Fastest Oral Iron Repletion Strategy
Take 100 mg elemental iron (e.g., one ferrous sulfate 200 mg tablet) once daily in the morning on an empty stomach to achieve the fastest oral iron repletion. 1, 2
Optimal Dosing Regimen
Single morning dose of 50-100 mg elemental iron is the recommended approach, as doses ≥60 mg stimulate hepcidin elevation that persists for 24 hours and blocks subsequent iron absorption 1, 3
Ferrous sulfate 200 mg tablets (providing 65 mg elemental iron) remain the gold standard and most cost-effective option at £1.00 per 28-day supply 1, 2
Taking iron on an empty stomach maximizes absorption, though this may increase gastrointestinal side effects 1, 2
Avoid multiple daily doses, as 60 mg elemental iron taken once daily produces similar overall absorption to 60 mg taken twice daily, with 35-45% reduction in absorption from the second dose due to hepcidin elevation 1, 3
Strategies to Maximize Absorption Speed
Take with vitamin C (250-500 mg) to enhance absorption by forming an iron chelate 2
Avoid tea, coffee, and calcium-containing foods/medications at the time of iron administration, as these significantly inhibit absorption 2
Do not take afternoon or evening doses after a morning dose, as the circadian hepcidin increase is augmented by morning iron and blocks later absorption 3
Expected Response Timeline
Hemoglobin should rise by at least 10 g/L within 2 weeks of starting daily oral iron therapy; failure to achieve this strongly predicts treatment failure (sensitivity 90.1%, specificity 79.3%) 1, 2
Monitor hemoglobin within the first 4 weeks to confirm adequate response 1, 2
Continue treatment for approximately 3 months after hemoglobin normalizes to ensure adequate repletion of marrow iron stores 1, 2
Alternative Dosing if Standard Regimen Not Tolerated
Alternate-day dosing with 100-200 mg elemental iron leads to significantly increased fractional iron absorption compared to daily dosing, though the rate of hemoglobin rise may be slower initially 1, 3
Ferric maltol 30 mg twice daily may be considered for patients with previous intolerance to traditional iron salts, though it costs £47.60 versus £1.00 for ferrous sulfate per 28 days and produces slower iron loading 1, 2
Switching between different ferrous salts (ferrous fumarate, ferrous gluconate) is not supported by evidence for improving tolerability 1
When Oral Iron is Insufficient
Consider parenteral iron when oral iron is contraindicated, ineffective, or not tolerated, or in patients with chronic disease, continuing blood loss, impaired absorption, or gastrointestinal inflammatory pathology 1, 2
Intravenous iron produces clinically meaningful hemoglobin response within one week and can replenish total body iron stores in one or two infusions with modern preparations like ferric carboxymaltose or ferric derisomaltose 1, 2
Common Pitfalls to Avoid
Do not prescribe modified-release preparations, as they are less suitable for prescribing according to the British National Formulary 1, 2
Do not rely on multivitamin preparations, which typically contain insufficient elemental iron (up to 14 mg) for treating iron deficiency 1, 2
Do not continue oral iron indefinitely without monitoring, as failure to respond may indicate non-compliance, malabsorption, continued bleeding, or concurrent vitamin B12/folate deficiency 1