Ferrous Bisglycinate Dosage for Iron Deficiency Anemia
For adults with iron deficiency anemia, ferrous bisglycinate should be dosed at 25 mg of elemental iron once daily, which provides equivalent efficacy to standard ferrous sulfate 50-65 mg daily while causing fewer gastrointestinal side effects. 1, 2
Adult Dosing
- Standard dose: 25 mg elemental iron once daily 1, 3, 2
- This lower dose of ferrous bisglycinate (25 mg) is as effective as ferrous sulfate 50 mg in preventing and treating iron deficiency anemia 2
- The FDA-approved dosing is one tablet daily or as directed by a physician 3
- Take in the fasting state for optimal absorption, consistent with general oral iron recommendations 4
Pediatric Dosing
- For infants and young children: 5 mg/kg/day of elemental iron 5
- This dosing has demonstrated 90.9% apparent iron bioavailability compared to 26.7% for ferrous sulfate 5
- In school-aged children, 30 mg/day of elemental iron as ferrous bisglycinate chelate effectively increases ferritin concentrations 6
Key Advantages Over Traditional Iron Salts
Ferrous bisglycinate offers superior tolerability with comparable or better efficacy:
- Significantly fewer gastrointestinal complaints compared to ferrous sulfate 50 mg or ferrous fumarate 40 mg 7, 2
- Lower frequency of black stools (8% vs 22-31% with other formulations) 7
- Higher bioavailability allows for lower elemental iron dosing 5
- Sustained ferritin increases at 6 months post-supplementation 6
Monitoring and Duration
- Check hemoglobin response within 2-4 weeks of initiating therapy; expect at least 10 g/L increase within 2 weeks 4
- Continue treatment for 3 months after hemoglobin normalization to replenish iron stores 4
- Monitor hemoglobin every 4 weeks until normalized 4
When to Consider Alternative Therapy
Switch to intravenous iron if:
- No hemoglobin increase of at least 10 g/L after 2 weeks of adherent oral therapy 4
- Ferritin fails to increase after 1 month of treatment 1
- Patient has malabsorption (post-bariatric surgery, inflammatory bowel disease) 1
- Ongoing blood loss exceeds oral iron absorption capacity 1
Important Caveats
- Avoid tea and coffee within 1 hour of iron administration as they powerfully inhibit absorption 1
- The general recommendation for oral iron is 50-100 mg elemental iron daily, but ferrous bisglycinate achieves this with only 25 mg due to superior bioavailability 4, 2
- While ferrous bisglycinate 18 mg was found non-inferior to ferrous sulfate 60 mg in one study of iron-replete women, the 25 mg dose remains the evidence-based standard for treating iron deficiency 8, 2
- Cost is approximately $2.40 per 30 tablets, making it more expensive than ferrous sulfate but significantly less expensive than parenteral iron 1