Synopsis
Choose oral or intravenous iron for the confirmed indication, prescribe a formulation-specific regimen, manage intolerance and interactions, and verify response, replenishment and infusion safety.
- Confirm iron deficiency or a guideline-supported functional iron indication before treatment. Low haemoglobin alone does not justify iron when haemolysis, B12 deficiency, renal disease or marrow pathology may dominate.
- For most stable adults, BSG prefers one tablet daily of ferrous sulfate, fumarate or gluconate; if intolerance occurs, every-other-day dosing is a supported alternative before abandoning oral therapy.
- The iron salt and elemental iron content are not interchangeable. Prescribe the exact product and tablet strength and check the BNF rather than writing 'iron tablets'.
- Absorption is reduced by food and several medicines, but fasting administration can worsen intolerance. Agree a workable regimen and separate interacting treatments using current BNF advice.
- Choose intravenous iron when oral treatment is ineffective, not tolerated, not absorbed, contraindicated or too slow for the clinical need; calculate total requirement using that product's SmPC.
- Intravenous formulations differ in maximum single dose, dilution, infusion rate and repeat interval. Never transfer instructions between ferric carboxymaltose, ferric derisomaltose and iron sucrose.
- All intravenous products can cause hypersensitivity and extravasation. Give them where trained staff can monitor the patient and manage anaphylaxis, and observe for at least 30 minutes after each administration.
- Repeated or high-dose ferric carboxymaltose can cause clinically important hypophosphataemia and osteomalacia; identify risk, monitor phosphate where advised and reconsider the formulation if persistent.
Key red flags
Flushing, urticaria, wheeze, airway swelling, hypotension or collapse during infusion requires immediate cessation, ABCDE assessment and the anaphylaxis pathway.
Investigation priorities
Confirm indication, severity and inflammatory modification before treatment.
Management branches
Confirmed iron deficiency is stable and oral absorption is expected to be adequate.
- Preferred treatment is one daily tablet of ferrous sulfate, fumarate or gluconate with the exact product documented, plus counselling on adverse effects, food and medicine interactions and child-safe storage.
- If intolerance occurs, the supported alternative is one tablet every other day, another salt or a carefully agreed food schedule rather than unstructured dose escalation.
- Check an early haemoglobin response and continue after normalisation to replenish stores; escalate absent response to a cause and route review.
Key medicines
Ferrous sulfateOne 200 mg tablet by mouth once daily is a common adult BSG starting regimen; reduce to every other day if gastrointestinal intolerance limits adherence.Common effects are nausea, abdominal discomfort, constipation, diarrhoea and dark stools. Check BNF spacing from interacting medicines, avoid overdose in children and investigate persistent non-response or bleeding.
Ferrous fumarateOne 210 mg tablet by mouth once daily is a BSG-listed alternative, with every-other-day administration if needed for tolerance.Gastrointestinal effects and interactions are similar to other oral salts. Verify tablet strength because formulations differ and do not prescribe by salt name without dose.