In a 17‑year‑old female with mild anemia (hemoglobin 11.8 g/dL, hematocrit 35.2 %) and otherwise normal thyroid studies, MCH, MCHC, and AST, which laboratory tests should be ordered and what medication should be started?

Laboratory Evaluation and Treatment for Mild Microcytic Anemia in an Adolescent Female

Order a complete iron panel (serum ferritin, transferrin saturation, serum iron, and TIBC) along with C-reactive protein, and immediately start oral ferrous sulfate 60 mg daily while awaiting results. 1, 2, 3

Diagnostic Rationale

Your patient has mild microcytic hypochromic anemia based on:

• Hemoglobin 11.8 g/dL (WHO threshold for anemia in females is <12 g/dL) 3, 4
• Low MCH 26.9 pg (most sensitive early marker of iron deficiency, normal >27 pg) 2, 3
• Low MCHC 33.5 g/dL (confirms hypochromia, normal >34 g/dL) 2, 3
• Hematocrit 35.2% (below normal 36–46%) 3

Iron deficiency is the most common cause of microcytic anemia in adolescent females, affecting 15–50% of this population due to menstrual blood loss, rapid growth, and inadequate dietary iron intake. 3

Required Laboratory Tests

First-Line Iron Studies (Order All Together)

• Serum ferritin – the single most powerful test for iron deficiency; <30 μg/L confirms depleted iron stores when inflammation is absent 1, 2, 3, 5
• Transferrin saturation (TSAT) – <15–16% supports iron deficiency and is less affected by inflammation than ferritin 1, 2, 3, 5
• Serum iron and TIBC – elevated TIBC reflects the body's compensatory attempt to capture more circulating iron 3, 5
• C-reactive protein (CRP) – essential because ferritin rises as an acute-phase reactant; inflammation can falsely elevate ferritin and mask true iron deficiency 2, 3, 5

Why These Tests Matter

Do not rely on hemoglobin and hematocrit alone—normal ranges do not exclude iron deficiency because they decrease only when severe depletion is present. 6 Many iron-depleted individuals show normal CBC parameters but have reduced serum iron and ferritin, and ordering CBC alone without iron studies leads to missed diagnoses. 6

MCH falls before MCV in early iron deficiency, making it a more sensitive marker than mean corpuscular volume. 2, 3 Your patient's MCH of 26.9 pg indicates iron-restricted erythropoiesis even though severe microcytosis may not yet be present. 2

Medication: Empiric Iron Therapy

Start Immediately (Do Not Wait for Lab Results)

Prescribe oral ferrous sulfate 60 mg elemental iron once daily, taken between meals on an empty stomach to maximize absorption. 1, 3 Adolescent females with mild anemia require one 60-mg tablet daily according to CDC guidelines. 1

Dietary Counseling

• Advise consumption of iron-rich foods: red meat, poultry, fish, fortified cereals, beans, lentils 1, 3
• Recommend vitamin C–rich foods (citrus, tomatoes) with iron supplements to enhance absorption 2, 3
• Screen for vegetarian or vegan diet, which increases iron deficiency risk in adolescents 2

Response Assessment and Follow-Up

4-Week Recheck

Re-measure hemoglobin and hematocrit at 4 weeks; an increase of ≥1 g/dL (or hematocrit ≥3%) confirms iron-deficiency anemia even if baseline iron studies were equivocal. 1, 2, 3 This therapeutic response validates the diagnosis and warrants continuation of therapy for an additional 3 months (total 4 months) to replenish iron stores. 1, 3

If No Response After 4 Weeks

Order hemoglobin electrophoresis to exclude thalassemia trait, particularly in patients of African, Mediterranean, or Southeast Asian ancestry. 1, 2 Thalassemia minor typically shows:

• RDW ≤14% (versus >14% in iron deficiency) 1, 2
• Normal or borderline iron studies 2
• MCV disproportionately low relative to degree of anemia 1, 2

Screen for celiac disease with tissue transglutaminase (tTG) antibodies if malabsorption is suspected, as celiac disease is present in 2–5% of iron-deficiency anemia cases. 2, 3

Investigation of Underlying Cause

Menstrual History

In premenopausal women, menstrual blood loss is the most common cause of iron deficiency, but gastrointestinal sources must be considered if menstrual losses seem inadequate to explain the deficiency. 3 Assess for heavy menstrual bleeding (>80 mL per cycle or >7 days duration), which may necessitate gynecologic referral. 3

Gastrointestinal Evaluation

Take a careful history of NSAID use, gastrointestinal symptoms (melena, hematochezia, abdominal pain), and dietary factors. 3 Although gastrointestinal investigation is mandatory in postmenopausal women and adult males with iron deficiency, it is not first-line in adolescent females unless menstrual losses are insufficient to explain the anemia or GI symptoms are present. 3, 5

Critical Pitfalls to Avoid

• Do not rely on ferritin alone without CRP—inflammation falsely elevates ferritin and masks true iron deficiency 2, 3, 5
• Do not assume normal MCV excludes iron deficiency—MCH falls first in early deficiency 2, 3
• Do not limit evaluation to CBC alone—iron studies are required for proper diagnosis 3, 6
• Do not order hemoglobin electrophoresis as a first-line test—it is costly and unnecessary when iron studies are abnormal 2
• Do not discontinue iron therapy once hemoglobin normalizes—continue for 3–6 months to replenish iron stores 3

Treatment Duration and Monitoring

Continue oral iron for 3 months after hemoglobin normalizes to replenish body iron stores, then recheck ferritin to confirm adequacy (target >30 ng/mL). 3, 5 Anemia recurs in >50% of patients within one year, often indicating ongoing blood loss or inadequate iron stores, so long-term monitoring is essential. 3