Recommended Daily Iron Dose for Mild Iron-Deficiency Anemia
For a healthy non-pregnant adult with mild iron-deficiency anemia, take 50–100 mg of elemental iron once daily in the morning on an empty stomach, using ferrous sulfate as the first-line formulation. 1
First-Line Oral Iron Therapy
Ferrous sulfate (200 mg tablet = 65 mg elemental iron) is the gold-standard formulation because it is the most cost-effective option (approximately £1.00 per 28-day supply) and no oral iron formulation has demonstrated superior efficacy or tolerability over another. 1
Once-daily dosing of 50–100 mg elemental iron is superior to multiple daily doses because doses ≥60 mg trigger hepcidin elevation that persists for 24 hours, blocking absorption of subsequent doses by 35–45%. 1
Take iron on an empty stomach in the morning to maximize absorption, though this may increase gastrointestinal side effects. 1
Alternative Ferrous Salts (If Ferrous Sulfate Not Tolerated)
- Ferrous fumarate (322 mg tablet = 106 mg elemental iron) or ferrous gluconate (300 mg tablet = 37 mg elemental iron) may be substituted, although evidence does not support improved tolerability when switching between different ferrous salts. 1, 2
Strategies to Improve Absorption and Tolerability
Taking iron with 250–500 mg vitamin C enhances absorption by forming a chelate with iron. 1
Avoid taking iron with tea, coffee, or calcium-containing foods/medications, which inhibit absorption. 1
If standard daily dosing causes intolerable gastrointestinal side effects, switch to alternate-day dosing (every other day) with 100–200 mg elemental iron, which markedly increases fractional iron absorption and reduces side effects while maintaining efficacy. 1, 3
Monitoring Treatment Response
Check hemoglobin at 2 weeks: an increase of ≥10 g/L strongly predicts treatment success (sensitivity 90.1%, specificity 79.3%). 1, 2
Continue monitoring hemoglobin every 4 weeks until normalization, then continue treatment for an additional 3 months after hemoglobin normalizes to replenish iron stores. 1, 2
Failure to achieve ≥10 g/L rise at 2 weeks warrants investigation for non-compliance, continued blood loss, malabsorption, or concurrent vitamin B12/folate deficiency. 1
Formulations to Avoid
Do not prescribe modified-release iron preparations, as they release iron beyond the duodenum (the primary absorption site) and are classified as "less suitable for prescribing" by the British National Formulary. 1
Do not rely on multivitamin preparations (typically containing ≤14 mg elemental iron) as the sole iron source for treating iron-deficiency anemia. 1
When to Escalate to Intravenous Iron
Consider IV iron when oral iron is not tolerated despite modifications, ferritin levels do not improve after an adequate oral trial, or the patient has conditions impairing oral iron absorption (e.g., inflammatory bowel disease, post-bariatric surgery, celiac disease). 1, 2
IV iron produces a clinically meaningful hemoglobin response within one week and can replenish total body iron stores in one or two infusions using modern formulations such as ferric carboxymaltose (750 mg IV twice, ≥7 days apart) or ferric derisomaltose. 1, 2
Common Pitfalls to Avoid
Do not prescribe multiple daily doses of iron, as this increases gastrointestinal side effects without improving hemoglobin response due to hepcidin-mediated blockade of absorption. 1
Do not continue oral iron indefinitely without monitoring, as failure to respond may indicate the need for IV iron or investigation of underlying causes. 1
Do not switch between different ferrous salts expecting better tolerability, as this is not supported by evidence. 1