Recommended Daily Dose of Elemental Iron for Iron Deficiency Anemia
For adult patients with iron deficiency anemia, start with 50-100 mg of elemental iron once daily, taken on an empty stomach—specifically, one ferrous sulfate 200 mg tablet (containing 65 mg elemental iron) is the optimal first-line regimen. 1
Standard Dosing Regimen
The British Society of Gastroenterology strongly recommends one tablet per day of ferrous sulfate, fumarate, or gluconate as initial treatment for iron deficiency anemia. 1
The most practical and cost-effective option is ferrous sulfate 200 mg tablets, which provide 65 mg of elemental iron and cost approximately $1.00 for a 28-day supply. 1, 2
This once-daily dosing is superior to multiple daily doses because oral iron doses ≥60 mg stimulate hepcidin levels that remain elevated for 24-48 hours, blocking subsequent iron absorption by 35-45% and increasing side effects without improving efficacy. 1
Iron should be taken in the morning on an empty stomach to maximize absorption, though this may increase gastrointestinal side effects. 1
Alternative Dosing for Intolerance
If the standard daily dose is not tolerated, reduce to one tablet every other day rather than switching to a different iron salt. 1
Alternate-day dosing with 100-200 mg elemental iron significantly increases fractional iron absorption compared to daily dosing due to hepcidin regulation. 1
The evidence does not support switching between different traditional iron salts (ferrous sulfate, fumarate, gluconate) for intolerance, as this practice lacks supporting data. 1
Alternative options for persistent intolerance include ferric maltol (30 mg twice daily) or parenteral iron. 1
Special Population: Inflammatory Bowel Disease
For patients with inflammatory bowel disease and mild anemia (Hb 11.0-12.9 g/dL in men, 11.0-11.9 g/dL in women) whose disease is clinically inactive, limit elemental iron to no more than 100 mg daily. 1
Parenteral iron should be strongly considered for patients with active inflammatory bowel disease, as luminal iron may exacerbate disease activity and alter intestinal microbiota. 1
Treatment Duration and Monitoring
Monitor hemoglobin response within the first 2-4 weeks of starting treatment—an increase of at least 10 g/L (1 g/dL) after 2 weeks is expected in responding patients. 1
The absence of a hemoglobin rise of at least 10 g/L after 2 weeks strongly predicts treatment failure (sensitivity 90.1%, specificity 79.3%) and warrants reassessment for non-compliance, malabsorption, ongoing bleeding, or alternative diagnoses. 1
Continue oral iron for approximately 3 months after hemoglobin normalizes to ensure adequate repletion of bone marrow iron stores. 1
After iron repletion, monitor blood counts every 6 months initially to detect recurrent iron deficiency anemia. 1
What NOT to Do
Do not prescribe multiple daily doses of iron (e.g., twice or three times daily)—this increases side effects without improving absorption due to hepcidin-mediated blockade. 1
Do not use modified-release iron preparations, as they release iron beyond the duodenum where absorption is optimal and are not supported by evidence. 1
Avoid taking iron with food, tea, coffee, or calcium-containing products, as these reduce iron absorption by up to 50%. 1
Do not use multivitamin preparations as the sole iron source, as they contain insufficient elemental iron (typically ≤14 mg). 1
When to Consider Parenteral Iron
Parenteral iron should be considered when oral iron is contraindicated, ineffective after an adequate trial, or not tolerated despite dose modifications. 1
For parenteral iron, ferric carboxymaltose or ferric derisomaltose can deliver 500-1000 mg in a single 15-30 minute infusion without requiring a test dose. 1
The total iron deficit can be calculated using the Ganzoni formula, or an empiric dose of 1000 mg can be administered with interval reassessment. 1
Common Pitfalls to Avoid
Do not defer iron replacement therapy while awaiting diagnostic investigations unless colonoscopy is imminent. 1
Do not assume that switching between different ferrous salts will improve tolerability—the evidence does not support this common practice. 1
Do not overlook the need for continued monitoring after hemoglobin normalization, as recurrent anemia may indicate persistent disease activity even when inflammatory markers appear normal. 1
Remember that packed red cell transfusion should be reserved for severe symptomatic anemia or hemodynamic instability, as each unit contains only 200 mg of elemental iron and will not replenish iron stores. 1