Diagnosis: Microcytic Hypochromic Iron Deficiency Anemia
This patient has microcytic hypochromic anemia with laboratory values strongly suggesting iron deficiency anemia (IDA), and the first-line treatment is oral ferrous sulfate 324 mg (65 mg elemental iron) one to three times daily for at least three months after hemoglobin normalizes to replenish iron stores. 1, 2
Diagnostic Interpretation
The laboratory values confirm microcytic hypochromic anemia:
- Hemoglobin 10.2 g/dL indicates moderate anemia (defined as Hb ≤9.9 and ≥8.0 g/dL by some criteria, though this is borderline mild-moderate) 3
- MCH 23.9 pg (low, normal ~27-31 pg) indicates hypochromia and is more reliable than MCV as a marker of iron deficiency 1
- MCHC 30.1 g/dL (low, normal ~32-36 g/dL) confirms hypochromia 1
- RDW 18.1% (elevated, >14.0%) combined with low MCV strongly suggests iron deficiency anemia rather than thalassemia minor 1, 2
Essential Diagnostic Workup Before Treatment
Measure serum ferritin immediately - this is the single most useful marker for iron deficiency anemia, 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 in practice 1, 2.
Check transferrin saturation (TSAT) - this is more sensitive than hemoglobin alone for detecting iron deficiency and should be added if ferritin is falsely elevated due to inflammation 1, 2. Low TSAT with low ferritin confirms iron deficiency 2.
Investigate the source of iron loss - in adults with confirmed iron deficiency, 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. Consider fecal occult blood testing and potentially endoscopy 4.
Screen for celiac disease if malabsorption is suspected, as this is a common cause of refractory iron deficiency 1.
Treatment Algorithm
First-Line: Oral Iron Supplementation
Initiate oral ferrous sulfate 324 mg (65 mg elemental iron) one to three times daily for at least three months after hemoglobin normalizes to replenish iron stores 1, 2. This is the first-line treatment recommended by the American Gastroenterological Association 1.
Alternative oral formulations include ferrous gluconate or ferrous fumarate if ferrous sulfate causes intolerable gastrointestinal side effects (nausea, flatulence, diarrhea) 3, 1, 2.
Add ascorbic acid (vitamin C) to enhance iron absorption 1, 2.
Expected Response and Monitoring
Monitor hemoglobin weekly initially - a good response is defined as hemoglobin rise ≥10 g/L (≥1 g/dL) within 2 weeks, which confirms iron deficiency 1, 2.
Expected hemoglobin increase should be at least 2 g/dL within 4 weeks of starting treatment 1, 2.
Check hemoglobin, MCV, and iron studies at 2 weeks, 4 weeks, 3 months, and every 3 months for the first year, then annually thereafter 1, 2.
Second-Line: Intravenous Iron
Consider intravenous iron if the patient fails to respond to oral iron therapy, has malabsorption, or cannot tolerate oral iron 1, 2. Options include iron sucrose or iron gluconate 2.
For patients with mild anemia (Hb >10 g/dL), 100 mg/day oral iron sulfate can be adequate 3.
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. If the patient has normal iron studies with microcytosis, order hemoglobin electrophoresis to rule out thalassemia, especially with appropriate ethnic background or MCV disproportionately low relative to degree of anemia 1.
Do not overlook combined deficiencies - iron deficiency can coexist with B12 or folate deficiency 1. Check vitamin B12 and folate levels at least annually or if macrocytosis is present 3.
Evaluate inflammatory status - ferritin is an acute-phase reactant and can be falsely elevated in inflammation 3. In the presence of biochemical inflammation (elevated CRP), the lower limit of ferritin consistent with normal iron stores should be increased to 100 μg/L 3.
Provide additional oral iron if hemoglobin or MCV falls below normal during follow-up, as recurrence of anemia is common (>50% after 1 year) 3, 2.
Special Considerations for Refractory Cases
If the patient fails to respond to oral iron, evaluate for:
- Genetic disorders of iron metabolism (IRIDA/TMPRSS6 mutations) - characterized by very low TSAT, low-to-normal ferritin, and resistance to oral iron, requiring intravenous iron 1, 2
- Sideroblastic anemia (ALAS2 defects) - may respond to pyridoxine (vitamin B6) 50-200 mg daily initially, with lifelong supplementation at 10-100 mg daily 1, 2
- Ongoing blood loss or malabsorption disorders 1
Monitor for iron overload in patients receiving multiple transfusions or long-term iron therapy, and consider MRI of the liver in specific cases to detect toxic iron loading early 1, 2.