Iron Therapy in Anemia Management

Introduction to Iron Deficiency

The decision to use IV iron must be guided by iron status tests together with hemoglobin levels, not hemoglobin alone, as recommended by the Kidney International Supplements guidelines 1
Iron supplementation works by correcting iron-restricted erythropoiesis—if iron stores are adequate, additional iron will not improve anemia and may cause harm, according to the Kidney International Supplements guidelines 1

Absolute iron deficiency is defined as ferritin <100 ng/mL or transferrin saturation <20% in most clinical contexts, as stated by the Kidney International Supplements guidelines 1, 2
Functional iron deficiency occurs in inflammatory states where ferritin may be elevated (500-1200 ng/mL) but transferrin saturation remains <25%, indicating inadequate iron availability for erythropoiesis despite seemingly adequate stores, according to the Kidney International Supplements guidelines 1, 3

The Kidney International Supplements guidelines recommend measuring both ferritin AND transferrin saturation to determine if iron deficiency exists 1, 2
If ferritin <100 ng/mL, absolute iron deficiency is present, as stated by the Kidney International Supplements guidelines 1, 2
If ferritin >500 ng/mL but transferrin saturation <20-25% in inflammatory conditions, functional iron deficiency may be present, according to the Kidney International Supplements guidelines 1, 3

IV iron is preferred over oral iron when hemoglobin <100 g/L (10 g/dL) with confirmed iron deficiency, as recommended by the Clinical Nutrition guidelines 4
IV iron may be used when active inflammatory disease is present, previous intolerance to oral iron, or patient requires ESAs, according to the Clinical Nutrition guidelines 4

Administering IV iron without iron deficiency carries risks without benefit, including infusion reactions, iron overload, and potential for infections and cardiovascular events, as stated by the Kidney International Supplements guidelines 3
Infusion reactions occur in 4.3% of patients receiving IV iron, according to the Kidney International Supplements guidelines 3

In chronic kidney disease patients on hemodialysis receiving ESAs, higher iron targets may be appropriate (ferritin >200 ng/mL, transferrin saturation >20%) to reduce ESA requirements, as recommended by the Kidney International Supplements guidelines 1, 2

The European Crohn's and Colitis Organisation recommends intravenous iron infusion when hemoglobin is below 10 g/dL in patients with iron deficiency anemia, particularly in those with active inflammatory conditions, intolerance to oral iron, or insufficient time before planned procedures 5, 6
IV iron is the preferred route when hemoglobin falls below 10 g/dL, as this represents severe anemia requiring rapid correction 5, 6, 7
This threshold applies across multiple clinical contexts including inflammatory bowel disease, chronic kidney disease, and cancer-related anemia 5, 8, 9

Active inflammatory disease warrants IV iron regardless of hemoglobin level due to functional iron deficiency and impaired oral absorption 5, 6
The American Gastroenterological Association suggests that oral iron can paradoxically worsen IBD through generation of reactive oxygen species 6, 7

The National Kidney Foundation recommends initiating IV iron when Hb <11 g/dL with ferritin <100 ng/mL or transferrin saturation <20% in chronic kidney disease patients 8, 9
The American Society of Clinical Oncology considers IV iron for cancer-related anemia with Hb <10 g/dL when transferrin saturation <20% 10

The European Crohn's and Colitis Organisation recommends proceeding directly to IV iron if Hb <10 g/dL 5, 6
The National Kidney Foundation suggests evaluating additional factors such as ferritin and transferrin saturation levels to confirm absolute iron deficiency requiring IV iron 8, 9

The European Renal Association advises against relying solely on ferritin levels in inflammatory states, as ferritin is an acute phase reactant and may be falsely elevated 8, 9
The American Gastroenterological Association recommends avoiding blood transfusion except for hemodynamic instability or severe symptomatic anemia, as effects are temporary and risks are significant 5, 7