Oral iron supplementation guidelines
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Oral Iron Supplementation Guidelines: Dosing Frequency and Amount
Recent research has shifted the approach to oral iron supplementation, especially for iron-deficient women and children. Traditional guidelines recommended daily doses of 150–200 mg elemental iron, often split throughout the day. However, new evidence suggests that lower, less frequent dosing may be more effective and better tolerated. Studies show that doses of 60–120 mg of elemental iron, given as a single morning dose on alternate days, maximize iron absorption and reduce gastrointestinal side effects. This is because higher or more frequent doses increase hepcidin, a hormone that blocks iron absorption, and unabsorbed iron can cause gut irritation and inflammation, leading to poor compliance 14510.
Alternate-Day vs. Daily Iron Supplementation
Multiple studies have compared daily and alternate-day iron supplementation. Alternate-day dosing results in similar or even better improvements in iron stores (serum ferritin) and hemoglobin, with fewer gastrointestinal side effects compared to daily dosing. For example, in iron-depleted women, alternate-day dosing did not result in higher serum ferritin than daily dosing but did reduce iron deficiency at six months and caused fewer side effects . Other trials confirm that alternate-day and single morning dosing optimize iron absorption, while daily or split dosing increases hepcidin and reduces absorption 1510.
Iron Supplementation in Children and Adolescents
For children and adolescents, both frequent (3–7 times per week) and intermittent (1–2 times per week) iron regimens are effective at reducing anemia and iron deficiency. Moderate and high doses are more effective than low doses for improving hemoglobin and ferritin, but the benefits for overall anemia are similar. Shorter durations (1–3 months) are generally as effective as longer durations (7+ months) after adjusting for baseline anemia, except for ferritin, which increases more with longer supplementation . Weekly and shorter-duration iron supplementation at moderate or high doses may be optimal for children at risk of deficiency .
Tolerability and Side Effects
Daily iron supplementation is associated with a higher incidence of gastrointestinal side effects such as abdominal pain, nausea, and changes in stool consistency. These side effects are less common with non-daily (alternate-day or weekly) regimens, which also improve compliance and reduce treatment costs 349.
Monitoring Response and When to Switch to IV Iron
A hemoglobin increase of at least 1.0 g/dL after 14 days of oral iron is a good indicator of a satisfactory response. If this threshold is not met, switching to intravenous iron may be appropriate, as continued oral therapy is unlikely to be effective .
Special Populations and Formulations
For hemodialysis patients with well-controlled inflammation, low-dose oral iron can be effective, especially when serum ferritin is maintained around 60 ng/mL . Newer oral iron formulations, such as ferric maltol and sucrosomial® iron, may offer improved tolerability, but ferrous sulfate remains the most commonly prescribed and cost-effective option 97.
Conclusion
Current evidence supports a shift from traditional daily, split-dose iron supplementation to single morning doses of 60–120 mg elemental iron on alternate days for most adults with iron deficiency or mild anemia. This approach maximizes absorption, minimizes side effects, and improves compliance. For children and adolescents, both frequent and intermittent regimens are effective, with moderate to high doses preferred. Monitoring hemoglobin response after two weeks can help guide further management, including the decision to switch to intravenous iron if needed.
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