Iron Deficiency Anaemia in Acute Care

This is an abbreviated version of the full GGC guideline Iron Deficiency Anaemia in Adults: Oral and Intravenous Iron Therapy Treatment.

The guideline does not cover the diagnosis or treatment in the following clinical situations:

  • Pregnancy
  • Postpartum anaemia
  • Surgery / trauma
  • Paediatrics (<16 years)
  • Patients with chronic kidney disease (CKD) stages 4–5.


Iron deficiency anaemia (IDA) occurs in more severe stages of iron deficiency, when the body is iron deficient to the degree that red blood cell and haemoglobin (Hb) production is reduced. The cause of IDA is often multifactorial, and can be broadly attributed to:

  • Dietary deficiency
  • Malabsorption e.g. coeliac disease, gastrectomy, Helicobacter pylori infection
  • Increased loss - chronic blood loss, especially from the uterus or gastrointestinal tract
  • Increased requirement
  • Other causes e.g. blood donation, self-harm, haematuria, medication.

Assessment and monitoring

For diagnosis of IDA, see flowchart.

Serum ferritin (SF):

  • Most useful test in confirming the diagnosis of IDA;
  • A low SF (<15micrograms/L) provides absolute evidence of iron deficiency;
  • Can be elevated by inflammatory processes and can mask iron deficiency;
  • A SF >100micrograms/L generally rules out IDA even in the presence of inflammatory disease;
  • If the results are equivocal, practitioners should consider monitoring the Hb concentration in response to a trial of oral iron.

For further information on the interpretation of iron studies, please refer to the Medicines Update blog article, search for 'Diagnosis of IDA - Iron Studies'.

Drug therapy / treatment options

Treatment with iron replacement therapy should be considered for patients with clinically relevant IDA in whom the clinical benefit of treatment outweighs any risk. Investigation and treatment of an underlying cause should prevent further iron loss, but all patients should have iron supplementation both to correct anaemia and replenish body stores.

Oral iron (first-line treatment choice)

Give ferrous fumarate oral 210mg or ferrous sulphate 200mg once a day.

The optimal dose of oral iron-replacement therapy for adults with IDA is not clearly defined. Traditionally oral iron salts were taken as a split dose, two or three times a day (100mg/200mg elemental iron daily). More recent data suggest that lower doses and more infrequent administration may be just as effective and likely to be associated with lower rate of adverse effects.

Hb levels should rise by at least 20g/L over 3-4 weeks. Treatment should be continued for 3 months after Hb is optimised and then stopped.

If response is poor, consider:

  • Non-compliance*- assess and address adverse effects
  • Continued blood loss with inadequate replacement of iron - investigate and treat underlying cause(s)
  • Malabsorption
  • Wrong diagnosis - re-check ferritin and reassess
  • Other complicating factors, in which case reassess treatment.

*If oral iron treatment is not tolerated, adverse effects should be addressed by:

  • Reducing the dose frequency to once a day if prescribed iron two to three times day, or to one tablet on alternate days if prescribed iron once a day.
  • Taking with or after food (note doing so decreases absorption by up to 75%).
  • Trying an alternative salt / formulation with a lower content of elemental iron. See the elemental content of different oral iron preparations here.

Drug interactions

Iron salts are not well absorbed orally and their absorption is reduced if taken concurrently with certain foods/drugs/supplements such as:

  • Milk and dairy products
  • Tannins (present in tea, coffee, cocoa)
  • Phytates (present in cereal grains, legumes, nuts and seeds)
  • Calcium, zinc or magnesium salts (e.g. in antacids or supplements)

Oral iron can reduce the absorption of some drugs if taken concurrently (including tetracyclines, quinolones and bisphosphonates) reducing bioavailability and clinical effect. A suitable interval to separate administration is advised (See Medicines Update blog, search for 'Warning- Antibiotic treatment risk failure', for information on the management of these interactions). 

Intravenous iron (second-line treatment choice)

This does not produce a faster Hb response than oral iron, provided that the oral iron preparation is taken reliably and is absorbed adequately. It may produce severe adverse effects, and should be reserved for patients who meet the inclusion criteria below.

Inclusion criteria

  • Genuine intolerance to oral iron preparations. Iron preparations with a low content of elemental iron must be tried (with food) before acceptance of genuine intolerance to oral iron.
  • Severe IDA and concern regarding the patient's ability to comply with oral iron treatment.
  • Patients with clinically active inflammatory bowel disease (IBD), with previous intolerance to oral iron, with haemoglobin <100g/L, and in patients who need erythropoiesis-stimulating agents.
  • Patients with heart failure (HF) with reduced ejection fraction, New York Heart Association (NYHA) class III with a left ventricular ejection fraction (LVEF) ≤45%, or NYHA class II, LVEF 40%, who have a Hb level of 95 to 135g/L and iron deficiency (defined as ferritin <100micrograms/L or <300micrograms/L if transferrin saturation (TSAT) <20%).

Intravenous iron therapy should be initiated by a consultant, specialist trainee or equivalent. Some services may delegate responsibility to nominated non-medical prescribers.

There can be complications with IV iron. See below for details. Administration should only occur during working hours when adequate supervision is available. 

Choice of IV iron agent

A guide to help with product selection based on patient characteristics can be found here, alternatively consider prescribing the most familiar product within your clinical area. See the individual dosing and administration guides for Ferinject® (ferric carboxymaltose) or Monofer® (ferric derisomaltose). 

Note: These guides should be printed for use as prescribing and administration checklists in clinical areas. These can be printed from the links above.

Interaction with oral iron preparations

  • Combined treatment with oral and IV iron may lead to the appearance of highly toxic non-transferrin bound iron.
  • It is recommended that oral iron preparations are discontinued at least 48 hours prior to IV iron infusions.
  • The need for oral iron therapy should be reviewed following IV replacement and generally should not be required.
  • If ongoing prophylaxis is deemed necessary, oral iron should not be restarted for at least 5 days after the last IV iron infusion

Intravenous iron- complications

Hypersensitivity reactions

These include serious and potentially fatal anaphylactic / anaphylactoid reactions. Caution is needed with every dose of IV iron that is given, even if previous administrations have been well tolerated. The steps outlined in the administration checklists for Ferinject® (ferric carboxymaltose) or Monofer® (ferric derisomaltose) should be taken to monitor patients during and for at least 30 minutes after every administration. If hypersensitivity reactions or signs of intolerance occur, the infusion must be stopped immediately and appropriate management initiated. A guide to the management of hypersensitivity reactions during the administration of IV iron can be found here (link active on website only).


Paravenous leakage at the infusion site may lead to irritation and potentially long lasting or permanent brown discolouration at the site of infusion. Patients should be informed about the possibility of discolouration and advised to report any signs of irritation or pain at the infusion site immediately. The most effective safeguard against extravasation is to visually inspect the infusion site regularly. The steps outlined in the checklists for Ferinject® (ferric carboxymaltose) or Monofer® (ferric derisomaltose) should be taken to monitor the infusion site during and for at least 30 minutes following administration. In case of suspected paravenous leakage, treatment requires prompt attention as outlined here

Intravenous iron - assessing response

Hb and ferritin levels should be rechecked to assess response to IV iron treatment. These should be assessed no earlier than 4 weeks following treatment. Hb levels should rise by at least 20g/L over 4 weeks.

Intravenous iron – communication of treatment

Treatment with IV iron should be clearly communicated with the patient’s GP and other healthcare professionals. This could be via a discharge letter or outpatient clinic letter. It should include details of the treatment received and clearly state arrangements in place for follow up blood monitoring.


Guideline reviewed: September 2022

Page last updated: December 2023