Microcytic Hypochromic Anemia: Diagnostic and Treatment Approach
Your lab values (MCV 77.7, MCH 23.6, MCHC 30.4) indicate microcytic hypochromic anemia, most likely iron deficiency anemia, and you should start oral ferrous sulfate 200 mg three times daily while simultaneously investigating the underlying cause of iron loss. 1
Immediate Diagnostic Workup
The combination of low MCV, low MCH, and low MCHC strongly suggests iron deficiency as the most likely diagnosis. 2 However, confirmation requires:
- Serum ferritin is the single most useful test, with levels <15 μg/L indicating absent iron stores and <30 μg/L indicating low body iron stores 1, 2
- A cut-off of 45 μg/L provides optimal sensitivity and specificity for iron deficiency in clinical practice 1, 2
- Transferrin saturation <16% confirms iron deficiency, particularly if ferritin is borderline or inflammation is present 2
- Check RDW (red cell distribution width): A low MCV with RDW >14.0% suggests iron deficiency, while RDW ≤14.0% suggests thalassemia minor 1
Critical Pitfall to Avoid
Do not assume all microcytic anemia is iron deficiency—you must differentiate from anemia of chronic disease, thalassemia, and sideroblastic anemia to avoid unnecessary or potentially harmful iron therapy. 1 In the presence of inflammation, ferritin up to 100 μg/L may still be consistent with iron deficiency. 2
First-Line Treatment
Start oral ferrous sulfate 200 mg three times daily for at least three months after correction of anemia to replenish iron stores. 1 Each 324 mg tablet of ferrous sulfate contains 65 mg of elemental iron. 3
- Alternative formulations include ferrous gluconate or ferrous fumarate if ferrous sulfate is not tolerated 1
- Adding ascorbic acid (vitamin C) enhances iron absorption 1, 2
- Do not crush or chew tablets 3
Expected Response
- Hemoglobin should rise ≥10 g/L (≥1 g/dL) within 2 weeks, confirming iron deficiency 1, 2
- Expect hemoglobin increase of at least 2 g/dL within 4 weeks of starting treatment 1
Mandatory Investigation of Underlying Cause
You must investigate the source of iron loss in adults with confirmed iron deficiency. 1 This is not optional—iron deficiency in adults requires explanation:
- Men with Hb <110 g/L or non-menstruating women with Hb <100 g/L warrant fast-track gastrointestinal referral 1
- Evaluate for gastrointestinal blood loss through history of melena, hematochezia, or occult bleeding 1
- Screen for celiac disease if malabsorption is suspected 1
- Consider menstrual losses, pregnancy, or dietary insufficiency in appropriate populations 4
Monitoring Protocol
- Monitor hemoglobin and red cell indices at three-monthly intervals for one year, then after a further year 1
- Provide additional oral iron if hemoglobin or MCV falls below normal 1
- Check serum ferritin and transferrin saturation to assess iron store repletion 1
Management of Treatment Failure
If no response within 2-4 weeks, consider:
- Intravenous iron if malabsorption is present, with expected hemoglobin increase of at least 2 g/dL within 4 weeks 1
- Hemoglobin electrophoresis if microcytosis persists with normal iron studies, appropriate ethnic background, or MCV disproportionately low relative to degree of anemia 1
- Genetic disorders of iron metabolism (TMPRSS6/IRIDA, SLC11A2 defects) if ferritin is low-normal with low transferrin saturation or family history of refractory anemia 1
- Pyridoxine (vitamin B6) 50-200 mg daily for X-linked sideroblastic anemia (ALAS2 defects), with lifelong maintenance at 10-100 mg daily 1
Special Consideration for Inflammation
In inflammatory bowel disease or chronic inflammatory conditions, serum ferritin <30 μg/L indicates iron deficiency in the absence of inflammation, but up to 100 μg/L may still be consistent with iron deficiency when inflammation is present. 5, 2 In these cases, MCH is more reliable than MCV because it's less dependent on storage conditions and is reduced in both absolute and functional iron deficiency. 1