Iron Deficiency with Depleted Iron Stores
This 19-year-old female has iron deficiency with depleted iron stores, confirmed by low ferritin (12 µg/L) and low transferrin saturation (13%), requiring immediate investigation of the underlying cause and initiation of iron replacement therapy. 1, 2
Diagnosis Interpretation
The laboratory pattern is diagnostic for iron deficiency:
- Ferritin 12 µg/L is below the 15 µg/L threshold, which has 100% specificity for depleted iron stores in women of childbearing age 1
- Transferrin saturation 13% is well below the 16% diagnostic threshold for iron deficiency in adults 1, 2, 3
- The combination of low ferritin (<15 µg/L) and low TSAT (<16%) confirms absolute iron deficiency with empty iron stores 1, 2
Critical point: Normal serum iron (55) and normal TIBC (424) do not exclude iron deficiency—these parameters have high day-to-day variability and are affected by recent meals, diurnal variation, and inflammation 1. Ferritin and transferrin saturation are far more reliable diagnostic markers 1, 2.
Mandatory Evaluation for Underlying Cause
Iron deficiency in a 19-year-old female rarely occurs without an identifiable source. You must investigate:
Primary Considerations:
- Menstrual blood loss: Assess menstrual history for heavy or prolonged periods (menorrhagia), which is the most common cause in premenopausal women 3, 4
- Dietary insufficiency: Evaluate for restrictive diets, vegetarian/vegan diet without supplementation, or eating disorders 3
- Gastrointestinal blood loss: Obtain stool guaiac testing to screen for occult GI bleeding 3
Additional Workup:
- Complete blood count (CBC) with hemoglobin, hematocrit, MCV, and reticulocyte count to assess severity of anemia and bone marrow response 3
- C-reactive protein (CRP) to exclude inflammation that could mask iron deficiency 3
- Malabsorption screening: Consider celiac disease serology (tissue transglutaminase antibody) if dietary intake appears adequate 3
- NSAID use history: Chronic NSAID use can cause occult GI bleeding 3
Treatment Algorithm
First-Line: Oral Iron Supplementation
Initiate oral ferrous sulfate 325 mg (65 mg elemental iron) once or twice daily 4
- Oral iron is preferred in young, otherwise healthy women without chronic inflammatory conditions 4
- Take on an empty stomach to maximize absorption, or with food if gastrointestinal side effects occur 4
- Avoid taking with calcium, antacids, or proton pump inhibitors which impair absorption 3
Treatment Targets:
- Ferritin ≥30–45 ng/mL in patients without chronic inflammation 2, 3
- Transferrin saturation ≥20% to ensure adequate iron availability for erythropoiesis 2, 4
- Hemoglobin increase of 1–2 g/dL within 4–8 weeks indicates adequate response 2
When to Consider Intravenous Iron:
- Intolerance to oral iron due to gastrointestinal side effects
- No hematologic response after 4–8 weeks of adequate oral therapy
- Ongoing blood loss exceeds replacement capacity
- Malabsorption disorder is identified
Monitoring and Follow-Up
- Recheck iron parameters (ferritin, TSAT, CBC) at 4–8 weeks after initiating therapy 2, 3
- Continue iron supplementation for 3–6 months after correction to replenish iron stores 3
- If menorrhagia is identified, coordinate with gynecology for management (hormonal contraception, tranexamic acid, or other interventions) 3
Common Pitfalls to Avoid
- Do not dismiss iron deficiency because serum iron is "normal"—serum iron has poor diagnostic accuracy and high variability 1, 5
- Do not assume dietary insufficiency is the only cause—always screen for GI blood loss, even in young women 3
- Do not stop iron therapy when hemoglobin normalizes—continue for 3–6 months to replenish stores 3
- Do not measure iron parameters within 4 weeks of starting oral iron—wait 4–8 weeks to assess true response 2