Ferrous Fumarate vs. Ferrous Sulfate for Iron Deficiency Anemia
Ferrous fumarate is equally effective as ferrous sulfate for treating iron deficiency anemia, but ferrous sulfate remains the preferred first-line agent due to its lower cost and extensive evidence base. 1
Comparative Efficacy
No single oral iron formulation has demonstrated superiority over another in terms of clinical efficacy. 1 All ferrous salts (sulfate, fumarate, gluconate) are equally effective at correcting hemoglobin levels and replenishing iron stores when equivalent doses of elemental iron are administered. 1
The British Society of Gastroenterology guidelines explicitly state that ferrous sulfate, ferrous fumarate, and ferrous gluconate are all equally effective for treating iron deficiency anemia. 1
A 2012 systematic review confirmed that ferrous sulfate preparations remain the established standard treatment given their good bioavailability, efficacy, and acceptable tolerability demonstrated in large clinical studies. 2
Why Ferrous Sulfate is Preferred
Ferrous sulfate is recommended as the first-line oral iron formulation solely because it is the least expensive option. 1 The American Gastroenterological Association's 2024 clinical practice update explicitly states this cost-based preference, noting that no formulation has advantages over another from an efficacy standpoint. 1
The initial treatment should be one tablet per day of ferrous sulfate, fumarate, or gluconate. 1
Most clinical studies establishing the evidence base for oral iron therapy used ferrous sulfate, making it the reference standard. 1
Practical Dosing Considerations
Start with 50-100 mg elemental iron once daily (e.g., one ferrous sulfate 200 mg tablet containing approximately 65 mg elemental iron). 1 This lower dose may optimize absorption while minimizing gastrointestinal side effects.
Once-daily or alternate-day dosing is as effective as traditional three-times-daily regimens and improves tolerability and compliance. 1 Alternate-day dosing may be better tolerated with similar iron absorption rates. 1
No more than 100 mg elemental iron per day is recommended, particularly in patients with inflammatory bowel disease. 1
When to Switch Formulations
If ferrous sulfate is not tolerated, switching to ferrous fumarate or ferrous gluconate is reasonable. 1 However, the standard practice of switching between different ferrous salts is not strongly supported by evidence. 1
Alternative formulations (liquid preparations, different salts) may be better tolerated when tablets are not. 1
Consider adding vitamin C (250-500 mg) to enhance iron absorption if response is suboptimal. 1
Monitoring Response
Monitor hemoglobin after 2 weeks of treatment. Failure to achieve at least a 10 g/L rise in hemoglobin is strongly predictive of subsequent treatment failure (sensitivity 90.1%, specificity 79.3%). 1
Continue monitoring every 4 weeks until hemoglobin normalizes. 1
Continue oral iron for 2-3 months after hemoglobin normalization to replenish iron stores. 1
When Oral Iron Fails
Intravenous iron should be used if the patient does not tolerate oral iron, ferritin levels do not improve with a trial of oral iron, or the patient has conditions where oral iron is unlikely to be absorbed (active inflammatory bowel disease, hemoglobin <10 g/dL, malabsorption syndromes). 1
Parenteral iron should only be considered after intolerance to at least two different oral preparations. 1