What are the contraindications to oral iron tablets?

Oral Iron Tablet Contraindications

Oral iron supplementation is absolutely contraindicated in patients with hemochromatosis and other iron overload disorders, and should not be given to patients with normal or elevated ferritin levels, as this can cause tissue damage to the liver, heart, and pancreas. 1

Absolute Contraindications

• Hemochromatosis and iron overload disorders – Iron supplementation exacerbates these conditions and increases the risk of organ damage 1
• Normal or elevated ferritin levels – Supplementation is potentially harmful and provides no therapeutic benefit 1
• Anemia not attributed to iron deficiency – Oral iron should be avoided when anemia has other causes 2

Relative Contraindications and Precautions

• Active infection – Iron may promote bacterial growth and should not be given during active infectious processes 1
• Severe anemia with hemoglobin <100 g/L – Particularly in patients with malabsorption conditions (inflammatory bowel disease, celiac disease, post-bariatric surgery), where oral iron is poorly absorbed and intravenous iron should be considered first-line 2
• Early pregnancy – While not an absolute contraindication to oral iron, caution is warranted as early pregnancy is a contraindication to intravenous iron formulations 1

Clinical Situations Requiring Alternative Approaches

• Inflammatory conditions – Patients with active inflammatory bowel disease, chronic kidney disease, or chronic heart failure often have functional iron deficiency with elevated hepcidin that blocks oral iron absorption 2
• Malabsorption syndromes – Conditions such as celiac disease, Crohn's disease, or prior gastric surgery significantly impair oral iron absorption, making intravenous iron more appropriate 2
• Intolerance to oral iron – When gastrointestinal side effects (nausea, constipation, diarrhea, abdominal discomfort) are severe enough to prevent adherence, intravenous iron should be considered 2

Safety Thresholds That Mandate Discontinuation

• Transferrin saturation >50% – Further oral iron supplementation offers no benefit and raises the risk of iron overload 1
• Serum ferritin >500 mg/L (or >800 µg/L in some guidelines) – Continuing iron beyond these levels is potentially harmful 2, 1

Important Monitoring Considerations

• Iron parameters can be misleading in inflammation – Ferritin is an acute-phase reactant and may be falsely elevated in inflammatory states, requiring careful assessment before withholding iron 1
• Hypersensitivity to oral iron salts – While rare, documented hypersensitivity reactions to oral iron preparations exist and constitute a contraindication to that specific formulation, though desensitization protocols have been successfully used 3, 4

Common Pitfalls to Avoid

• Do not assume all patients with low hemoglobin need iron – Always confirm iron deficiency with appropriate laboratory studies (ferritin, transferrin saturation, serum iron) before starting supplementation 2
• Do not continue oral iron indefinitely without monitoring – Check hemoglobin and iron parameters at 4 weeks; if no response occurs after 2-4 weeks of adherent therapy, oral iron has failed and intravenous iron should be considered 2
• Do not use oral iron in patients with ongoing blood loss exceeding absorption capacity – These patients require intravenous iron to achieve adequate repletion 2