How do you manage low ferritin levels versus iron deficiency?

Management of Low Ferritin versus Iron Deficiency

Treatment should be initiated for all patients with iron deficiency anemia, as well as those with low ferritin levels even without anemia, to correct deficiency and replenish iron stores. 1

Diagnostic Criteria

Iron Deficiency Diagnosis

• Non-inflammatory conditions:

  • Serum ferritin <30 μg/L indicates iron deficiency 2, 3
  • MCV <76 fl 1

• Inflammatory conditions:

  • Serum ferritin up to 100 μg/L may still represent iron deficiency 1, 2, 4
  • Transferrin saturation (TSAT) <20% 1, 2
  • CRP should be measured to assess inflammatory status 1, 2

• Additional markers:

  • Low mean corpuscular volume (MCV)
  • Raised red cell distribution width (RDW)
  • Reticulocyte hemoglobin content <30 pg 2

Treatment Algorithm

1. For Low Ferritin Without Anemia

• Oral iron supplementation:

  • Ferrous sulfate 200 mg three times daily (65 mg elemental iron per tablet) 1, 5
  • Alternative: ferrous gluconate or ferrous fumarate 1
  • Continue for 3 months after correction of deficiency to replenish stores 1
  • Consider alternate-day dosing for better absorption and fewer side effects 1

• Dietary recommendations:

  • Increase consumption of iron-rich foods
  • Include vitamin C with meals to enhance iron absorption 2
  • Avoid tea, coffee, calcium, or antacids with iron supplements 2

2. For Iron Deficiency Anemia

• First-line treatment:

  • Same oral iron regimen as above for mild anemia and clinically inactive disease 1
  • Continue for 3 months after normalization of hemoglobin 1

• Consider IV iron as first-line in:

  • Clinically active inflammatory disease 1
  • Previous intolerance to oral iron 1
  • Hemoglobin below 100 g/L 1
  • Patients needing erythropoiesis-stimulating agents 1
  • Malabsorption conditions 3

3. IV Iron Administration

• Options include:
  • Ferric carboxymaltose: up to 1000 mg iron over 15 minutes 1
  • Iron sucrose: 200-500 mg over 30-210 minutes 1
  • Iron isomaltoside: up to 20 mg/kg (maximum 1000 mg) over 15 minutes 1

Monitoring Response

• Repeat hemoglobin, MCV, and ferritin after 8-10 weeks of treatment 1, 3
• For IV iron, wait at least 8-10 weeks before measuring ferritin (falsely elevated immediately after infusion) 1
• Once normalized, monitor hemoglobin and red cell indices every three months for one year, then after another year 1
• Additional oral iron should be given if hemoglobin or MCV falls below normal 1

Special Considerations

Pre-menopausal Women

• Higher prevalence of iron deficiency (5-10%) 1
• Consider higher ferritin cutoffs (some evidence suggests 50 ng/mL as physiologic cutoff) 6
• Evaluate for menorrhagia using pictorial blood loss assessment charts 1

Inflammatory Conditions

• Higher ferritin cutoffs (up to 100 μg/L) should be used 1, 2, 4
• Consider both ferritin and transferrin saturation for diagnosis 4
• IV iron may be preferred over oral iron 1

Common Pitfalls

• Relying solely on ferritin in inflammatory conditions can miss iron deficiency 2, 4
• Stopping treatment too early before replenishing iron stores 1, 3
• Not considering IV iron when oral iron is ineffective or poorly tolerated 1, 3
• Continuing iron supplementation when ferritin is normal or high (potentially harmful) 1, 3
• Using outdated ferritin reference ranges that may underdiagnose iron deficiency in women 6

By following this structured approach to diagnosing and treating iron deficiency based on ferritin levels and inflammatory status, clinicians can effectively manage both low ferritin states and iron deficiency anemia to improve patient outcomes.