Iron Deficiency Anemia (IDA) - Absolute Iron Deficiency
These results demonstrate severe absolute iron deficiency anemia requiring immediate iron replacement therapy and investigation for underlying blood loss, particularly from the gastrointestinal tract.
Laboratory Interpretation
Your results show:
- Hemoglobin 107 g/L: Mild anemia (below normal range of ~120-160 g/L for women, ~130-170 g/L for men)
- MCV 81 fL: Low-normal to mildly microcytic (normal 80-100 fL)
- MCH 25 pg: Hypochromic (low, normal ~27-33 pg)
- Ferritin 7 µg/L: Severely depleted iron stores (normal >30 µg/L)
- Transferrin saturation 0.5%: Critically low (normal >20%)
This constellation is diagnostic of absolute iron deficiency anemia. The extremely low ferritin (<20 µg/L) and transferrin saturation (<20%) confirm depleted iron stores and inadequate iron availability for erythropoiesis 1.
Clinical Significance
The severity of iron depletion (ferritin 7 µg/L, TSAT 0.5%) indicates this is not simply dietary insufficiency but likely represents ongoing blood loss. The body has exhausted its iron reserves and cannot produce adequate hemoglobin, as evidenced by the low MCH.
Key Points:
- Ferritin <20 µg/L is specific for absolute iron deficiency in the absence of chronic kidney disease or heart failure 1
- TSAT <20% confirms inadequate iron delivery to developing red blood cells 1, 2
- The MCV is only mildly reduced because it takes time for microcytosis to develop; MCH drops earlier in iron deficiency 3
Required Actions
1. Investigate the Source of Iron Loss
Most adults with confirmed IDA require evaluation of both upper and lower gastrointestinal tract to exclude malignancy and other treatable causes 1. This is critical because:
- GI blood loss is the most common cause in adults
- Colon cancer and gastric pathology must be excluded
- Dual pathology is common
Common pitfall: Assuming dietary insufficiency alone in adults without investigating for occult bleeding, which can delay cancer diagnosis.
2. Initiate Iron Replacement
Oral iron remains first-line treatment (e.g., ferrous sulfate 200 mg 2-3 times daily) 1. However, consider intravenous iron if:
- Oral iron is not tolerated (common side effects: constipation, nausea)
- Malabsorption is suspected
- Rapid correction is needed
- Patient has inflammatory bowel disease
3. Monitor Response
- Recheck hemoglobin and ferritin in 4-8 weeks
- Hemoglobin should rise by ~1 g/dL per month with adequate iron replacement
- Continue iron supplementation until ferritin >30 µg/L and hemoglobin normalizes
- Target ferritin >30-50 µg/L to replenish stores 4, 5
Special Considerations
If the patient has:
- Chronic kidney disease (GFR <60): Different thresholds apply; absolute iron deficiency defined as TSAT ≤20% with ferritin ≤100 µg/L 1
- Heart failure: Iron deficiency defined as ferritin <100 µg/L and/or TSAT <20%; consider IV iron for prognostic benefit 1
- Inflammatory bowel disease: Ferritin up to 100 µg/L may still reflect iron deficiency due to inflammation 1
In your case, without these comorbidities, the diagnosis is straightforward absolute iron deficiency anemia requiring treatment and investigation.