Intravenous (IV) iron is used to rapidly restore iron stores and correct iron deficiency anemia (IDA) when oral iron is not tolerated, has an inadequate response, or is not feasible (for example, due to pregnancy or conditions that impair absorption such as gastric surgery or inflammatory bowel disease). IV administration is often preferred where faster repletion is needed or when oral therapy would be impractical or ineffective. Choice of a specific IV iron product is typically driven by the product's approved indications and labeling, the convenience of dosing (number of infusions needed to deliver the total dose), cost, and the agent's safety profile rather than large differences in efficacy between formulations. (See product prescribing information for age indications and dosing.)
Safety considerations play an important role in product selection. Hypersensitivity reactions, including anaphylaxis, are rare but can occur with all IV iron formulations; some products (iron dextran and ferumoxytol) carry boxed warnings for hypersensitivity and anaphylaxis. Infusion-related reactions are generally mild to moderate (eg, flushing, itching, chest tightness) but facilities should be prepared to manage uncommon severe reactions. Comparative studies and observational data have reported varying adjusted rates of anaphylaxis across agents, which has informed safety labeling and clinical choice.
Another key safety concern is treatment-associated hypophosphatemia. Ferric carboxymaltose (Injectafer) has been associated with a higher risk of clinically significant hypophosphatemia — including severe, symptomatic, and persistent decreases in serum phosphate — compared with several other IV iron preparations (eg, ferric derisomaltose/Monoferric, ferumoxytol/Feraheme, iron dextran). The mechanism is thought to involve stimulation of fibroblast growth factor 23. When selecting an IV iron product, clinicians should balance the convenience of larger single-dose regimens against the differing risks of hypophosphatemia and hypersensitivity, and monitor laboratory values as clinically indicated.
Relevant guideline and lab considerations: KDIGO guidance for adults with CKD supports IV iron when TSAT is < 30% and/or ferritin is < 500 ng/mL, and pediatric CKD thresholds are more stringent (eg, TSAT < 20% and ferritin < 100 ng/mL). For general IDA without CKD, commonly used ferritin thresholds to define iron deficiency are ≤ 15 ng/mL (age-dependent) and hemoglobin cutoffs vary by age and sex. Documentation to support coverage decisions should include clinical notes, diagnosis, medication history, and pertinent laboratory values demonstrating iron deficiency and treatment response. For re-authorization, a documented positive response is typically defined as an increase in hemoglobin of ≥ 2 g/dL from baseline and supporting lab results.