From the Guidelines
The best oral treatment for iron deficiency anemia is ferrous sulfate, as it is the least expensive iron formulation with no advantages of other formulations over it, as stated in the 2024 study by the American Gastroenterological Association 1.
Key Considerations
- The dose of ferrous sulfate can vary, but a common recommendation is 325 mg (containing 65 mg elemental iron) taken 2-3 times daily between meals, as seen in various studies 1.
- For optimal absorption, ferrous sulfate should be taken with vitamin C-containing foods or beverages and separated from calcium, antacids, tea, coffee, and dairy products by at least 2 hours.
- Treatment should continue for 3-6 months after hemoglobin normalizes to replenish iron stores.
- Side effects include gastrointestinal distress (constipation, nausea, abdominal pain), which can be managed by starting with a lower dose and gradually increasing, taking with food (though this reduces absorption), or switching to alternative formulations like ferrous gluconate or ferrous fumarate.
Important Notes
- Stool darkening is expected and harmless.
- Ferrous sulfate is preferred due to its high elemental iron content, good bioavailability, and low cost.
- Iron supplementation works by providing the essential component needed for hemoglobin synthesis, allowing for increased red blood cell production and oxygen-carrying capacity in the blood.
- The optimal duration of treatment and the best measure of true iron repletion are unclear, but regular hemoglobin monitoring is recommended to ensure a satisfactory response 1.
From the FDA Drug Label
Each tablet contains 324 mg of ferrous gluconate, equivalent to 38 mg of elemental iron, providing 211% of the U.S. recommended daily intake (RDI) of iron for adults and children 4 and older. Adult Serving Size: 1 tablet three to four times daily. CONTAINS: Each tablet contains 324 mg of ferrous sulfate, equivalent to 65 mg of elemental iron, providing 362% of the U.S. recommended daily intake (RDI) of iron for adults and children 4 and older.
The best PO option to treat iron deficiency anemia is ferrous sulfate due to its higher elemental iron content (65 mg per tablet) compared to ferrous gluconate (38 mg per tablet). The recommended dose for ferrous sulfate is not explicitly stated in the provided label, but for ferrous gluconate, the adult serving size is 1 tablet three to four times daily 2. Since the dose for ferrous sulfate is not provided, a conservative clinical decision would be to consult the physician for the appropriate dosage of ferrous sulfate 3.
From the Research
Oral Iron Supplementation Options
- Ferrous sulfate is the most commonly prescribed oral iron supplement, but other ferrous salts and ferric complexes are also widely used 4.
- Novel iron formulations, such as ferric maltol and nanoparticle encapsulated sucrosomial iron, have been developed in recent years 4.
- High-dose carbonyl iron has been shown to be well-tolerated and effective in treating iron deficiency anemia, with a mean 1.5-fold increase in estimated iron absorption 5.
Dosage and Efficacy
- A study comparing ferrous sulfate and iron polysaccharide complex found that ferrous sulfate resulted in a greater increase in hemoglobin concentration at 12 weeks, with a dose of 3 mg/kg of elemental iron once daily 6.
- Another study found that four commonly prescribed oral iron preparations (ferrous sulfate, ferrous fumarate, ferrous ascorbate, and carbonyl iron) were equally effective in improving hemoglobin concentration and other hematological parameters at a dose of 200 mg elemental iron per day 7.
- The optimal dosage and frequency of oral iron supplements may vary depending on the individual patient and the specific formulation used 4.
Comparison with Intravenous Iron Therapy
- A study comparing oral iron therapy with intravenous iron therapy found that intravenous iron therapy was more effective in increasing hemoglobin and serum ferritin levels, but had a higher incidence of adverse effects such as arthralgia and hypotension 8.
- Intravenous iron therapy may be considered for patients who are unable to tolerate oral iron supplements or who require rapid correction of iron deficiency anemia 8.