Oral Iron Therapy for Adult Iron‑Deficiency Anemia – Evidence‑Based Recommendations

Dosing Strategy

Initiate therapy with 50–100 mg elemental iron once daily (e.g., one ferrous‑sulfate 200 mg tablet providing ~65 mg elemental iron) on an empty stomach; alternate‑day dosing is preferred over consecutive daily dosing because it yields higher fractional absorption and reduces hepcidin‑mediated inhibition【1】【2】【3】.
Ferrous sulfate is the formulation of choice for cost‑effectiveness【1】【5】; ferrous fumarate (≈70–106 mg elemental iron/tablet) and ferrous gluconate (≈37 mg elemental iron/tablet) are acceptable alternatives【1】【6】.
Oral iron doses ≥60 mg elemental iron trigger a hepcidin rise that persists for ~24 h, diminishing absorption of subsequent doses; this supports the alternate‑day schedule【3】【2】【7】.

Administer the dose in the morning on an empty stomach to maximize absorption before the circadian increase in hepcidin【8】【9】.
Add vitamin C (100–250 mg) to the iron dose (e.g., with orange juice) to enhance absorption【5】.

Assess hemoglobin response within the first 4 weeks of therapy; a rise of ≥10 g/L after 2 weeks indicates adequate response【3】【2】【4】【6】【8】.
Lack of this early rise predicts treatment failure (sensitivity ≈ 90 %, specificity ≈ 79 %)【6】【8】.
Continue oral iron for ~3 months after hemoglobin normalization to replenish bone‑marrow iron stores【1】【3】【2】【10】【11】; in healthy individuals, 2 months may be sufficient【8】【9】.
Post‑treatment follow‑up: check full blood counts every 6 months initially, then every 3 months during the first year and every 6 months for the next 2–3 years【1】【3】【9】.

If standard dosing causes gastrointestinal side effects, reduce to one tablet every other day; this regimen lowers GI adverse events (relative risk ≈ 0.56 in pregnant women) and reduces nausea prevalence【2】【4】【11】【8】【9】【6】.
Ferric maltol (30 mg twice daily) is an alternative for patients with inflammatory bowel disease or intolerance to traditional ferrous salts【1】【3】【7】.
Switching between different ferrous salts is not supported by evidence【8】【9】.

Switch to IV iron when oral iron is contraindicated, ineffective, or not tolerated; when there is no hemoglobin rise after 2 weeks of adequate oral therapy; in the presence of malabsorption syndromes; or when ongoing blood loss exceeds the replacement capacity of oral iron【3】【2】【4】【11】【8】【12】.

Do not prescribe modified‑release iron preparations, as they release iron beyond the duodenum where absorption is optimal【1】【6】.
Avoid split dosing throughout the day; a single morning dose maximizes absorption and minimizes hepcidin‑mediated inhibition【5】.
Do not delay iron therapy while awaiting diagnostic investigations; start treatment promptly unless an imminent colonoscopy necessitates temporary postponement【2】【4】.