Should a patient with microcytic anemia, as indicated by a Mean Corpuscular Volume (MCV) of 71.4, Mean Corpuscular Hemoglobin (MCH) of 21.4, Mean Corpuscular Hemoglobin Concentration (MCHC) of 30.0, and Red Cell Distribution Width (RDW) of 15.7, be started on oral iron supplements?

Should This Patient Be Started on Oral Iron Supplementation?

Yes, this patient should be started on oral iron supplementation immediately, as the CBC findings strongly suggest iron deficiency anemia with an MCV of 71.4 (severely microcytic), elevated RDW of 15.7, and hypochromic indices. 1

Diagnostic Interpretation

The CBC pattern is highly characteristic of iron deficiency:

• MCV 71.4 with RDW 15.7 creates the classic diagnostic signature: a low MCV combined with elevated RDW (>14.0%) strongly indicates iron deficiency anemia rather than thalassemia minor, which typically presents with RDW ≤14.0% 1
• MCH 21.4 and MCHC 30.0 confirm hypochromic anemia, with MCH being particularly reliable as it's less dependent on storage conditions and is reduced in both absolute and functional iron deficiency 1
• This degree of microcytosis (MCV <75) with elevated RDW makes iron deficiency the most likely diagnosis 2, 3

Recommended Treatment Protocol

First-line therapy is oral iron supplementation with ferrous sulfate 200 mg three times daily for at least three months after correction of anemia to replenish iron stores. 1

Specific dosing considerations:

• Ferrous sulfate 200 mg three times daily provides 180-200 mg elemental iron daily 4
• Alternative formulations include ferrous gluconate or ferrous fumarate if ferrous sulfate is not tolerated 1
• Adding ascorbic acid can enhance iron absorption 1
• Take with meals to minimize gastrointestinal discomfort 5

Expected Response and Monitoring

A good response to iron therapy is defined as hemoglobin rise ≥10 g/L within a 2-week timeframe, which confirms iron deficiency. 1

• Monitor hemoglobin concentration and red cell indices at three-monthly intervals for one year, then after a further year 1
• If hemoglobin increases by at least 2 g/dL within 4 weeks, continue oral iron therapy 6
• Continue treatment for at least 3 months after anemia correction to replenish iron stores 1, 2

Critical Next Steps: Investigate the Underlying Cause

While starting iron supplementation, you must simultaneously investigate the source of iron loss, as iron deficiency in adults always requires explanation. 1

Essential workup includes:

• Serum ferritin level is the single most useful marker, with <15 μg/L indicating absent iron stores and <30 μg/L indicating low body iron stores 1
• A ferritin cut-off of 45 μg/L provides optimal sensitivity and specificity for iron deficiency 1
• Transferrin saturation (TSAT) should be measured, as TSAT <16-20% confirms iron deficiency 1
• Gastrointestinal evaluation is mandatory in men with Hb <110 g/L or non-menstruating women with Hb <100 g/L, warranting fast-track GI referral 1

Common sources to investigate:

• Gastrointestinal blood loss (ulcers, malignancy, inflammatory bowel disease) 6
• Menstrual blood loss in premenopausal women 6
• Malabsorption disorders (celiac disease, H. pylori infection, autoimmune atrophic gastritis) 1
• Dietary inadequacy (rare in developed countries) 2

When to Consider Alternative Diagnoses or Treatments

If the patient fails to respond to oral iron therapy within 2-4 weeks, consider:

• Non-compliance with medication 1
• Ongoing blood loss exceeding replacement capacity 2
• Malabsorption disorders requiring intravenous iron 1, 6
• True intolerance to oral preparations 6
• Rare genetic disorders such as IRIDA (iron-refractory iron deficiency anemia) if remarkably low TSAT with low-to-normal ferritin and failure to respond to oral iron 1

Switch to intravenous iron (iron sucrose or iron gluconate) if malabsorption is confirmed, with expected hemoglobin increase of at least 2 g/dL within 4 weeks. 1

Critical Pitfalls to Avoid

• Do not assume all microcytic anemia is iron deficiency: Anemia of chronic disease, thalassemia, and sideroblastic anemia must be differentiated to avoid unnecessary iron therapy 1
• Order hemoglobin electrophoresis if microcytosis persists with normal iron studies, appropriate ethnic background, or MCV disproportionately low relative to degree of anemia 1
• Consider genetic testing for disorders like SLC11A2, STEAP3, SLC25A38, ALAS2, or ABCB7 if extreme microcytosis (MCV <70) or family history present 1
• Monitor for iron overload if patient receives multiple transfusions or long-term iron therapy 1
• Avoid overlooking combined deficiencies, such as iron deficiency coexisting with B12 or folate deficiency 1

Special Warnings

• Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6 5
• Iron products should not be taken within two hours of tetracycline antibiotics due to absorption interference 5
• Occasional gastrointestinal discomfort, black stools, constipation, or diarrhea may occur 5