Injectafer (ferric carboxymaltose): Boxed Warning added for hypophosphataemia risk
FDA added a Boxed Warning — the agency's strongest label caution — to Injectafer (ferric carboxymaltose injection) to describe the risk of severe and symptomatic low phosphate levels. Clinicians are advised to check serum phosphate before and after infusion in patients at risk.
On 1 September 2026 FDA added a Boxed Warning ↗ — the agency's strongest caution — to Injectafer (ferric carboxymaltose injection) to describe the risk of severe and symptomatic hypophosphataemia (low phosphate levels). This warning applies to all approved intravenous iron formulations containing ferric carboxymaltose.
About hypophosphataemia with ferric carboxymaltose
Ferric carboxymaltose is known to suppress fibroblast growth factor 23 (FGF-23) ↗, which in turn inhibits tubular phosphate reabsorption. This can cause serum phosphate to fall below 2.0 mg/dL in a substantial proportion of patients — sometimes severely (< 1.0 mg/dL). Symptoms include fatigue, muscle weakness, bone pain, and in severe cases respiratory failure. Risk is highest in patients with multiple infusions, low baseline phosphate, or malnutrition.
Monitoring guidance
FDA now recommends measuring serum phosphate before and during treatment in patients at risk of hypophosphataemia. Consider supplementation or alternative iron formulations in patients who develop persistent low phosphate. The updated prescribing information is available on DailyMed ↗. For background on IV iron formulations see the StatPearls overview ↗.
FAQ
Does a Boxed Warning mean a drug is being withdrawn?
No. A Boxed Warning ↗ (also called a Black Box Warning) is the FDA's strongest label caution, but the drug remains on the market. It means the agency has determined that a risk is serious enough to require prominent, standardised labelling. The drug continues to be prescribed under appropriate clinical conditions. See the FDA's patient guide to Boxed Warnings ↗.
Where can I read the full updated label?
All current FDA-approved prescribing information is available on DailyMed ↗, maintained by the National Library of Medicine (NLM). Search by drug name to find the most recent label version. Historical label versions are also archived there.