FDA Adds Boxed Warning Over Injectafer Low Phosphate Risk
The U.S. Food and Drug Administration has added its strongest safety warning to the labeling for ferric carboxymaltose injection, marketed as Injectafer, because the treatment can cause dangerously low phosphate levels in some patients.
What the FDA Changed
The FDA approved revisions to Injectafer labeling on September 1, 2026. The change adds a boxed warning describing the risk of symptomatic hypophosphatemia, a condition in which phosphate levels in the blood fall below a healthy range.
Phosphate is important for normal muscle and nerve function, energy production and bone health. The agency said severe or prolonged hypophosphatemia can cause serious complications, including osteomalacia, a condition that weakens bones and can contribute to fractures.
Patients Who May Need Monitoring
The FDA recommends phosphate monitoring in patients considered at risk for hypophosphatemia. Monitoring is also advised for patients who receive a repeat course of ferric carboxymaltose within three months of a previous course.
Symptoms can vary with the severity and duration of low phosphate levels. The FDA lists muscle weakness or pain, fatigue, tremors, confusion, seizures and abnormal heart rhythms among possible manifestations.
Why Repeat Treatment Matters
The warning is especially relevant for patients who need repeated intravenous iron treatment. Doctors may use intravenous iron when oral iron is not effective, not tolerated or not appropriate for a patient’s medical situation.
The new labeling does not mean that every patient receiving Injectafer will develop hypophosphatemia. Instead, it gives clinicians more prominent information about a known risk so they can identify vulnerable patients and monitor them when appropriate.
What Patients Should Know
Patients should not stop or change prescribed treatment without speaking with the clinician managing their care. Anyone receiving intravenous iron who develops unusual weakness, significant fatigue, confusion or other concerning symptoms should contact a healthcare professional.
People receiving repeat courses should also ask whether phosphate testing is appropriate based on their medical history and treatment schedule.
Broader FDA Safety Monitoring
The labeling change illustrates how the FDA uses post-market safety information to update warnings after medicines are already in clinical use. A boxed warning is intended to make serious risks prominent for prescribers and patients.
The agency’s announcement reinforces the importance of individualized monitoring rather than assuming that one treatment schedule carries the same risk for every patient.
Related Hudson Tribune coverage: New FDA treatment approval.
Source: U.S. Food and Drug Administration.
