Iron Deficiency Anemia Treatment with Ferrous Sulfate

Recommended Dosing Strategy

The British Society of Gastroenterology recommends taking ferrous sulfate 325 mg (65 mg elemental iron) once daily for the treatment of iron deficiency anemia, as this dosing is as effective as multiple daily doses while improving tolerability 1
For patients with moderate to severe anemia requiring faster correction, 50-100 mg elemental iron daily remains appropriate 1
For patients experiencing gastrointestinal side effects, consider alternate-day dosing, which leads to significantly increased fractional iron absorption compared to daily dosing 1
For patients on erythropoietin therapy, higher doses up to 325 mg three times daily (195 mg elemental iron total) may be needed 4, 5, 6

The British Society of Gastroenterology guidelines represent the most recent high-quality evidence and recommend once-daily dosing as standard practice, as iron absorption triggers hepcidin production, which blocks further iron absorption for approximately 24 hours 1
Taking iron more frequently than once daily provides diminishing returns, as hepcidin levels are stimulated by 60 mg elemental iron taken once daily, reducing subsequent iron absorption by 35-45% when taken more frequently 1

Expect hemoglobin to rise by at least 10 g/L within 2 weeks of starting daily oral iron therapy, and absence of this rise strongly predicts subsequent treatment failure 3
Ferritin levels should increase within one month in adherent patients 7
Do not prescribe modified-release preparations, as iron is released beyond the duodenum and proximal jejunum where absorption is optimal 1
Avoid concurrent intake with absorption inhibitors, such as dairy products, tea, coffee, or calcium-containing foods, as these significantly reduce absorption 7

Ferrous sulfate 325 mg once daily is generally well-tolerated, and in a randomized trial, ferrous sulfate was associated with less diarrhea and superior efficacy compared to iron polysaccharide complex 1