Differences Between Ferrous Sulfate Tablets and Iron Chelate Capsules
Ferrous sulfate tablets provide higher elemental iron content per dose but cause more gastrointestinal side effects compared to iron chelate capsules, which offer better tolerability despite lower elemental iron content. 1
Elemental Iron Content and Bioavailability
Ferrous Sulfate
- Standard ferrous sulfate tablets contain 200 mg of ferrous sulfate, providing approximately 65 mg of elemental iron 1
- Considered the gold standard and first-line oral iron therapy for iron deficiency anemia
- Most cost-effective option at approximately £1.00 (or $0.30-$4.50) for a 28-day supply 1
Iron Chelate
- Iron chelate formulations (such as ferrous bisglycinate) typically contain less elemental iron per dose (25-30 mg) 1, 2
- The chelation process binds iron to amino acids (commonly glycine), creating a more stable compound
- Theoretically designed to improve absorption and reduce interaction with food inhibitors 2
Gastrointestinal Tolerability
Ferrous Sulfate
- Associated with significantly higher rates of gastrointestinal side effects including nausea, constipation, diarrhea, and abdominal discomfort 3
- Meta-analysis shows ferrous sulfate increases risk of GI side effects with an odds ratio of 2.32 compared to placebo 3
- Discontinuation rates in clinical practice can reach up to 40% due to side effects 1
Iron Chelate
- Better tolerated with fewer GI side effects 4
- In comparative studies, 37% of patients experienced moderate-to-severe side effects with ferrous sulfate compared to only 21% with iron chelate formulations 4
- May be preferred by patients due to improved tolerability 4
Clinical Efficacy
Ferrous Sulfate
- Well-established efficacy for treating iron deficiency anemia
- Expected to increase hemoglobin by at least 10 g/L after 2 weeks of daily therapy when effective 1
- More rapid iron repletion due to higher elemental iron content per dose 5
Iron Chelate
- Comparable efficacy to ferrous sulfate in some studies 6
- May be less effective in certain populations - one study in gastrectomized patients showed better laboratory parameter improvements with ferrous sulfate 5
- May require longer treatment duration to achieve similar results due to lower elemental iron content 2
Cost Considerations
Ferrous Sulfate
- Most economical option for iron supplementation 1
- Standard ferrous sulfate tablets cost approximately £1.00 for a 28-day supply 1
Iron Chelate
- Generally more expensive than ferrous sulfate 1
- Ferrous bisglycinate typically costs around $2.40 for 30 tablets 1
Administration Recommendations
For both formulations:
- Take on an empty stomach, 1 hour before or 2 hours after meals to maximize absorption 7
- Avoid taking with coffee, tea, calcium supplements, or antacids which can inhibit absorption 1, 7
- Consider taking with vitamin C (500mg) to enhance absorption 7
- Once-daily dosing is preferable due to hepcidin regulation of iron absorption 1, 7
Clinical Decision-Making Algorithm
For initial iron deficiency treatment:
- Start with ferrous sulfate if cost is a concern and patient has no history of GI intolerance
- Choose iron chelate if patient has history of GI sensitivity or previous intolerance to ferrous sulfate
If side effects develop with ferrous sulfate:
Monitor effectiveness:
For long-term maintenance:
- Iron chelate may be preferred for chronic supplementation due to better tolerability
- Ferrous sulfate is more appropriate for rapid correction of significant deficiency
Common Pitfalls to Avoid
- Assuming all iron supplements have similar side effect profiles
- Overlooking the significant impact of GI side effects on adherence
- Failing to recognize that higher elemental iron content doesn't necessarily mean better absorption
- Not considering that food reduces iron absorption by up to 50% 7
- Continuing oral iron despite lack of response after 2 weeks (should consider IV iron instead) 1