Iron Therapy Guidelines

Patient Selection

Patients with clinically active inflammatory bowel disease, previous intolerance to oral iron, hemoglobin below a certain threshold, or those who need erythropoiesis-stimulating agents may benefit from intravenous iron therapy, according to the Clinical Nutrition guideline 1
Patients with impaired iron absorption, such as those with post-bariatric surgery or celiac disease, may also require intravenous iron therapy 1
Patients with chronic kidney disease, inflammatory bowel disease, or other conditions that impair iron absorption may benefit from intravenous iron therapy, as recommended by the American Gastroenterological Association, with a strength of evidence rated as moderate 2

Ferritin levels <30 μg/L indicates iron deficiency in patients without inflammation, and <100 μg/L may indicate iron deficiency in the presence of inflammation 3

The following table summarizes the diagnostic parameters for iron deficiency:

Parameter	Iron Deficiency	Chronic Disease	Genetic Defects
Ferritin	Low (<30 μg/L)	Normal to high (>100 μg/L)	Variable (normal to high)
Serum Iron	Low	Low	Variable
Transferrin Saturation	Low (<20%)	Low (<20%)	Variable (low to high)
TIBC	Elevated	Normal to low	Low in hypotransferrinemia
MCV	Low (microcytic)	Usually normal	Low
RDW	Elevated	Normal to slightly elevated	Variable

Interpretation of ferritin based on inflammatory status:
Inflammatory Status Ferritin Threshold
No inflammation <30 μg/L
With inflammation <100 μg/L
3
A transferrin saturation of <16% can be used as an alternative threshold for diagnosing iron deficiency anemia, as suggested by the Journal of Crohn's and Colitis guidelines 5
Transferrin saturation <20% has high sensitivity for diagnosing iron deficiency, according to the American Journal of Hematology guidelines 6

Inflammatory Status	Ferritin Threshold
No inflammation	<30 μg/L
With inflammation	<100 μg/L

The preferred dosage of oral iron therapy is ferrous sulfate 200 mg once daily, providing approximately 65 mg of elemental iron, as recommended by the Gut guidelines 7
Ferrous sulfate is the preferred oral iron formulation, administered once daily with vitamin C to enhance absorption, at a standard dose of 200 mg once daily, providing approximately 65 mg elemental iron, as recommended by the American Gastroenterological Association, with a strength of evidence rated as high 2, 8

IV iron is indicated when oral iron is not tolerated, ineffective, or contraindicated, and prefer IV iron formulations that can replace iron deficits with 1-2 infusions, such as Monofer (iron isomaltoside 1000/ferric derisomaltose) and Ferric carboxymaltose (Injectafer), as recommended by the American Gastroenterological Association, with a strength of evidence rated as high 2, 9, 10, 11, 12, 1
Dosing of IV iron is typically based on hemoglobin and body weight, with the following guidelines:
The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines recommend IV iron for CKD patients with anemia when TSAT is ≤30% and ferritin is ≤500 ng/mL, and an increase in hemoglobin is desired without starting ESA treatment 14
IV iron is preferred over oral iron for patients with severe anemia (Hb < 10 g/dL) and advanced CKD (GFR 25 mL/min), as it has shown better efficacy in CKD patients 14
The European Crohn's and Colitis Organization recommends IV iron as first-line therapy for patients with hemoglobin <10 g/dL, as it appears superior to oral iron in patients with inflammatory bowel disease, with a strength of evidence rated as high 2

Regular monitoring of iron status is important in patients with diabetes, especially if they develop chronic kidney disease, as recommended by the American College of Cardiology and Kidney International Supplements guidelines 15, 16
Check hemoglobin response after 3-4 weeks of therapy, which should rise by approximately 2 g/dL, and monitor hemoglobin and red cell indices at 3-month intervals for one year, then after another year, and provide additional iron if hemoglobin or MCV falls below normal, as recommended by the American Gastroenterological Association, with a strength of evidence rated as moderate 8
Complete follow-up iron studies should be done after 8-10 weeks of treatment, and ferritin levels should not be checked too early after intravenous iron administration as they will be falsely elevated, as reported by the American Gastroenterological Association, with a strength of evidence rated as low 17

Risks associated with IV iron therapy include:

Risk	Description
Hypersensitivity reactions	Allergic reactions to IV iron
Infusion reactions	Adverse reactions during IV iron infusion
Iron overload	Excessive iron accumulation with repeated infusions
Hypophosphatemia	Low phosphate levels, particularly with certain formulations

Absolute contraindications for IV iron include known hypersensitivity to any IV iron preparation or components, active systemic infection, and iron overload (ferritin >500 μg/L with transferrin saturation >50%), as recommended by the American Gastroenterological Association, with a strength of evidence rated as high 2

The American Academy of Pediatrics recommends oral iron supplementation at 3-6 mg/kg/day of elemental iron, with a strength of evidence rated as moderate 18
For adult CKD patients not on dialysis, ESA therapy should be initiated when hemoglobin remains below 10 g/dL after initial iron therapy, and the patient has symptoms attributable to anemia (fatigue) 14
The target hemoglobin level for ESA therapy is 10-12 g/dL, and the dose should be adjusted no more frequently than every 4 weeks to avoid exceeding 12 g/dL 14
Inadequate iron repletion should be avoided by ensuring iron stores are replenished before or during ESA therapy to prevent functional iron deficiency 14