How do we treat low ferritin levels?

Treatment of Low Ferritin vs. Low Iron

We treat low ferritin levels, not just low iron, because ferritin is the most specific indicator of depleted iron stores and guides the need for iron supplementation, even in the absence of anemia. 1, 2

Why Ferritin Matters More Than Serum Iron

• Serum ferritin is the earliest and most specific indicator of iron deficiency, reflecting total body iron stores where 1 μg/L of serum ferritin equals approximately 10 mg of stored iron 1
• Serum iron and transferrin saturation have high day-to-day variation and are less reliable for assessing iron stores 1
• Low ferritin (<30 μg/L in adults, <15 μg/L in children 6-12 years) indicates depleted iron stores requiring treatment, even when hemoglobin is normal 2, 3
• In inflammatory conditions or cancer, ferritin cutoffs should be raised to <100 ng/mL since inflammation falsely elevates ferritin levels 1

Diagnostic Thresholds for Treatment

Non-Anemic Iron Deficiency

• Treat when serum ferritin is <30 μg/L in healthy adults >15 years 2, 3
• For children 6-12 years: treat at ferritin <15 μg/L 3
• For adolescents 12-15 years: treat at ferritin <20 μg/L 3
• Confirm with transferrin saturation <20% when ferritin results are ambiguous 1, 2

Iron Deficiency Anemia

• Ferritin ≤15 μg/L with low hemoglobin confirms iron deficiency anemia 1, 2
• Among women with anemia, ferritin >15 μg/L suggests iron deficiency is NOT the cause (98% specificity) 1

Treatment Algorithm

First-Line: Oral Iron Supplementation

Dosing Strategy:

• Use preparations containing 28-50 mg elemental iron to minimize gastrointestinal side effects while maintaining efficacy 3
• Consider alternate-day dosing to improve absorption and reduce side effects 2
• A 27 mg daily dose corrects both mild anemia and storage iron depletion within 1 month, while 9 mg doses are insufficient for replenishing stores 4

Absorption Enhancement:

• Take iron with vitamin C to enhance non-heme iron absorption 2
• Avoid tea, coffee, or calcium-containing foods within 2 hours of iron supplementation 2
• Emphasize dietary heme iron sources (meat, seafood) which have higher bioavailability 2

Monitoring:

• Repeat serum ferritin and hemoglobin after 8-10 weeks of treatment 2, 3
• Target ferritin level of 50-100 μg/L for adequate iron stores 2
• For patients with recurrent low ferritin, monitor every 6 months during maintenance therapy 2, 3

Second-Line: Intravenous Iron

Indications for IV Iron:

• Failure of oral therapy despite adequate compliance 2
• Malabsorption disorders 2
• Need for rapid iron repletion 2
• In patients with ferritin ≤15 ng/mL and significant fatigue, IV iron (800 mg iron-hydroxide sucrose) reduces fatigue more effectively than oral iron 5

IV Iron Formulations and Dosing:

• Ferric carboxymaltose: maximum 1000 mg per week, minimum infusion time 15 minutes 1
• Iron isomaltoside: maximum 20 mg/kg (up to 1000 mg), minimum infusion time 15 minutes 1
• Iron sucrose: maximum 200-500 mg per dose, minimum infusion time 30-210 minutes 1
• Monitor serum ferritin and preferably keep below 500 mg/L to avoid iron overload toxicity, especially in children and adolescents 1

Critical Pitfalls to Avoid

• Do not treat with iron when ferritin is normal or elevated—this causes iron overload and is potentially harmful 3, 6
• Always exclude inflammation (check C-reactive protein) before interpreting ferritin, as acute phase reactions cause falsely elevated ferritin despite true iron deficiency 1, 3
• Do not discontinue treatment once symptoms improve—continue until iron stores are adequately replenished (ferritin 50-100 μg/L) 2
• Serum iron determinations may not be meaningful for 3 weeks following iron dextran administration 6
• Overtreatment with long-term daily oral or IV iron in the presence of normal ferritin is not recommended and potentially harmful 3

Special Populations

High-Risk Groups Requiring Screening:

• Adolescents, women with heavy menstrual bleeding, high-performance athletes, vegetarians/vegans, patients with eating disorders 3
• Screen male athletes once yearly and female athletes twice yearly 2
• Address underlying gynecological issues contributing to iron loss in women with heavy menstrual bleeding 2

Cancer Patients:

• Use higher ferritin cutoff (<100 ng/mL) due to inflammatory state 1
• IV iron supplementation (total doses ~1000 mg) significantly improves response to erythropoiesis-stimulating agents 1
• Oral iron does not result in better outcomes compared to no iron in cancer patients 1