Iron Infusions and Hypophosphataemia

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Iron deficiency anaemia is a common condition that can have a significant impact on a patient’s quality of life. The incidence of iron deficiency anaemia in Australia is estimated to be 12% in non-pregnant and up to 15% of pregnant females.1 Iron deficiency without anaemia may be up to three times more common but is often undiagnosed.2

Associate Professor Chris Barnes
Associate Professor Chris Barnes is the National Director of Clinical Pathology and provides strategic direction nationally for haematology at Clinical Labs. He is a clinical and laboratory-trained haematologist who has worked with Melbourne Hematology and Clinical Labs (and previously Healthscope) for several years. A/Prof Barnes also works at the Royal Children’s Hospital and is director of the Haemophilia Treatment Centre. He has experience in both management and leadership positions. A/Prof Barnes has an active clinical research interest and is also the director of Melbourne Haematology (Clinical) and Melbourne Paediatric Specialists.

While oral iron therapy is often the first-line treatment, some patients are unable to tolerate it due to gastrointestinal side effects or poor absorption.3 In these cases, iron infusions may be a suitable alternative.

A common iron infusion therapy in Australia is ferric carboxymaltose (FCM). FCM is a complex of iron and carbohydrate that is administered intravenously and has been shown to be safe and effective in treating iron deficiency anaemia in patients who are unable to tolerate oral iron therapy.4

However, there have been reports of symptomatic hypophosphatemia associated with FCM use. This is a rare condition where the levels of phosphate in the blood are abnormally low, which can cause a range of symptoms including weakness, fatigue, and bone pain. It is thought to occur due to the rapid increase in fibroblast growth factor 23 (FGF23) which increases phosphate secretion. Prolonged hypophosphatemia and associated secondary hyperparathyroidism may be a risk factor for metabolic bone disease, including the development of ostemalacia.

To help manage this potential risk, doctors may consider monitoring serum phosphate, calcium, vitamin D, and parathyroid hormone (PTH) levels in patients who present with symptoms following FCM infusions. If symptomatic hypophosphatemia occurs, treatment may include phosphate and vitamin D supplementation, along with discontinuation of FCM use.

Despite this potential risk, iron infusions with FCM can offer significant benefits for patients who are unable to tolerate oral iron therapy. By restoring iron levels in the body, patients may experience improved energy levels and improved quality of life. Clinical review and laboratory monitoring for side effects are recommended in patients who present with concerning symptoms following iron infusion. 


  1. Pasricha S-RS, Flecknoe-Brown SC, Allen KJ, Gibson PR, McMahon LP, Olynyk JK, et al. Diagnosis and management of iron deficiency anaemia: a clinical update. Medical Journal of Australia. 2010;193(9):525-32.
  2. Ioannou GN, Rockey DC, Bryson CL, Weiss NS. Iron deficiency and gastrointestinal malignancy: a population-based cohort study. Am J Med. 2002;113(4):276-80.
  3. Tolkien Z, Stecher L, Mander AP, Pereira DIA, Powell JJ. Ferrous sulfate supplementation causes significant gastrointestinal side-effects in adults: a systematic review and meta-analysis. PLoS One. 2015;10(2):e0117383-e.
  4. Bailie GR. Efficacy and safety of ferric carboxymaltose in correcting iron-deficiency anemia: a review of randomized controlled trials across different indications. Arzneimittelforschung. 2010;60(6a):386-98.

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