What is the treatment for low ferritin (iron deficiency)?

Treatment of Low Ferritin (Iron Deficiency)

Start with oral iron supplementation at 100-200 mg of elemental iron daily for most patients with low ferritin, reserving intravenous iron for those with malabsorption, oral intolerance, severe deficiency requiring rapid repletion, or inflammatory conditions. 1, 2, 3

Diagnostic Thresholds

• Ferritin <30 ng/mL indicates absolute iron deficiency in patients without inflammatory conditions 1, 3
• The American Gastroenterological Association recommends a ferritin cutoff of 45 ng/mL in individuals with anemia for optimal sensitivity and specificity 1
• In inflammatory conditions (IBD, cancer, chronic kidney disease, heart failure), ferritin may be falsely elevated; iron deficiency can exist with ferritin <100 ng/mL 1
• Confirm iron deficiency in inflammatory states using transferrin saturation <20% or soluble transferrin receptor 1

First-Line: Oral Iron Therapy

Ferrous sulfate 325 mg daily (containing 65 mg elemental iron) is the standard first-line treatment due to low cost and proven efficacy 4, 3

Dosing Strategy

• 100-200 mg elemental iron daily in divided doses is the typical therapeutic range 2, 5, 3
• Alternate-day dosing may improve absorption and reduce gastrointestinal side effects compared to daily dosing 2, 6
• Take on an empty stomach for optimal absorption, though taking with food is acceptable if better tolerated 1

Enhancing Absorption

• Co-administer with 500 mg vitamin C to enhance non-heme iron absorption 1, 2
• Take with meat protein when feasible to improve absorption 1
• Avoid tea and coffee around dosing times as they contain polyphenols that inhibit iron absorption 2, 5

Expected Side Effects

• Gastrointestinal symptoms (constipation, diarrhea, nausea) are common and the primary cause of non-compliance 1, 2
• Using preparations with 28-50 mg elemental iron may reduce side effects while maintaining efficacy 5

Monitoring Response

• Recheck hemoglobin and ferritin after 8-10 weeks of oral therapy 5
• If hemoglobin increases after 4 weeks, continue therapy and monitor periodically 1
• If no response after 4 weeks, consider functional iron deficiency or switch to intravenous iron 1

Intravenous Iron Therapy

IV iron is indicated when oral iron fails, is not tolerated, or in specific clinical scenarios requiring rapid repletion. 1, 2, 3

Clear Indications for IV Iron

• Inflammatory bowel disease with active inflammation and compromised absorption 1, 5
• Chronic kidney disease, heart failure, or cancer with functional iron deficiency 1, 3
• Second and third trimesters of pregnancy 3
• Malabsorption conditions (celiac disease, post-bariatric surgery, atrophic gastritis) 1, 3
• Repeated failure of oral therapy or intolerance 2, 5
• Ongoing blood loss requiring rapid repletion 3
• Hemoglobin <100 g/L in IBD patients 2

IV Iron Administration

• Single dose of 1 gram IV iron over 15 minutes using modern carbohydrate-based formulations for significant deficiency 2
• IV iron has superior efficacy to oral iron in cancer patients receiving erythropoiesis-stimulating agents 1
• Iron sucrose, ferric gluconate, and low-molecular-weight iron dextran are available options 1

Safety Considerations

• Risk minimization is essential as infusion reactions can be life-threatening 2
• Monitor for allergic reactions, hypophosphatemia/osteomalacia, iron overload, and vascular leakage 7

Special Clinical Scenarios

Functional Iron Deficiency

• Defined as ferritin <800 ng/mL and transferrin saturation <20% 1
• Common in patients receiving erythropoiesis-stimulating agents for cancer-related anemia 1
• IV iron supplementation is superior to oral in this setting 1

Inflammatory Conditions

• Inflammation upregulates hepcidin, blocking iron release from macrophages and blunting response to oral iron 1
• Consider IV iron as first-line in active IBD, chronic kidney disease, or heart failure 1, 2

Celiac Disease

• Ensure adherence to gluten-free diet to improve iron absorption 1
• Start with oral iron based on severity and tolerance, then switch to IV if stores don't improve 1

Critical Pitfalls to Avoid

• Do not supplement iron when ferritin is normal or elevated (>100 ng/mL without inflammation) as this is potentially harmful 2, 5
• Do not miss iron deficiency in inflammatory states by relying solely on ferritin; use transferrin saturation 1
• Do not ignore dietary factors: counsel on vitamin C enhancement and tea/coffee inhibition 1, 2
• Do not continue oral iron indefinitely without monitoring; recheck labs at 8-10 weeks 5
• Do not use daily high-dose oral iron when alternate-day dosing may be better tolerated and absorbed 2, 6