Treatment for Low Ferritin Level of 3.7
Oral iron supplementation with ferrous sulfate 325 mg (65 mg elemental iron) daily is the recommended treatment for a severely depleted iron store with ferritin level of 3.7 μg/L. 1
Diagnosis and Significance
- A serum ferritin level of 3.7 μg/L indicates absolute iron deficiency, as it falls well below the diagnostic threshold of <15 μg/L that confirms depleted iron stores 2
- This extremely low ferritin level represents approximately 37 mg of stored iron in the body (1 μg/L of serum ferritin ≈ 10 mg of stored iron) 2
- Ferritin is the most specific indicator available for diagnosing depleted iron stores, with a specificity of 98% when levels are ≤15 μg/L 2
Treatment Approach
First-line Treatment:
- Oral iron supplementation with ferrous sulfate 325 mg (providing 65 mg of elemental iron) once daily 1
- Alternative: Ferrous fumarate 325 mg daily may be used if better tolerated 3
- Treatment should continue until ferritin levels normalize (>50 μg/L) and hemoglobin returns to normal range 2
Monitoring and Duration:
- Check hemoglobin and ferritin levels after 4-8 weeks of treatment 2
- Continue treatment for at least 3 months after normalization of hemoglobin to replenish iron stores 2
- Long-term monitoring is warranted to detect recurrence, with follow-up every 6-12 months depending on risk factors 2
Special Considerations:
- If oral iron is not tolerated or ineffective (no increase in hemoglobin after 4 weeks), consider intravenous iron therapy 2
- For patients with inflammatory conditions, oral iron may be less effective due to hepcidin-mediated iron sequestration 2
- Transferrin saturation should also be monitored alongside ferritin, with a target of >16% 2
Potential Pitfalls and Caveats
- Ferritin is an acute-phase reactant; concurrent inflammation can mask iron deficiency by falsely elevating ferritin levels 2
- Recent research suggests that ferritin levels up to 50 μg/L may still indicate iron deficiency, especially in women 4, 5, 6
- Gastrointestinal side effects (constipation, nausea, abdominal discomfort) are common with oral iron supplements and may affect adherence 2
- Taking iron supplements with vitamin C can enhance absorption, while calcium, tea, coffee, and antacids can reduce absorption 2
- Investigate the underlying cause of iron deficiency (blood loss, malabsorption, poor dietary intake) while treating the deficiency 2, 6
Evaluation of Underlying Causes
- Consider gastrointestinal evaluation for occult bleeding, especially in elderly patients, even with isolated low ferritin without anemia 6
- Assess dietary intake of iron-rich foods and potential malabsorption issues 2
- In women of reproductive age, evaluate for heavy menstrual bleeding 2
- Monitor for recurrence of iron deficiency, which may indicate persistent underlying pathology 2