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Abstract: SA-PO687

Intravenous Ferric Carboxymaltose-Induced Severe Hypophosphatemia

Session Information

Category: Fluid, Electrolytes, and Acid-Base Disorders

  • 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical


  • Gul Yousaf Khan, Mohammad, Penn State Health Milton S Hershey Medical Center, Hershey, Pennsylvania, United States
  • Herz Allah, Shatha Ali Mohammad, Penn State Health Milton S Hershey Medical Center, Hershey, Pennsylvania, United States
  • Kaur, Gurwant, Penn State Health Milton S Hershey Medical Center, Hershey, Pennsylvania, United States

Hypophosphatemia (HP) is a rare and severe adverse effect of some intravenous (IV) iron formulations. Here, we present a case of a patient with severe HP after receiving IV ferric carboxymaltose (FCM) due to renal phosphate wasting with high Urine fractional excretion of PO4 (FEP).

Case Description

A 19-year-old female was initially evaluated in the clinic for Iron deficiency due to heavy menstrual bleeding. She received one dose IV FCM because of inability to tolerate oral medications due to gastroparesis. A few days later she had severe generalized bone pains along with weakness, fatigue, nausea, chills, and headache. Labs showed isolated low serum phosphorous (S. PO4) of 1.9 mg/dl (normal 2.5-4.5 mg/dl). She was started on oral potassium-phosphate (K-PO4). Due to persistent HP and symptoms, she was admitted for further management. At the time of admission, labs revealed persistent HP. Remaining serum electrolytes were within normal range. Urine FEP was >55% with high 24-hour PO4 in the urine of 2.305g/24 hours (0.400-1.300). This favored renal PO4 wasting. Fibroblast growth factor (FGF-23) was 58 pg/ml (normal range was <59 pg/ml as per Mayo Clinic lab). She was managed with IV as well as oral PO4 supplements. She was discharged on oral PO4 supplements along with calcitriol. Follow up clinic visit within 1 month showed that her S.PO4 levels normalized to 4 mg/dl. She was able to come off oral PO4 supplementation. This further supports that it was a short-term effect from IV FCM use.


HP has been reported with the use of IV iron preparations, more commonly with IV FCM as compared to other IV formulations. IV FCM induced HP is typically associated with increase in FGF-23 which causes increase in urinary phosphate excretion and suppression of 1,25(OH)2D concentration. Common symptoms include generalized weakness, fatigue, bone, and muscular pain. It is recommended to measure S. PO4 in patients who present with the above-mentioned symptoms. Measuring FEP or TMP/GFR (maximum rate of tubular phosphate reabsorption to the glomerular filtration rate) to confirm intravenous iron-induced renal phosphate wasting has been suggested. Treatment options include activated vitamin D along with phosphate supplements and therapeutic anti-FGF23 antibody.