolescent females, hematocrit 35.2% is below 36%, MCH 26.9 pg is low, and MCHC 33.5 g/dL is at the lower limit). 1 The most critical next laboratory tests are:

• Serum ferritin – A level < 15 µg/L confirms depleted iron stores and is the most specific marker for iron deficiency. 1, 2
• Red-cell distribution width (RDW) – An elevated RDW (> 14%) combined with low MCV strongly suggests iron-deficiency anemia, whereas a normal RDW (≤ 14%) with microcytosis points toward thalassemia trait. 1
• C-reactive protein (CRP) – Measure this to detect inflammation that can falsely elevate ferritin and mask iron deficiency; in the presence of elevated CRP, ferritin values up to 100 µg/L may still be compatible with iron deficiency. 1
• Transferrin saturation – A value < 20% indicates iron-restricted erythropoiesis. 1

Her RDW of 14.3% is borderline elevated, which favors iron deficiency over thalassemia trait. 1

Empiric Iron Therapy Protocol

Because she is an otherwise healthy adolescent girl who is not acutely ill, you may initiate a presumptive diagnosis of iron-deficiency anemia and start empiric iron therapy immediately while awaiting confirmatory ferritin results. 1 This approach is explicitly endorsed by the CDC. 3, 1

• Prescribe 60–120 mg elemental iron daily taken between meals to maximize absorption. 3, 1, 2
• Provide dietary counseling emphasizing iron-rich foods (especially heme sources such as meat, poultry, and fish, which have 15–35% bioavailability versus < 10% for plant-based non-heme iron) and concurrent vitamin C intake to enhance absorption. 1, 2
• Consider adding ascorbic acid (vitamin C) supplementation if dietary intake is inadequate. 2

Monitoring Response at 4 Weeks

• Recheck hemoglobin after 4 weeks of therapy. 3, 1, 2
• An increase of ≥ 1 g/dL hemoglobin (or ≥ 3% hematocrit) confirms iron-deficiency anemia and validates the empiric approach. 3, 1, 2
• If confirmed, continue iron supplementation for an additional 2–3 months (total of 3 months) to replenish iron stores. 3, 1, 2
• Reassess hemoglobin approximately 6 months after completing treatment. 1, 2

If No Response After 4 Weeks

If hemoglobin rises by < 1 g/dL despite documented adherence:

• Repeat MCV, RDW, and serum ferritin. 3, 1
• A ferritin ≥ 15 µg/L suggests an alternative etiology. 3, 1
• Consider hemoglobin electrophoresis to detect thalassemia trait or other hemoglobinopathies, especially if she is of African, Mediterranean, or Southeast Asian ancestry. 3, 1
• Obtain vitamin B12 and folate levels if macrocytosis or mixed indices are present. 1
• Seek hematology consultation if the etiology remains unclear. 1

Risk Factor Assessment

Adolescent girls with the following risk factors warrant annual screening and are appropriate candidates for empiric iron therapy: 1

• Heavy or prolonged menstrual bleeding (the leading risk factor for iron deficiency in this population) 1
• Low dietary iron intake or restrictive diets (vegetarian, vegan, low red-meat intake) 1
• Prior episode of iron-deficiency anemia 1
• Participation in high-impact or endurance sports 1

Assess her menstrual history and dietary intake carefully, as these are the most common underlying causes. 1, 2

Common Pitfalls to Avoid

• Do not skip the 4-week hemoglobin recheck – this step confirms the diagnosis and prevents inappropriate continuation or cessation of therapy. 1
• Do not discontinue iron as soon as hemoglobin normalizes – an additional 2–3 months of therapy is required to restore iron stores. 3, 1, 2
• Do not assume all microcytic anemia is due to iron deficiency – thalassemia trait typically presents with normal RDW and elevated red blood cell count despite microcytosis. 1
• Do not rely solely on ferritin in the presence of inflammation – concurrent CRP measurement is essential. 1
• Do not overlook the possibility of dual pathology – thalassemia trait carriers can still develop concurrent iron deficiency. 1