From the Guidelines
Low ferritin levels with normal iron levels indicate iron depletion, and supplementation is necessary to prevent progression to iron deficiency anemia, as evidenced by the most recent guidelines 1. When evaluating a patient with low ferritin but normal iron levels, it is essential to consider the underlying causes of iron depletion, such as blood loss, dietary insufficiency, or malabsorption conditions.
- Key laboratory tests to confirm iron depletion include serum ferritin, transferrin saturation, and mean cell hemoglobin (MCH) 1.
- A serum ferritin level of <15 μg/L is highly specific for iron deficiency, while a level of <30 μg/L indicates low body iron stores 1.
- In the presence of inflammation, a serum ferritin cut-off of 45 μg/L provides a respectable specificity for iron deficiency 1. The recommended treatment for iron depletion is oral iron supplementation, such as ferrous sulfate (325 mg) once or twice daily, taken between meals with vitamin C to enhance absorption 1. Additional considerations include:
- Consuming iron-rich foods like lean red meat, beans, spinach, and fortified cereals to support iron replenishment.
- Avoiding taking iron with calcium, dairy, coffee, tea, or antacids, which can reduce absorption.
- Monitoring for side effects like constipation, nausea, and black stools, and consulting a healthcare provider if symptoms like extreme fatigue, shortness of breath, or dizziness develop 1.
From the Research
Low Ferritin but Normal Iron
- Low ferritin levels can indicate iron deficiency, even if iron levels are normal 2
- Iron deficiency can be caused by various factors, including bleeding, impaired iron absorption, inadequate dietary iron intake, and pregnancy 2
- Serum ferritin is a key marker for diagnosing iron deficiency, and a level of <30 ng/mL is typically considered indicative of iron deficiency 2
- However, in the presence of systemic inflammation, serum ferritin levels may be elevated, making it challenging to diagnose iron deficiency 3
- The serum ferritin/C-reactive protein ratio has been proposed as a simple and effective biomarker for diagnosing iron deficiency in the context of systemic inflammation, with a threshold of ≤6 demonstrating high predictive power 3
- Intravenous iron supplementation therapy may be necessary for patients with iron deficiency anemia who are intolerant or unresponsive to oral iron, or who require rapid correction of their iron deficit 4
- Optimal serum ferritin level ranges are still being researched, but it is suggested that levels between 20-100 ng/mL may be associated with reduced cardiovascular mortality 5
- It is essential to consider the clinical context and other laboratory results when interpreting serum ferritin levels, as they can be influenced by various factors, including inflammation and iron status 2, 6, 3, 4, 5